Layers are currently the most powerful tool for working with photographic images. When you edit a photo, whether in Photoshop or Paint Shop Pro, you can't do without multiple layers of the image. Sometimes more complex layers are used - custom layers, effects and masks based on layers. Layers are everywhere. And the question involuntarily arises: how did users manage without them before?

The answer is simple - using channels. You can easily spot a Photoshop veteran by the fact that he uses the Channels palette as often as the Layers palette. But this should not be regarded as old-fashioned. Rather, this is evidence of professionalism, since the use of channels opens up wide opportunities.

So, what is a "channel". The standard definition - "a two-dimensional array of information, usually 8-bit" - is unlikely to clarify the situation. Therefore, let's take a closer look at the two main types of channels - color information and alpha channel - from the point of view of their practical application.

Color channels

The easiest way to see color channels in action is to use Photoshop's Channels panel. Open a regular 24-bit RGB photographic image. In the channel palette you will see 4 layers, each with its own icon: RGB, Red, Green and Blue. If you click on RGB, you will see the image that you usually see - composite and full color. For each of the other channels, a grayscale version of it is displayed. The keyboard shortcuts Ctrl+1, 2, 3 allow you to view each of the color channels separately, and Ctrl+~ - a regular composite image.

The full spectrum of RGB colors is created from the red, green, and blue color channels, where they are represented in a gray scale.

To understand what information is displayed in the Layers palette, it is worth observing the channels when working with a test image of a rainbow gradient (in other words, an image of all the colors of the rainbow). In a grayscale image that represents a channel, each of the pixels can represent one of 256 values. You will see that the red part of the rainbow when viewed in the red channel will be white. The yellow stripe of the rainbow will be white in the red and green channels, but will be black, i.e. absent, in blue. In fact, the rainbow image shows that the full spectrum of 16 million colors can be obtained by combining values ​​from 0 to 255 for red, green and blue (256 x 256 x 256). In our image, the yellow stripe corresponds to large values ​​of the red and green channels and 0 to the blue channel. Photoshop works with an image not by individual pixels, but by channels. In this case, three eight-bit layers - red, green, blue - are superimposed, and we get the final image.

Of course, not all images are created in RGB, but this is not a problem since the channels are very easy to customize for different needs. We can convert our image to a different mode using the Image > Mode command. For Bitmap and Grayscale there is only one channel, which represents 256 values ​​from black to white. In Lab mode there are three channels: A (color value between green and red), B (between blue and yellow) and L (luminance value). Separating color from its brightness can be very useful. Select the luminance channel and convert it to a grayscale image. The result will be much better than if you converted the scanned RGB image.

The Lab color model can be very useful. But still the most important, after RGB, is CMYK. This model is print oriented. Convert the rainbow image to CMYK. The first thing that catches your eye is the sudden change in some colors. The fact is that CMYK does not support many pure RGB colors. The second difference is that four color channels have appeared: Cyan, Magenta, Yellow, Black (turquoise, purple, yellow, black). Look at the yellow stripe of the rainbow in the yellow channel - you will see that it is represented by black.

In the CMYK palette, the channels represent the ink colors used in multi-layer, four-color printing.

This mode differs significantly from RGB because Photoshop has to work with ink colors that combine with each other in a subtractive manner (summing all the colors together results in black). In RGB, on the contrary, the principle of addition is applied, and the superposition of all colors will produce white. But, by and large, all color models are similar to each other. And Photoshop can recreate the full gamut of any of them with no more than four eight-bit channels, each of which has no more than 256 values ​​(or 65,536 values ​​if you really want to and go to Image > Mode and choose a 16-bit channel).

Channels are the primary tool for working with color, so it's worth looking at the Channels panel occasionally to learn how Photoshop creates different colors. This is especially true when working with a CMYK model that is designed for printing. When working with RGB, what you see on the monitor does not always correspond to what will come out when printed. Although the values ​​of each channel reflect this. Moreover, if you want to replicate an image, you need to consider factors such as dot blurring and gray component replacement. This means that accuracy in working with color channels is very important, since color separation subsequently depends on it.

