For quite a long time, SyncMaster XL20 was sold alone - Samsung did not release other monitors with LED backlighting. However, of course, this situation could not last forever - and, again ahead of the competition, the company announced the release of the 24-inch SyncMaster XL24 and 30-inch XL30 models. Retail prices for them, of course, will not be as affordable as for the XL20 - but, taking into account the increased diagonal and the virtual absence of competitors, they still cannot be called exorbitant.
However, are low prices a sign of cheapening, which can negate the declared advantages of these monitors? And in general, what does extended coverage give us and what does it not give us? Is it worth overpaying for it compared to much cheaper monitors backlit with fluorescent lamps?
Today we can answer these questions: in our laboratory - Samsung SyncMaster XL24 and SyncMaster XL30.
Expanded color gamut: pros and cons
Theory, my friend, is dry,
But the tree of life turns green.
Goethe
We have already written in detail about what color gamut is, why most existing monitors have it relatively modest and how it can be expanded in the article “ Parameters of modern LCD monitors: objective and subjective", with the corresponding section of which I encourage you to get acquainted.
In theory, of course, a larger color gamut is a clear and undoubted benefit: it allows the monitor to display colors that are, in principle, inaccessible to monitors with a smaller gamut. This is where confusion sometimes arises with the concept of “number of colors” found in the description of any monitor - usually 16.2 or 16.7 million. Color gamut and number of colors are two complementary things: color gamut determines what range of colors the monitor can display, and the “number of colors” parameter determines how many gradations it can divide this range into in order to display intermediate shades and halftones. These two parameters do not directly affect each other: theoretically, you can make a monitor with four colors and a huge color gamut, it will simply show only pure green, pure blue, pure red or white - without any halftones - but these colors will be very clean indeed.
Thus, on a monitor with a large color gamut, you can get cleaner, richer colors even if you use a prehistoric video card with 16-bit representation or are a convinced fan of the operating system Windows systems 3.11 for Workgroups. Color gamut is a hardware characteristic of a monitor that does not depend in any way on what system it is connected to.
However, although there is no mutual influence between the two mentioned parameters, in some situations they should be considered together. Obviously, the “number of colors” parameter determines how much different two neighboring colors are - the greater the number of colors, the smaller this difference. The entire space of colors reproduced by the monitor is divided into 16.7 million steps - and we can set a specific color only with an accuracy of a specific step.
Accordingly, if this space - that is, the color gamut - increases, but the number of steps remains the same, then the difference between two adjacent steps inevitably increases. It turns out that, on the one hand, a monitor with a larger color gamut can show more colors in the physical sense of the word - but, on the other hand, it does it less accurately. In practice, such a lack of the number of colors is noticeable on smooth gradients: transverse stripes appear on them, each of which corresponds to one step.
Actually, even with today’s standard 24-bit color representation (video cards usually operate with the concept of 32-bit, but in fact in this case only 24 bits are still allocated to describe color - the remaining eight are used for auxiliary needs and were generally introduced only because it is “more convenient” for video cards to work with 4-byte numbers than with 3-byte ones) you can notice this effect: stretching, say, a gradient from red to black across the entire screen, you will see narrow uniform transverse stripes on it even on the best LCD monitor (bad monitors can also add wide and uneven stripes).
On monitors with an extended color gamut, the effect of banding in gradients with the same 24-bit color will become slightly more noticeable.
The only possible solution, of course, is to increase the color bit depth - up to 30-bit, in which 10 bits are allocated to each of the three components. This way we will increase the number of colors, reduce the size of the steps and are guaranteed to get rid of any problems with gradients.
Alas, although this is not the first generation of video cards that support 30-bit color transmission via the DVI interface in hardware - for example, ATI cards, starting with the X1000 series models - it is still difficult to call this more than exotic. Only a few monitors - such as the NEC SpectraView Reference 2180WG LED costing more than 150 thousand rubles - support a 30-bit interface, and from the software side the situation is not much better.
And although the problem of a lack of colors on monitors with extended gamut cannot be called serious - for home users it is generally insignificant - its presence cannot be denied either: we are talking about professional monitors that can be used in areas such as pre-press preparation and screen proofing, where Even small errors in color display can play a role.
- Joe, devices!
- Six hundred!
- What, “six hundred”?..
- What about “devices”?..
Another, more significant problem is that when working with color, both the software, the video card, and the monitor operate not with physical units of measurement, but with certain conventional units - from 0 to 255 for each of the three basic colors. (0; 255; 0) is not green, it’s just a set of numbers; It will become green only after we accept as a rule that on the monitor such a set corresponds to the lighting of the green subpixel.
The problem is that the green subpixel on a regular monitor and on a monitor with extended coverage have different colour. In the latter case, he is... uh... greener. That is, cleaner, richer. If you put such monitors next to each other and display a color with the symbol (0; 255; 0) on them, then on a monitor with extended coverage it will look pure green, but on a monitor with normal coverage you will find a quite noticeable yellowish tint.
In other words, the function of converting a conditional value (number) into a physical one (a specific color visible to the eye) is performed by the LCD matrix of the monitor. However, the matrices are different, and the software in most cases focuses on the same standard, called “sRGB”.
As a result, on monitors with extended gamut - and it expands precisely relative to the standard sRGB gamut - when displaying images prepared for sRGB using software that focuses only on sRGB and is not aware of the existence of other monitors, colors will be distorted. The monitor will simply “stretch” the image, oriented to the sRGB gamut, to its own color gamut - in this case, not only pure colors will shift, but also all halftones; the only exceptions will be white and gray colors - they will look correct on any monitor, unless, of course, the monitor is configured too poorly in general, regardless of coverage.
The most typical case of monitors with extended coverage are models with lamps with improved phosphor, which differ from conventional sRGB monitors in a more saturated green color. Accordingly, all the halftones on them will be slightly shifted - in the figure above this shift is approximately shown by white arrows (the black triangle is the standard sRGB gamut, the white triangle is the actual gamut of the monitor with improved backlight lamps, to which images prepared for sRGB will be “stretched”) .
However, people familiar with any measuring equipment, they will immediately notice: in fact, any measuring device works exactly the same as a monitor - it represents any conventional values in the form of physical quantities. Even ordinary mechanical bathroom scales show us In fact not the weight, but the angle of rotation of the arrow - but we know how this angle depends on the weight, and therefore we can place a scale under the arrow indicating kilograms, not degrees.
Is it possible to perform such a procedure with a monitor so that the software for working with images has the ability to adjust the picture to the color gamut of the current monitor? Yes, and this procedure is called “hardware calibration”.
Hardware calibration of monitors
Strictly speaking, it would be more correct to write “hardware calibration of an image reproduction system consisting of software, a video card and a monitor” - however, it is difficult to pronounce such a phrase, and in practice, of the three components indicated, only the last one, that is, the monitor, is initially imperfect. The video card and programs do not introduce any distortion by default. Accordingly, it is quite reasonable to shorten the phrase to two words: “monitor calibration.”The word “hardware” means that a special device is used for calibration, a calibrator, which is a sensor attached to the monitor screen that records the color and brightness of the light.
During the calibration process, the software supplied with the calibrator displays fields of different colors underneath it - usually white, black, sometimes several shades of gray, and also in turn from black to red, green and blue with a certain step. The calibrator records what color is actually displayed on the screen - accordingly, it allows us to calculate a correction that brings the monitor characteristics to the ones we need.
The use of a separate device here is absolutely logical - without a calibrator, we can only send a certain signal to the monitor, but we cannot get feedback on how it reacted to this signal (that is, what color it showed).
Calibration is extremely simple from the user’s point of view: you just need to hang the calibrator on the screen, launch the software supplied with it and answer a few questions regarding the desired monitor parameters - the process itself occurs in a fully automatic mode and takes ten to fifteen minutes. After finishing, the calibrator can be removed from the monitor - next time you will need it if the calibration results no longer suit you (for example, the monitor settings or the lighting in the room change).