Channels are useful for more than just CMYK printing. You will find their use in RGB as well. Let's say you can edit not the entire image, but a separate channel. When adjusting color, it is worth looking at individual channels to identify defects in the scanned image. For example, if you find a blurred or misaligned area in the red channel, you can correct this issue by using a sharpening filter or adjusting the levels.

And in order to create some special effect, you can apply an artistic filter to one of the channels. In any case, you can immediately see the result of your actions on the composite image - just make the RGB channel visible. Just remember to select the desired color channel again later if you continue to work on it.

The channel merging function provides ample opportunities. For example, using the Apply Image command, you can overlay information from any channel of another image of the same dimensions onto the RGB channel of our image and customize this effect by changing the opacity and color mixing mode. The Calculation command allows you to select two layers and create a new layer, selection, or document. If you use the subtractive color mixing mode, you will select areas of the image that have changed compared to the original.

With the introduction of the Channel Mixer command and custom layers in Photoshop 5, the ability to combine channels has expanded. The channel mixer feature is used only for individual images and allows you to customize each channel by adding information from other channels. With its help, you can create special effects, swap channels, and correct color defects in scanned images. It's also ideal for creating "tinted" and high-quality halftone images (and you can control how each color channel is converted to grayscale).

Channel blending is very helpful when converting color images to grayscale.

Adjusting colors using channels will undoubtedly come in handy. But the most common way to use them is to work with secretions. Often, image elements are much clearer in a single channel than in a composite image. For example, selecting a bear in the bear.psd training file is much easier in the blue channel.

Alpha channels

Once you've created a selection, you'll probably want to save it. This can be done in the alpha channel. To do this, use the “Selection > Save Selection” command or the “Save Selection as Channel” icon in the Channels panel. After this, a new channel appears in which the selected pixels are displayed in white, the unselected ones in black, and the blurred pixels at the border of the selection in shades of gray.

By double-clicking on the channel icon, you can rename it and set the color it will appear in the composite image. You can work with the alpha channel like any other, for example, adjust levels or apply filters. Moreover, you can edit this channel using a brush - for example, paint over defects. When you are satisfied with the result, use it. To do this, convert the alpha channel into a selection using the Selection>Load Selection command, the Load Channel as Selection icon in the Channels panel, or simply by Ctrl-clicking on the channel icon. If you have multiple alpha channels, you can create more complex selections. For example, you have selected and converted an image of a person and bushes in the background to alpha channels. You can select only the bushes if you select them and load the channel as a selection using the "subtract" option. Keyboard shortcuts will speed up this procedure: click on the icon while holding Shift+Ctrl - this will add a new area to the selection, Alt+Ctrl+click - subtract from the selection, Alt+Shift+Ctrl+click - will give the intersection of two selections.

Alpha channels can be saved and loaded as selections.

Once you've converted the alpha channel to a selection, it will immediately appear on screen and you can transform it, copy it to a new layer, or edit it in any way. Shimmering dotted line along the edge of the selection does not very accurately indicate its boundaries - you need to take this into account. It only displays alpha channel pixels that have gray intensity below 50%. For most selections this makes little practical difference. But the advantage of the alpha channel is that it allows you to work with 256 levels and thus create complex, variable transparency masks.

How can you use these masks? Here are some examples (it's actually easier to do than it looks when you read it). Click on the "Create New Channel" icon and create an empty alpha channel, then apply a gradient to it and select the composite channel again. Ctrl-click on the alpha channel icon. Now apply any artistic filter to the created selection. Its effect will depend on the halftone values ​​of the gradient mask. It will seem that the photograph is gradually turning, for example, into a painting.

The alpha channel can be used as a variable opacity mask.