Calibration can be used for three purposes, which we will arrange in order of increasing complexity.
Definition of color gamut
To do this, it is enough to measure which colors the monitor reproduces under the guise of pure red, pure green and pure blue - that is, at the output we get the coordinates of the vertices of the color gamut triangle. Then this information is written to an ICC file, the so-called profile, associated with a given monitor, and can be used by any user programs.
In this way, we solve the problem described at the end of the previous section - if our program knows the color gamut of the monitor and knows what gamut the picture it reproduces was optimized for, it can adjust it so that on this monitor the colors look as intended by the author of the picture. Let’s say, if the “green scale” on our monitor with extended coverage is stretched by 10% relative to the sRGB coverage, then in an sRGB picture, before displaying it on the screen, we need to reduce the green scale, on the contrary, by 10% - as a result, we will see colors on the screen like this , as they should have been, without any shift to green. This approach allows you to simultaneously take advantage of monitors with a large coverage for processing images prepared specifically for them, and not experience any inconvenience when working with ordinary sRGB images.
But, of course, a number of obstacles stand in our way. Firstly, not all programs, even those specifically designed for working with images, can use data about the monitor’s color gamut. Of course, with professional packages like Adobe Photoshop, there are no problems here - but with simpler programs, for example, numerous picture viewers, things are much worse.
Secondly, having just a monitor profile is not enough - you also need to know what color gamut each specific picture was optimized for in order to decide whether it needs to be adjusted in any way when displayed on a given monitor. Theoretically, such technology exists - in files JPEG formats and TIFF, you can implement ICC profiles that indicate the “native” color gamut of the image - in practice, most images do not have this profile, and most programs still do not know how to use it.
Specifying a monitor profile in XnView
However, there is hope: let's say Firefox browser 3.0, although not a specialized program for viewing images, already supports color management using ICC profiles. Many cameras also allow you not only to embed a color profile in JPEG files, but also to save images with the AdobeRGB gamut, which provides better reproduction of the green color and is well compatible with monitors with an extended color gamut - fortunately, the hardware of the camera matrices allows taking pictures with a larger color gamut, and their conversion to sRGB is carried out for the sake of compatibility with existing sRGB monitors.
Selecting a color space in the Canon EOS-350D
Thus, we are slowly but surely moving towards ensuring trouble-free operation of monitors with different color gamuts through the widespread use of ICC profiles. However, in the meantime, accurate color display on wide-gamut monitors requires some care in choosing and configuring software.
Determining white balance
There is no universal white color in nature; our brain chooses a specific color as white depending on the lighting conditions: from the evening twilight the windows of houses seem yellow to us, and from the house the twilight appears blue.
Accordingly, to prevent your monitor screen from appearing bluish or reddish, you need to adjust the balance of blue and red colors in accordance with the lighting in your room - this is what is called adjusting the color temperature.
Although the procedure seems trivial, on LCD monitors it is complicated by the fact that most of them do not have temperature settings as such, but only three independent sliders for red, green and blue, the optimal ratio between which you can choose yourself.
The calibrator allows you to solve this problem automatically: you just need to tell it which color temperature you want to receive on the screen, and it, having measured the current temperature of the white color of the monitor, will calculate and make the appropriate changes to the video card settings. Some models - for example, older versions of ColorVision Spyder - have a mode in which the calibrator helps to correctly adjust the sliders R-G-B monitor manually, showing you the current balance of these three colors and suggesting which of them should be reduced or increased in order to get the desired result.
Correction of gamma curves
In each of our articles, in each test of an LCD monitor, you can find one, and often several graphs of the so-called gamma curves - showing the relationship between the digital signal coming to the monitor from the video card and the actual pixel brightness that this signal set. Ideally, for a standard monitor, the curve should have the form y=x^γ, where the gamma index is γ=2.2. Such an exemplary curve is indicated in black on the graph.
Ideally, the curves for red, blue and green colors exactly coincide with the reference one, merging into one thick line on the graph. This means that from this point of view the monitor is configured perfectly - but, alas, there are sadly few such monitors.
Much more common is the case presented in the second graph: if green and red colors more or less coincide with the ideal, then blue has noticeably fallen down. This means that if we try to display any shade of blue on the screen, we will get a darker picture than we expected based on the standard gamma value of 2.2. If we derive a certain tone (including just gray), formed by mixing all three colors, then it will be shifted to the red-green region - again due to the lack of blue.
In part, the situation is reminiscent of the color gamut problem described above - the programs we use by default assume that the monitor meets some standard requirements (sRGB color gamut, gamma index 2.2), but in practice this is not the case. There is some difference in the methods of solving problems: if a large color gamut does not need to be corrected, but only taken into account when displaying images, then there is no benefit in gamma curve deviations - and it is best to immediately correct them at the level of the video card or the monitor itself. The software should by default assume that the monitor has a gamma value of 2.2.
To correct the curves, a calibrator is again used: under its sensor, a series of halftones from the darkest to the lightest are displayed on the screen, for each of which the necessary correction is calculated - thus, the gamma curve is checked and corrected at a certain number of points. Based on the results of measurements, a correction table is created, which is loaded into the video card - after which our entire video system receives a guaranteed gamma value of 2.2 and neat curves. In this case, no additional actions are required on the part of the user software; the calibrator’s own software is responsible for receiving and loading data into the video card. Of course, every time you restart the computer, the table must be loaded into the video card again, so the calibrator software must be installed on the system on an ongoing basis - although the actual calibration process can only be carried out from time to time, once every few weeks or months.
In principle, the gamma curves of a monitor can be corrected without the help of a calibrator, but this will require painstaking adjustments, and the result will not be so accurate. However, those interested can familiarize themselves with the methodology using the link.
Above I wrote about loading correction tables into a video card - this is the most common case, but not the only one. Some professional monitor models allow you to load correction tables directly into them, leaving the video card untouched. This approach slightly increases the accuracy of calibration and, accordingly, the color rendition of the monitor - in addition, there is no need for software that loads the correction table every time the computer is turned on: once loaded, the table is stored in the monitor until the next calibration.
Natural Color Expert and XL Series Monitor Calibration
The Samsung SyncMaster XL24 and XL30 monitors we are reviewing today belong precisely to the latter group - data with calibration results can be loaded into the monitor itself.
Of course, the program performing the calibration must be able to use this opportunity - therefore, it will not be possible to use the first calibrator that comes to hand. Fortunately, the monitors already come with the X-Rite Eye-One Display 2 calibrator, a model well known among people working professionally with color. The calibrator comes with the Natural Color Expert program.
Eye-One is a small device that is hung on the monitor screen (you saw a photo of the calibrator in action just above in the text), it is held on by a USB cord thrown across the monitor, and a large number of small suction cups placed in two circles on the device pressed against the screen. calibrator surface. By themselves, without the help of a USB cord, the suction cups cannot hold Eye-One on the screen, because they are too weak for this; their role is to ensure a tight fit of the calibrator to the surface of the matrix.
In the center there is a photo sensor window (more precisely, several photo sensors, in front of each of which there is a filter of a certain color), along the perimeter of the calibrator there is a strip of soft porous rubber that prevents extraneous external light from reaching the sensors.
The Natural Color Expert program is a replacement for the native software of X-Rite calibrators and is intended to work only with monitors Samsung series XL - accordingly, you will not be able to use the calibrator on other monitors with it.
After starting calibration, the program displays sequential rectangles of black, red, blue, green and white in the center of the screen, under the calibrator. There is no progress indicator, only flower petals spinning in the lower right corner next to the inscription “Reading Monitor” - however, the whole process takes only a few minutes. Once completed, the calibrator can be removed from the screen.
Alas, even from this description it is clear that of the three points described in the previous section of the article, the calibrator on the XL24 and XL30 performs only two - color temperature correction and color gamut determination. Despite the fact that with my family software(i1 Match) Eye-One is a full-fledged calibrator, capable of also determining the shape of gamma curves and, if necessary, adjusting it, in Natural Color Expert this functionality is removed - perhaps license agreements with X-Rite, which made it possible to sell this rather expensive device complete with monitors at a minimal markup.
What, then, is the possibility of recording correction data in the monitor, which I mentioned at the beginning of the article, and in general - the point of using a calibrator with reduced functionality?
In the previous section, speaking about monitors with an extended color gamut, as a way to work correctly with them, I only mentioned creating ICC color profiles and using them in user software. However, XL series monitors provide another opportunity: they can emulate in hardware any color gamut up to their own. However, let's take it in order...
The first operating mode of NCE – “Calibration” – allows you to set all the basic monitor settings, except for the color gamut. You can calibrate the monitor to a certain brightness, set the desired color temperature and gamma indicator. If necessary, this allows you to calibrate several monitors so that the image on them is the same - if you simply set the same settings in the on-screen menu, there will be a difference due to the spread of parameters between different instances, but the calibrator allows you to minimize this difference.
After calibration, you receive a window with the measurement results: coordinates of the corners of the color gamut triangle, color temperature and deviation of white color in ΔE units from the desired one, as well as brightness and contrast (more precisely, the level of black color - contrast, respectively, will be equal to the ratio of the levels of black and white , that is, in this case 121/0.11 = 1100:1). After clicking the “Save” button, an ICC file is created in the C:\Windows\system32\spool\drivers\color directory, which is linked in the system to the current monitor - any programs that support color management can use it to obtain reliable information about the monitor and the corresponding correction of images before output.
But what to do if for some reason the program you need cannot use ICC profiles? For this purpose, the following NCE operating mode is provided – “Emulation”.
At first glance, there are almost no differences from the “Calibration” mode, but pay attention to the upper part of the screenshot: a line appears there indicating the path to the ICC file. No, this is not a file in which NCE will save the measured parameters of the monitor after calibration - this is a file in which NCE itself will adjust the parameters specified in it.
You can set the same parameters without a profile: under the color temperature selection bar, windows have appeared with the coordinates of the vertices of the color gamut triangle, which can be set manually.
Let's say, for one reason or another, you use a program that only works correctly with sRGB monitors. In this case, you load the usual, standard sRGB profile into the “Emulation” mode, start calibration...
...and after its completion, NCE asks you whether it is worth recording the result in the monitor? By agreeing, you get an LED-backlit monitor with a wide color gamut hardware room emulation of standard sRGB coverage, activated by pressing one button.
In total, XL series monitors have five emulation modes:
“Custom”: all manual settings are unlocked, color gamut is maximum, brightness is manually adjustable, emulation of anything is disabled.
"sRGB": Color gamut, brightness, gamma and color temperature are set according to the sRGB standard.
"AdobeRGB": Color gamut, brightness, gamma and color temperature are set according to the AdobeRGB standard.
“Emulation”: color gamut, brightness, gamma and color temperature are set manually in the section of the Natural Color Expert program of the same name.
“Calibration”: brightness, gamma and color temperature are set manually in Natural Color Expert, color gamut is the maximum possible for the monitor.
What's also interesting is that while sRGB and AdobeRGB modes are preset at the factory, they can also be re-set using a calibrator to correct any inaccuracies or drifts in the monitor's settings as it ages. To do this, you need to load a standard sRGB or AdobeRGB ICC profile in Natural Color Expert in the “Emulation” tab - then, after calibration is completed, the program itself will offer to save the result in the monitor mode corresponding to the loaded profile.
If we consider these modes from the point of view of practical use, then “Custom” gives you access to all the monitor settings, which can be changed whenever and however you want, but is the least accurate in terms of color rendition. “sRGB”, “AdobeRGB” and “Emulation” allow you to emulate in hardware two standard and one arbitrary mode with limited color gamut for use on the monitor in cases where the correction of output images for an expanded gamut on program level impossible or undesirable. The last mode, “Calibration”, is needed to obtain the most accurate color rendition in programs that can take into account the color gamut of the monitor and correctly adjust the displayed images in accordance with it.
The last tab, Natural Color Expert, can be said to be a service one: here you manage the created ICC profiles, from here you can start measuring the current monitor parameters (without creating a profile and without changing any settings), turn on a warning about the need for recalibration after a specified period, and also reset the settings of the “sRGB” and “AdobeRGB” modes (if you changed them as described in two paragraphs above) to factory settings.
So, briefly about what Natural Color Expert allows and does not allow when paired with the Eye-One Display 2 calibrator and the SyncMaster XL20 monitor:
allows you to: adjust the monitor to a given brightness, contrast, color temperature, gamma and color gamut, while simultaneously creating the corresponding ICC file;
does not allow: adjusting the shape of gamma curves.
How important is the last point? It all depends on how accurately the gamma compensation is set up initially and, accordingly, whether it needs correction - and we will find out this by testing the monitors themselves...
Samsung SyncMaster XL24
The XL family of monitors began with the relatively modest, by today's standards, 20-inch XL20 - and only after quite a long time did Samsung release larger models, starting with the 24-inch XL24.The monitor is built on a widescreen S-PVA matrix with a resolution of 1920x1200, has LED backlighting and a color gamut of 123% NTSC (for comparison, conventional desktop monitors have a coverage of about 75% NTSC, laptops - 45% NTSC). The maximum rated brightness of the monitor is 250 cd/sq.m, contrast is 1000:1, response time is 8 ms (GtG), viewing angles are 178° horizontally and vertically.
The monitor has a fairly typical design for “working” Samsung models, except that it is slightly larger than usual. The body color is matte black, in the lower left corner the inscription “LED” lined with metallized dots shines.
A removable light-protective visor is supplied with the monitor. The canopy is of excellent quality: metal, painted with matte black paint on the outside and covered with black velvet on the inside.
In addition, the kit includes the already mentioned X-Rite Eye-One Display 2 calibrator with Natural Color Expert software, a DVI cable, a power cord and instructions.
When I wrote above about the dimensions of the monitor, I, of course, had in mind the thickness of the case - even with a quick glance from the side it becomes obvious that the XL24 can hardly be called thin. The reason primarily lies in the high heat generation of LED backlighting - it is less economical than fluorescent lamps, and therefore requires more serious cooling.
But how, you ask, does LED backlighting on laptops save energy?! The fact is that the principle of operation in these two cases is different: desktop monitors use triads of red, blue and green LEDs, which are not economical, but provide a large color gamut, while laptops use white LEDs, which are economical, but do not provide any gain in coverage .
Moreover, in the XL24 you even have to use a fan to cool the backlight! It is located on the back of the monitor, next to the connectors, and works quite quietly - at least in an office room you can’t hear it at all, but at home, if yours is quiet enough system unit, you can only hear a faint rustle.
The monitor stand allows you to adjust the angle of the screen, its height (ranging from 120 to 220 mm, if you count from the table to the bottom edge of the matrix), as well as rotate it around a vertical axis and turn it into portrait mode. If desired, the standard stand can be removed and replaced with a VESA-compatible bracket.
The monitor has two DVI connectors - digital DVI-D and universal DVI-I, to which you can connect the analog output of a video card via an adapter (although I would not recommend such a connection for a 24" monitor). Next to them you can see the input of the built-in USB hub.
The corresponding USB ports - four of them - are located on the side, in two groups of two ports. In each pair, the ports are pressed against each other, so that only cables and very thin flash drives will fit into them at the same time. However, this is not critical - in fact, in most cases, two USB ports would be enough on the monitor.
The control buttons are located in a row at the bottom right of the front panel; the inscriptions on them are made in white paint and are clearly visible even in semi-darkness. The buttons provide quick – without going into the main menu – access to switching color gamut modes (the “Mode” button, I wrote about the modes in the previous section of the article), adjusting brightness and contrast, as well as switching inputs and auto-adjusting to the signal when connected to an analogue device.
When working, the power button is highlighted in white, and just below, on a seemingly opaque strip, the name of the current monitor color gamut mode lights up. If such illumination bothers you, you can turn it off from the monitor menu.
The on-screen menu is standard for Samsung monitors; it has not undergone any changes due to the “professionalism” of the XL24. It would seem, why change it, because it is convenient and understandable?
The fact is that in professional models it is customary to express the values of various parameters in physical quantities whenever possible. If this is color temperature, then it is in Kelvin. In the photo above we see the menu for setting the color temperature in the XL24, where it is indicated by names that say nothing about specific numerical values. Well, yes, warm... but how long is warm? 6000 K? 5400 K? More? Less? No answer.
It is clear that if the kit includes a calibrator that allows you to accurately set any desired temperature, this is not a problem - but still an unpleasant aftertaste remains.
The manual temperature setting mode is also not encouraging: here we are asked to “by eye” set the balance between red, green and blue colors. For comparison, professional NEC monitors (UXi series) allow you to adjust the temperature directly in Kelvin, and the ColorVision Spyder3Elite calibrator has a special mode that allows you to adjust the monitor settings not by eye, but precisely - alas, the combination of XL24 and Eye-One Display 2 does not has neither the first nor the second possibility.
Among the expanded menu options, one can only note the disabling of the indication LEDs on the front panel.
By default, the monitor brightness is set to 70%, contrast – to 80%; to achieve a white level of 100 cd./m2 we had to reduce both values to 60%. Of course, brightness and contrast are adjusted by menu settings only in the “Custom” mode - in other modes they are set during calibration in Natural Color Expert. The brightness is controlled by pulse-width modulation of the power supply to the backlight LEDs at a frequency of about 1.4 kHz.
Smooth gradients are transmitted perfectly, without the slightest flaws.
Of course, the most interesting question in objective, instrumental testing of XL series monitors is measuring the color gamut. Although the overall testing was conducted with the ColorVision Spyder Pro calibrator, the color gamut was measured using the Eye-One Display 2 included with the monitor - the fact is that the ColorVision calibrators of models below the Spyder 3 do not correctly determine the green coordinates on monitors with an extended color gamut.
To see how well the monitor emulates other color gamuts, we switched it to sRGB mode. As you can see, the result is excellent: the white (measured monitor coverage) and black (standard sRGB coverage) triangles simply coincide. Please note that in this mode, the image on the XL24 will be slightly different from the image on monitors with fluorescent lamps - the latter does not have the same coverage as sRGB in red and green. However, if desired, in the “Emulation” mode and the XL24 can be calibrated so that it corresponds to any specific real monitor.
The same result was obtained in the “AdobeRGB” mode – the XL24 coverage exactly coincided with the standard AdobeRGB coverage.
On white, the backlight uniformity is simply excellent: the average deviation is 1.4%, the maximum recorded is 6.1%, that is, 3-4 times better than most models. Most likely, the monitors are individually adjusted at the factory to level the backlight (a similar technology is also found in professional NEC models) - this is supported by the fact that on a black color, where such an adjustment is impossible, clear backlight spots appear on the screen, and the unevenness indicators noticeably worsen : 4.6% on average and 26.4% at maximum.
The gamma curves look good by the standards of regular monitors, but not good enough for a professional monitor - the gamma indicator is a little too high, as a result of which the curves are below exemplary. In practice, this will result in a slightly darker and more contrasty image.
Interestingly, in the “AdobeRGB” mode the monitor is tuned better: all three curves rise, almost merging with the ideal one. However, the blue curve is still somewhat different from what is desired.
Unfortunately, in the sRGB mode, the quality of the gamma settings is something average: better than in Custom, but worse than in AdobeRGB.
Just for fun, we tried to run calibration of this mode from the “Emulation” section of Natural Color Expert:
The result was as expected: as I wrote above, Natural Color Expert simply does not try to correct the shape of the gamma curves. Accordingly, the schedule has remained almost unchanged. Calibrating the monitor with the “native” calibrator software gives a noticeably better result - but in this case, the correction table is written to the video card, and not to the monitor.
The monitor has 12 preset color temperature settings in the “Custom” mode, not counting the manual settings – but, unfortunately, these settings are named with conventional names like “Cool3”, and not with specific numerical values. In sRGB and AdobeRGB modes, the color temperature is fixed. In the “Calibration” and “Emulation” modes, it is set in Natural Color Expert, so we did not include them in the table below.
Alas, the quality of the settings is not very encouraging: for professional monitors, such a spread in color temperature between different gray levels is considered very large - for comparison, in the NEC MulstiSync LCD2190UXi monitor it ranges from tens to, at most, several hundred degrees, but here sometimes it goes off scale by two thousands. The “sRGB” mode on average demonstrates a color temperature corresponding to the standard of the same name (about 6500 K), but for some reason “AdobeRGB” turned out to be colder - in theory, it should have the same 6500 K (or, to be more precise, the D65 illuminator) , in practice the temperature turned out to be about 7000 K. However, this can be corrected using calibration.
One of the known problems with LED-backlit monitors is the uniformity of color temperature across the screen field. The reason for the problem lies in the use of a large number of LED triads: if the parameters of the LEDs are slightly different in different triads, then these triads and the light will produce slightly different ones.
To check how current it is this problem for SyncMaster XL24, we measured the white color temperature at 25 points on the screen:
Well, the problem cannot be denied: the spread was about 400 K. In other words, the monitor shows a difference in temperature not only between different gray levels, but also between different points on the screen. In principle, the problem can be solved either by careful selection of LEDs, or by individual factory settings for each instance, in the same way as is done to equalize the uniformity of illumination on white, but, alas, in our case such settings were not made.
The maximum brightness of the monitor was about 200 cd/sq.m, the contrast was 400:1. Let me remind readers that we measured these values using the ColorVision Spyder Pro calibrator, which gives slightly underestimated results. In the “sRGB” and “AdobeRGB” modes, the brightness sufficiently meets the requirements of the standards of the same name, but the contrast is disappointing - the black level in “AdobeRGB” is as much as 2.77 cd/sq.m, while the standard is approximately 0.56 cd/sq.m .m. Of course, both parameters - brightness and contrast - can be adjusted when calibrating the monitor in the “Emulation” mode, but I would like them to be normal from the very beginning.
And finally, response time. Although the XL24 is built on an inherently slow PVA matrix, it is equipped with a response time compensation circuit - and as a result, the performance is quite normal even for games, not to mention work. The average measured response time was only 6.7 ms (GtG), the maximum recorded value was 16.5 ms.
Unfortunately, there are also accompanying artifacts - in the form of light or dark borders around moving objects. The average “miss” level of the compensation scheme is 9.0%, the maximum recorded is 42.9%. These values can be called average, but nothing more: in most cases, artifacts will not bother you, but you can notice them if you want.
This concludes my testing of the SyncMaster XL24, but before we draw any final conclusions, let's look at the next model, the 30-inch XL30...
Samsung SyncMaster XL30
Starting small with the 20-inch XL20, Samsung next took its LED-backlit monitor lineup to its logical conclusion, at least in terms of diagonal size, with not only the XL24, but also the 30-inch XL30.Its parameters, minus the screen size and resolution, are similar to the XL24 - the monitor is built on a 30" S-PVA matrix with a color gamut of 123% NTSC, a resolution of 2560x1600, a maximum brightness of 200 cd/sq.m, a contrast ratio of 1000:1, response time of 6 ms (GtG) and viewing angles of 178° in any direction.
A high resolution imposes a limitation on the video card and cable used - they must support the dual-channel Dual Link DVI interface, because otherwise you will not be able to “squeeze” more than 1920x1200. However, this is not a problem: the corresponding cable comes with the monitor, and is already found in stores literally on every corner, and all video cards of the last at least three generations have a DL-DVI output. However, based on my experience, I would not recommend taking very cheap video cards - although formally they support DL-DVI, in practice sometimes problems arise with image quality. It is definitely not possible to connect the XL30 in native resolution only to video cards and laptops integrated into the chipset - both of them have one DVI channel and do not support resolutions higher than 1920x1200.
However, the interpolation on the XL30 is configured so that at a resolution of 1280x800 the image is absolutely clear - all the lines simply double their thickness. So, if there is an urgent need, you can work more or less normally with the monitor on SL-DVI video cards.
SyncMaster XL30 is quite large and quite weighty, at least by the standards of LCD monitors - about 14 kg. The case design is completely similar to the XL24, the color is matte black.
As with the XL24, the thick body is due to the need to accommodate and cool the LED backlight. If you compare these two monitors with regular Samsung models with a similar design (for example, SyncMaster 215TW or 225BW), you can see that between the back and front walls of the case in the XL series there is an additional insert that increases the thickness of the monitor.
The stand allows you to adjust the angle of the screen, its height (ranging from 90 to 170 mm), as well as rotate the monitor around a vertical axis and turn it into portrait mode. If necessary, the stand can be removed and replaced with a standard VESA bracket - of course, designed for a weight of at least 15 kg.
The monitor only has a DVI-D connector, analog connection impossible in principle. Next to the video input there is a USB hub - it has four ports in total, two of which are located right there on the rear panel.
Cooling the XL30 also requires a fan, but here it is hidden deep in the case - only numerous grilles are visible from the outside.
The remaining two USB ports are located on the side of the rear panel; they can be used to connect flash drives - although not very convenient, since you can find the ports either by touch or by actually looking behind the monitor.
The controls for 30" monitors - the XL30 is no exception here - are quite simple: there is no on-screen menu at all, there is only brightness adjustment. Most likely, the reason lies in the insufficient performance of the monitors used currently processors that are not capable of fully processing about 5.5 Gbit/s of information, taking into account user settings in real time.
However, the XL30 is still slightly different from other 30" monitors - the presence of a “Mode” button that switches color gamut emulation modes. Selected in this moment The mode is displayed on the panel below the buttons. The set of modes is the same as the XL24 - one without calibration, one with calibration and the maximum available color gamut, and three with emulation of different gamuts.
The brightness of the monitor is controlled by PWM modulation of the power supply to the backlight LEDs at a frequency of about 1.4 kHz.
The monitor comes complete with a metal light-protective visor, lined with black velvet on the inside, an X-Rite Eye-One Display 2 calibrator, and Natural Color Expert software.
In the "Custom" and "Calibrated" modes, the monitor's color gamut exceeds the standard gamuts of both sRGB and AdobeRGB - except that the very edge of the latter extends slightly beyond the monitor's gamut. As with the XL24, the difference in the quality of red color reproduction is immediately noticeable, as the XL30 looks so much cleaner and richer than on conventional fluorescent-backlit monitors.
The XL30 also has no problems with emulating standard color gamuts: the diagram above shows how closely the “sRGB” mode matches the real sRGB gamut - two triangles overlap each other. Again, note that the sRGB mode on the XL30 will be slightly different from real monitors - simply because the latter don't quite match the standard sRGB gamut. If necessary, the XL30 can be calibrated using Natural Color Expert for any color gamut, including those that match any fluorescent-illuminated monitor.
The situation with backlight uniformity repeats that of the XL24: apparently, the monitors are individually adjusted to even out the backlight on a white background, while this is technically impossible to do on a black background. As a result, backlight unevenness on white is 3.4% on average and up to 10.7% at maximum, while on black the values are worse - 6.2% and 23.8%, respectively.
The gamma curves in the “Custom” and “Calibrated” modes are not very accurate - if at the beginning of the graph they coincide well with the ideal curve, then then they suddenly go down, making the corresponding halftones darker than necessary.
But in the “AdobeRGB” mode the situation suddenly improves – there are differences between the real gamma curves and the reference one, but they are barely noticeable. It’s interesting that exactly the same situation happened with SyncMaster XL24 – the “AdobeRGB” mode was configured better than the others.
The monitor doesn't have a menu-based color temperature setting, so we were limited to measuring temperatures in Custom, sRGB, and AdobeRGB modes at default settings—though Natural Color Expert can calibrate the monitor to whatever temperature you want. The temperature spread between different gray levels turned out to be quite acceptable, except that in the “sRGB” mode the darkest color suddenly became warmer.
The absolute temperature is not set very carefully: in both “sRGB” and “AdobeRGB” modes it should be about 6500 K, but in practice it turned out to be 500 K higher in the first case and a thousand higher in the second. However, this drawback can be corrected by calibrating the monitor in Natural Color Expert.
Unfortunately, the pleasant impressions of the more accurate color temperature settings, compared to SyncMaster XL24, were spoiled by the results of measuring uniformity over the screen area: the difference in white color temperature between two points can reach almost 900 K - a reddish warm spot appears on the lower right edge of the screen.
Brightness levels are as expected in both manual mode (despite the lack of contrast adjustment, the monitor's brightness can be reduced to a level comfortable in normal ambient lighting) and in sRGB and AdobeRGB emulation modes. Let me remind our readers that these standards describe not only the color gamut, but also the brightness of the monitor - 80 cd/sq.m in the first and twice as much in the second.
Despite the same rated response time as the XL24, in practice the XL30 turned out to be almost twice as slow: an average of 12.4 ms (GtG), with a maximum of 26.8 ms. The monitor cannot be called completely slow; such performance is quite enough even for games - at least for not too demanding players - but it is not fast either. About the same real speed demonstrate the currently popular inexpensive 5 ms monitors on TN matrices.
At the same time, the magnitude of artifacts associated with “misses” of the response time compensation system decreased slightly compared to XL24 (on average - 8.8%), but their nature changed noticeably. The latter is that on a significant part of halftones there are no artifacts at all, on light halftones they are insignificant, but when a dark gray object moves over a black background, it can acquire a completely visible light border. However, this does not interfere at all during work; you can only notice the effect in games.
Conclusion
Well, the situation with monitors with LED backlighting - although we only looked at Samsung products, they essentially exhaust the market for relatively inexpensive LED BLU models (we are not considering ViewSonic VLED221wm because of the TN matrix in it, NEC SpectraView Reference 2180WG- LED – due to the very high price) – is somewhat ambiguous.On the one hand, these monitors really have a magnificent, stunning color gamut - I have not seen any other model that could show at least comparable purity and saturation of green and red colors. Monitors with conventional fluorescent lamps (color gamut about 75% NTSC) lag catastrophically behind, monitors with lamps with improved phosphor (coverage 97% NTSC) are more or less close to LEDs in terms of the quality of green color reproduction, but are completely incomparable with them in terms of red reproduction quality.
It’s absolutely impossible not to notice the difference; you just need to put two monitors – a regular one and one with LED backlight – next to each other. To imagine the difference without having the latter, place a laptop (45% NTSC color gamut) and a desktop monitor (75% NTSC) side by side and display the same picture on their screens with bright, pure colors - the “LED” monitor is just as superior "fluorescent" is how "fluorescent" is superior to a laptop.
Moreover, in addition to pure red and green, the transmission of turquoise and yellow flowers– the latter is especially appreciated by printers who do not like the pale yellow color of conventional monitors.
However, you need to understand that pure, bright colors are not yet accurate color rendition. Yes, LED-backlit monitors can display colors that are fundamentally impossible for fluorescent-lit monitors - but this alone does not guarantee that the colors will be displayed accurately. During testing, we found a number of problems, some fundamental, some specific to the SyncMaster XL series.
Firstly, despite the inclusion of the Eye-One Display 2 calibrator, the Natural Color Expert software supplied with the monitor does not do one important thing: it does not correct flaws in the shape of the gamma curves and, accordingly, in the accuracy of halftones. Yes, the calibrator makes it very easy to work with the monitor - it allows you to literally adjust the color temperature, brightness, contrast and color gamut to suit any necessary conditions in literally five minutes, without making any special effort - however, the ability to accurately correct the gamma curves would not be superfluous , because initially the monitors are not configured ideally.
Secondly, and this is one of the biggest problems with “LED” monitors, color temperature changes not only between different gray levels, but also between different points on the screen - due to the variation in LED parameters in different triads. Since each triad illuminates its own section of the screen, a colder zone will appear where the blue LED is a little brighter, and a warm zone will appear where the red LED is a little brighter. This problem can be corrected either by individual point-by-point calibration of monitors at the factory (at the moment, this method successfully solves the problem of backlight unevenness on white), or by precise selection or individual adjustment of triads - both of which, of course, increase the cost of the monitor. So for now, all that remains is to carefully study the monitor screen when purchasing, in order to be able to immediately discard the unsuccessful copy.
Thirdly, and this is a problem not specific to the XL series, “stretching” the 24-bit representation to a larger range of colors slightly reduces color accuracy. The error is quite small, but it objectively exists.
Fourth, when working with a large color gamut, you need to be careful - most images are a priori designed for monitors with sRGB gamut, so without additional correction their colors will be distorted on non-sRGB monitors. Accordingly, the fundamental point is to use custom software that supports color management, as well as the presence of the correct ICC monitor profile in the system. However, in the XL-series of monitors this problem is solved perfectly: firstly, the included calibrator allows you to create such a profile yourself at any time, and secondly, the monitor supports hardware emulation of three color gamuts - two standard and one custom.
In general, the choice between Samsung SyncMaster XL20/XL24/XL30 and professional models with fluorescent backlighting (for example, produced by NEC or EIZO) is determined primarily by your needs. If you need the most accurate color rendition within the usual sRGB color gamut, the XL series will not be best choice. But if you're willing to make some sacrifices to be able to work in the AdobeRGB color gamut or even beyond, the SyncMaster XL models are worth paying close attention to.
Some buyers are also thinking about purchasing XL-series monitors for home non-professional use - fortunately, the prices for them cannot be called exorbitant: the younger model, SyncMaster XL20, now costs about 23 thousand rubles. Well, in this case, the XL series will not disappoint you: bright, rich colors, good time response, allowing you to play games without problems, as well as hardware emulation modes of standard color gamut, very useful when home use– not all non-professional software can work properly with monitors other than sRGB.
Other materials on this topic
Monitors for professionals: NEC LCD2190UX and Samsung XL20
Samsung SyncMaster XL20: troubleshooting
What is called color gamut? It defines the specific range of spectrum visible to the human eye. Because the colors that imaging devices such as digital cameras, scanners, monitors, and printers can produce vary, a specific gamut is used to match them.
Additive and subtractive types
There are 2 main types of color gamut - RGB and CMYK.
Additive gamma is created by mixing light of different frequencies. Used in displays, TVs and other devices. The name RGB is made up of the initial letters of red, green and blue light used for this generation.
Subtractive gamut is created by mixing dyes that block the reflection of light, resulting in the desired color. Used for publishing photographs, magazines and books. The abbreviation CMYK is made up of the names of the pigments (cyan, magenta, yellow and black) used in printing. The CMYK color gamut is significantly smaller than the RGB space.
Standards
Color gamut is regulated by a number of standards. Personal computers often use sRGB, Adobe RGB and NTSC standards. Their color models are depicted on the chromaticity diagram in the form of triangles. They represent peak RGB coordinates connected by straight lines. The larger the triangle area, the more shades the standard can display. For LCD monitors, this means that a product compatible with the larger model can produce a wider range of colors on screen.
sRGB
Color gamut for personal computers defined by the international standard sRGB established in 1998 by the International Electrotechnical Commission (IEC). It has taken a strong position in the Windows environment. In most cases, displays, printers, digital cameras and various applications are calibrated to reproduce the sRGB model as accurately as possible. If the devices and programs used to input and output image data are compatible with this standard, the differences between input and output data will be minimal.
Adobe RGB
The chromatic diagram shows that the range of values that can be expressed using the sRGB model is quite narrow. In particular, the standard strongly excludes rich colors. This, and the development of devices such as digital cameras and printers, has led to the widespread use of technology capable of reproducing tones that are not included in the sRGB range. In this regard, the Adobe RGB standard has attracted general attention. It is characterized by a wider color gamut, especially in the G region, that is, thanks to its ability to display brighter green tones.
The Adobe RGB standard was established in 1998 by Adobe Systems, which created the famous Photoshop series of photo retouching programs. Although it is not international (like sRGB), thanks to its high graphics market share Adobe applications V professional environment image processing, as in the printing and publishing industries, it has become such de facto. An increasing number of monitors can reproduce a large portion of the Adobe RGB color gamut.
NTSC
This analog television standard was developed by the US National Television System Committee. Although NTSC color gamut is close to Adobe RGB, its R and B values are slightly different. sRGB occupies about 72% of the NTSC range. Monitors capable of displaying the NTSC model are essential for video production, but are less important for individual users or for still image applications. sRGB compatibility and the ability to reproduce the Adobe RGB color gamut are key for displays used for photography.
Backlight technologies
In general, modern monitors used with PCs, due to the specifications for their LCD panels (and controls), have a color gamut that includes the entire sRGB space. However, given the growing demand for wider gamut reproduction, the color space of monitors has been expanded. In this case, the Adobe RGB standard is used as the target. But how does this expansion happen?
This is largely achieved thanks to improved lighting. There are 2 main approaches. One of them is to expand the color gamut of cold cathodes, which is the main backlight technology, and the other affects LED backlighting.
In the first case fast decision is to strengthen the color filter of the LCD panel, although this reduces the brightness of the screen by reducing light transmission. Increasing the brightness of the cold cathode to counteract this effect tends to shorten the life of the device and often results in illumination disturbances. The efforts of engineers to date have largely overcome these shortcomings. In many fluorescent-backlit monitors, range extension is achieved by modifying the phosphor. It also reduces cost because it allows for a wider range of colors without making major changes to the existing design.
The use of LED backlighting has begun to grow relatively recently. This allowed for higher levels of brightness and color purity to be achieved. Despite certain drawbacks, including lower image stability (due to radiant heating issues for example) and difficulty achieving white uniformity across the entire screen due to the use of a mixture of RGB LEDs, these issues have been addressed. LED lights costs more fluorescent lamps and was used less, but due to its effectiveness in expanding the color gamut of the display, the use of this technology has increased. This is also true for LCD TVs.
Ratio and Coverage
Manufacturers often indicate the area of the monitor's color gamut (that is, the triangles on the color chart). Many people have probably seen in catalogs information about the ratio of the gamma of a device to an Adobe RGB or NTSC model.
However, these figures only speak about the area. Very few products cover the entire Adobe RGB and NTSC space. For example, the Lenovo Yoga 530 color gamut is 60-70% Adobe RGB. But even if the display shows 120%, it is impossible to determine the difference in values. Since such data is prone to misinterpretation, it is important to avoid confusion with product characteristics. But how to check the color gamut of the monitor in this case?
To eliminate specification problems, some manufacturers use the term "coverage" instead of the word "area." It is obvious that, for example, an LCD monitor with a color gamut of the Adobe RGB color model at 95% can reproduce 95% of the gamut of this standard.
From the user's point of view, coverage is a more convenient and understandable characteristic than area ratio. Although this poses challenges, showing in graphs the color gamut of the monitors that will be used for color control will certainly make it easier for users to form their own judgments.
Gamma Conversion
When checking your monitor's color space, it's important to remember that a wider color gamut does not necessarily translate into high image quality. This may cause misunderstanding.
Color gamut is a characteristic used to measure the image quality of an LCD monitor, but it alone does not define it. The quality of the controls used to implement the full of possibilities display. Essentially, the ability to generate accurate tones suitable for specific needs outweighs the availability of an extended color gamut.
When evaluating a monitor, you need to determine whether it has color space conversion capabilities. It allows you to control the display gamma by specifying a target model such as Adobe RGB or sRGB. For example, by selecting sRGB mode from the menu, you can configure your monitor to have Adobe RGB gamut so that the colors displayed on the screen fall within the sRGB range.
Displays that offer color gamut conversion capabilities are both compatible with Adobe RGB and sRGB standards. This is necessary for applications that require accurate shade generation, such as photo editing and web production.
For purposes that require accurate color reproduction, in some cases the disadvantage is that a wide-gamut monitor does not have a conversion function. These displays display every tone of the 8-bit gamut in full color. As a result, the colors generated are often too bright to display in sRGB images (that is, sRGB cannot be reproduced accurately).
Converting an Adobe RGB photo to sRGB results in the loss of highly saturated color data and tonal subtleties. Thus, the pictures become faded and tone jumps appear. The Adobe RGB model can produce richer colors than sRGB. However, the actual colors displayed depend on the monitor used to view them and software environment.
Improving Image Quality
In cases where a monitor's expanded color gamut allows for a greater range of tones to be reproduced, giving more control over them and adjusting images on screens, problems such as tonal gradation disturbances, color variations caused by narrow viewing angles, and display unevenness are less noticeable in gamuts sRGB range have become more pronounced. As mentioned earlier, the very fact of having a display with an extended color scheme does not guarantee that it will provide high quality images. It is necessary to take a closer look at the various technologies for using the expanded RGB color gamut.
Increasing gradation
The key here is the built-in gamma correction function for multi-level tonal transitions. 8-bit input signals for each RGB colors, which come from the PC side, are antialiased to 10 or more bits in each monitor pixel, and then assigned to each RGB color. This improves tonal transitions and reduces color gaps, improving the gamma curve.
Viewing Angles
Large screens usually make differences easier to perceive, especially in devices with a wide color gamut, but they may have color problems. Much of the color variation due to viewing angle is determined by LCD panel technology, with the best ones showing no changes in tone even when viewed from a wide angle.
Without going into the specifics of display production, they can be divided into the following types, listed in order of increasing color change: in-plane switching (IPS), vertical alignment(VA) and twisted nematic crystals (TN). Although TN technology has advanced to the point where its viewing angle performance has improved significantly, there remains a significant gap between it and VA and IPS technologies. If color accuracy is important, VA and IPS panels are the best choices.
Uneven color and brightness
The unevenness correction function is used to reduce display unevenness related to screen color and brightness. LCD monitor with good characteristics provides low level unevenness of brightness or tone. In addition, high-performance displays are equipped with systems that measure brightness and color at every point on the screen and correct them using their own means.
Calibration
To fully realize the capabilities of a wide gamut LCD monitor and display tones according to the user's needs, it is necessary to consider the use of customization equipment. Display calibration is the process of measuring the colors on the screen using a special calibrator and reflecting the characteristics in the ICC profile (a file that defines the color characteristics of the device) used operating system. This ensures consistency in the information processed by graphics and other software and the tones generated by the LCD monitor, as well as high degree their accuracy.
Keep in mind that there are 2 types of display calibration: software and hardware.
Software adjustment is carried out using specialized software, which sets parameters such as brightness, contrast and color temperature (RGB balance) through the monitor menu and brings the image closer to the original tone using manual settings. In some cases, instead of the program, these functions are taken over by graphics drivers. Software calibration is low cost and can be used to adjust any monitor.
However, there may be variations in color accuracy due to human error. RGB gradation may suffer as a result, as display balance is achieved by increasing the number of RGB output levels using software processing. However, with software configuration achieving accurate color reproduction is easier than without it.
On the contrary, hardware calibration provides more accurate results. It requires less effort, although it can only be used with compatible LCD monitors, and does incur some costs.
In general, calibration includes the following steps:
- launching the program;
- comparison of screen color characteristics with their target values;
- direct adjustment of brightness, contrast and gamma correction of the display at the hardware level.
Another aspect of hardware setup that should not be overlooked is its simplicity. All tasks, starting with preparing the ICC profile for the correction results and recording them in the OS, are performed automatically.
Finally
If your monitor's color performance is important, you need to know how many colors it can actually represent. Manufacturers' specifications that list the number of tones are generally unhelpful and inaccurate when it comes to what the display actually displays versus what it is theoretically capable of. Therefore, consumers should be aware of the color gamut of their monitor. This will give a much better idea of its capabilities. You need to find out the monitor's gamut coverage percentage and the model on which it is calculated.
Below is a short list of common ranges for different display levels:
- The average LCD covers 70-75% of the NTSC gamut;
- professional LCD monitor with extended coverage - 80-90%;
- LCD display backlit with cold cathode lamps - 92-100%;
- LCD monitor with extended gamut and LED backlight - more than 100%.
Finally, you need to remember that these numbers are correct when the display is fully calibrated. Most monitors pass basic setup and have slight deviations in some indicators. As a result, those who need highly accurate color must correct it with the appropriate profiles and settings using a special calibration tool.
The issue of correct color display on a monitor is an eternal one. Anyone who has ever been faced with the need to print out what they see on the screen (and exactly the way they see it) knows that this is not an easy procedure. In such a situation, it is even more difficult for printers, because the quality of the “monitor - printing device” system determines the client’s satisfaction with the result and, accordingly, the success of the work and business. In addition, the idea of a remote (soft, screen - whatever you like) color proofing is in the air, which will not become a reality today or tomorrow. With the growing share of printing methods that are demanding on the quality of color processing, such as extended triad printing (more than four colors), higher demands began to be placed on monitors for professionals. Now we need a new approach to solving the problem of correspondence between colors obtained by additive and subtractive synthesis.
It is very difficult to choose a monitor from the wide range offered today. A professional monitor from a manufacturer specializing in such devices is an expensive pleasure. For most users, the difference between a household model with the eye-catching Pro prefix and a monitor designed to work with color is not obvious, especially since it is also not always clear from the characteristics. Therefore, it makes sense to understand what features professional monitors have and what conditions they must satisfy in order to meet modern requirements.
Increased color gamut
Most TFT monitors can reproduce up to 75% of the NTSC color space. But while this color gamut is theoretically large enough to include print synthesis colors, its size and position in color space is such that these monitors are not suitable for reproducing print colors on screen. The reason lies again in the fundamentally different color models of monitors (RGB) and printing devices (CMYK). To include all printed colors, the color gamut of RGB devices (in this case monitors) must be significantly expanded.
Most The best way increasing the color gamut of a TFT monitor means optimizing the spectral characteristics of the backlight. By combining the achievements of colorimetric and chemical technologies, it became possible to create a phosphor with a modified spectral characteristic and better reproduction performance in the red and green regions of the color gamut.
The results of these changes are clearly visible in the illustration: the green and red regions of the spectrum have shifted, resulting in an increase in the size of the color gamut. Much brighter greens and reds became available.
Color gamut optimization
Unfortunately, only expanding the color gamut does not allow you to capture all the colors reproduced by devices with subtractive synthesis (or, more simply, CMYK devices). The main goal was and is to achieve the most complete color match between the colors on the monitor and the print. The simple example shown in the figure demonstrates that if the color gamut of one monitor (black line) is larger than that of another (red line), this does not mean that it will reproduce the colors of printing devices better (white line).
In addition, you need to clearly understand the difference between the size of the color gamut, that is, the position of the extreme points on the graph, and the quality of the color gamut - the actual correspondence of the colors on the monitor to the printing device.
This means that a monitor with a smaller but optimized color gamut may be more suitable choice for color correction or remote proofing than a solution with a nominally larger coverage but relatively acceptable color rendering.
Let's talk about spaces
Today in color management systems there are two main RGB working spaces, very close to each other - Adobe-RGB and ECI-RGB.
Adobe-RGB system - good decision for most tasks, which, unfortunately, is not well suited for transmitting the colors of printing devices and organizing screen proofing. The reason for this is that it uses a white point of 6500K and a gamma of 2.2. Let us recall that the standard for color management in printing is considered to be a white point of 5000 K, and gamma 2.2 does not correspond to the classic dot gain curve offset printing. Additionally, the Adobe-RGB color gamut virtually cuts off the rich blue colors produced by offset printing.
ECI-RGB is a much better option. It was created taking into account all standardized printing methods, it excludes colors that cannot be reproduced in the RGB system, and finally, ECI-RGB uses a white point with a color temperature of 5000 K and a gamma of 1.8. That is, it better complies with generally accepted printing conditions and print control. This space is an excellent basis for a hardware independent system: it includes most RGB devices and complies with print standards. To be clear, ECI-RGB cannot reproduce the very rich blue colors that sRGB (and Adobe-RGB) can produce, but these colors also cannot be reproduced on any printing device.
If we take as an example working with photographic images, where Adobe-RGB dominates, we can note several interesting moments. On the one hand, Adobe-RGB is the standard working space of professional digital cameras and pre-installed system in the main tool of photo artists - Adobe Photoshop. On the other hand, the ICC standard uses the D50 white point, and the vast majority of viewing stations and flash units also use a color temperature of 5000 K as the white point. The photograph itself is just the beginning of the process, most photographs are eventually printed, and the printing process is again better suited to a white point of 5000K and a gamma of 1.8. Therefore, using the appropriate color space - ECI-RGB - will help get the highest quality results and eliminate typical problems, especially since most RAW converter programs support the ECI-RGB space as standard. Remarkably, no photo printer (including dedicated 12-color models) can reproduce all Adobe-RGB colors, although this system, as we saw earlier, cuts off the blue tones available to these devices. It turns out that in this situation ECI-RGB again offers better coverage of the color space of the printing system.
Difference between "calibration" and calibration
The accuracy of the monitor's calibration and profiling directly determines the accuracy of the display of colors included in its color gamut, and the imitation of colors that go beyond its gamut. There are many devices on the market designed to calibrate monitors, and while some of them are very powerful and accurate, the quality of the results depends on the ability to control the monitor itself. The most common case is when it is not the monitor itself that is calibrated, but with the help of a measuring device - a colorimeter or spectrophotometer - changes are made to the color matching table of the video card. In this case, the created profile is forced to make too many changes, which negatively affects color rendition. For example, if the starting white point of a monitor is 7000 K, and the gamma is 2.2, then bringing such a monitor to meet printing requirements (reducing the white point by 2000 K and the gamma by 0.4) will cause a loss of up to 40 gradations per channel. This will be noticeable when working with a monitor, and such a device cannot be recommended for use for professional color work. If your monitor has the ability to change brightness according to color channels, then usually the range of changes is limited to one hundred steps, and this is not enough for accurate installation. Something will be compensated by the profile, but the inability to adjust the monitor gamma will result in a loss of up to 19 gradations per channel when recalculated. If gamma adjustment is available, it is only for 50% gray. For better results, a color-oriented monitor must have preset gamma values that comply with the standard. But the optimal option is the possibility of hardware calibration of the color matching table (Look-Up Table, LUT) of the monitor itself while preserving the original LUT values graphics adapter. Professional monitors with the possibility of hardware calibration offer adjustment of the internal LUT with an accuracy of up to 14 bits, that is, they have not 256 gradations, like a regular monitor, but 16,384, which practically eliminates color rendering inaccuracy.
How can you prove it?
The monitor is calibrated, the system is configured, all profiles are connected, but the client is still dissatisfied or not sure that everything is really correct. A way out, other than proper organization of viewing conditions (correct ambient light, no bright or dark spots in the field of view, etc., etc., which the reader probably knows very well), may be to certify the monitor according to a generally accepted standard, for example UGRA. Some professional solutions allow you to do this. The basis of this operation is the measurement of gray balance in everything dynamic range and a set of colors, in this case from the UGRA/FOGRA Media Wedge set. The result indicating the maximum color deviation and average deviation can be saved in PDF format and ensure its accuracy. This may be an additional argument in favor of choosing the services of a printing house or prepress department that offers such a service.
Unfortunately, the length of the article does not allow us to discuss many more interesting issues relating to color rendering in general and monitors as tools for working with color in particular. The current state of printing and market trends place new demands on all aspects of production. A professional monitor today is not just a device, but rather an approach to solving a problem. The development of such a monitor is backed by many years of experience and serious research, which distinguishes it from mass products. Of course, the price of the device is sometimes a determining factor, but everything here is not as gloomy as many people think. The onslaught of new developers is already leading to solutions high level inevitably become cheaper, and more and more models appear in more affordable configurations without sacrificing functionality. This positive trend is another argument in favor of purchasing a professional monitor, adapted for printing tasks, which will allow you to see the color on the screen as it should be.
Supports hardware calibration with recording of a 12-bit LUT into the monitor memory and has an expanded color gamut. In this case, the video card operates at its 8 bits/color and no color loss should occur. So I turned on the wide color gamut instead of the factory setting to sRGB and the monitor was calibrated using the native program. But I didn’t rejoice for long - for some reason the photos that looked great in the editor were red-green when viewed in the browser and in the system...
Color gamut measurement result in (about CIE 1931):
The triangle filled with colors is the measured actual color gamut of the monitor after calibration, blue - sRGB, yellow - AdobeRGB. As can be seen from the figure, in the area of green and red colors there is a clear overlap of the standard sRGB space for WEB.
What follows from this? Some problems follow from this:
- if extended color gamut is enabled (the monitor does not have sRGB mode enabled), and image viewers do not know how to take into account color profiles, then the screen will be garbage; in my case, photos that looked great in the editor were red when viewed in the browser and in the system. green, which made me start digging into this issue further.
- if viewers know how to take profiles into account, but the image itself does not contain information about the file’s profile, then again it will be garbage.
For example, displaying a bright green RGB pixel (0,255,0) without taking into account the color gamut on a regular sRGB monitor and on a monitor with extended gamut will produce completely different actual colors on the screen. On a monitor with a wide color gamut, this pixel will be much greener. For example, you can evaluate the actual discrepancy of the green color in the picture (the upper corner of the triangle).
For example, the differences may be as follows (at the top is MS Paint without profile support, at the bottom is FireFox with profile support enabled):
.png)
This problem is even more noticeable on the Internet because:
- rare images on websites contain a mention of color space,
- Of the common browsers, only FireFox 3 supports color management, and only after configuration (IE, Opera - unfortunately, no).
There are few options for the development of events - either reset and return the monitor to sRGB mode, or deal with the software. I decided to take the second path and now after Opera I’m gradually getting used to FireFox, which, by the way, can be configured in two ways:
- download the plugin with the obvious name Color Management
- go to about:config and change the gfx.color_management.enabled parameter to TRUE. To use a color profile recorded in the system, you don’t need to do anything else, although you can specify the path to your monitor’s profile in the gfx.color_management.display_profile parameter.
As a viewer, I have been using FastPictureViewer for a long time, which has a convenient primitivism interface, high speed and quality. As it turned out, he works completely calmly with color profiles. But Microsoft products that come with Windows (standard viewers, Paint, etc.) for some reason cannot work with color.
Loading...