Another example: create a copy of the alpha channel from a text selection and apply a Gaussian blur to it. After that, subtract the original channel (Alt+Ctrl+click) and you will get a new channel that will show only the noise surrounding the text. Now select this area in the composite or any of the color channels. You can adjust the levels so that the selection glows, or even remove the original text and the glow appears to be part of the photo.

You have the foundation, now experiment - you can create many effects using shadows, extrusions, vignettes, etc. Surely, if you get serious about this, you will need the ability to save alpha channels with your file. But Photoshop's capabilities in this regard are surprisingly limited - the program supports saving the alpha channel in a tiff file or in Photoshop itself (but the number of channels in a file, including color ones, is limited to 24). This won't pose a problem if you only work in Photoshop. But the presence of an alpha channel can significantly affect the export of the file to one of standard formats. For example, when saving for the Web, in the dialog box that appears, you can use the alpha channel as a mask to adjust the quality and, accordingly, the size of jpg and gif files. Using the alpha channel, you can draw attention to a certain part of the image that will be of the highest quality. The quality of other areas of the image will deteriorate, but this will significantly reduce the overall file size. Alpha channels are also useful when working with transparency. Create an alpha channel that covers the area that you don't want to be visible in the web version, and Ctrl-click to select that area. Now call the Transparent Image Export Wizard and select gif. The selected area will become transparent in the final file, and you will be able to avoid making irreversible changes to the original. The wizard allows you to export the image to a png file that supports 24-bit color and 8-bit transparency. If you create an alpha channel with a radial gradient, you will get a vignette. Unfortunately, few programs support 32-bit png files with transparency. The only exception is, perhaps, Director 8.5.

With the ability to add spot colors in CMYK, alpha channels are also useful for high-quality printing. Select the area of ​​the image that you want to print as a color fill, and then use the New Spot color command from the Channels panel menu. When you set a color, click "Custom" and select a color, for example from the Pantone library.

Please note that adding a color fill is not as simple as it seems. The image on the screen, as you know, does not always correspond to what is printed. Ink colors often cannot be represented in RGB and Photoshop simply shows what it thinks the image should look like when printed layer-by-layer. If you save your file in DCS 2.0 format and load the EPS composite image into a professional publishing program, you can color separate the four primary colors and custom color files you created.

The custom color channel allows you to display ink colors that are not included in the CMYK palette.

There's no doubt that channels play a very important role in photo editing, from adjusting colors and highlights to working with images for the web and high-quality prints. But time moves on, and layers often produce better results than channels. Having created a selection, copy it to a separate layer - and you can work with it independently, and, if necessary, return to the original version. The same goes for many other effects that were previously created using channels. Today, custom layers, effects, and layer-based masks do a better job of accomplishing this task.

The canal system was also improved. So, although in many areas channels are gradually being forced out of use, they are unlikely to disappear completely. If only for the simple reason that layers are created based on channels. Strictly speaking, a layer is a set of independent color information channels and alpha channels, one of which controls transparency, and the second acts as a layer mask. The same goes for custom layers, which are essentially alpha channels through which color is adjusted.

Photoshop, like any other photo editor, creates an image on the screen by processing values ​​from the color and transparency channels of the layer. And so, one by one, all the layers from the background to the foreground. Of course, in reality, working with an image is much more complicated - the program calculates color mixing modes, opacity, settings, etc. But it's based on a step-by-step mathematical process. The program does not see the image; it works with the data array of each channel. Any photo editor “thinks” in terms of channel categories. This is a habit worth adopting as a professional user.

I recently read a translation of an article using channels in Photoshop on a “famous” site. The article emphasized that Photoshop does not distinguish between colors and sees all images in black and white gradations. Photoshop shows color images because we “expect” to see them in color, and it quietly adds some numbers that make the magic happen. It is not clear what the logic of such reflections is based on. Either because old versions of Photoshop showed the channels as black and white prints, or because of something else. It’s not surprising that questions in the comments in the style of “wow, so it turns out that from a black and white photo you can make a color one?”

For that matter, Photoshop doesn’t see anything at all. Photoshop is simply a program written by a person in a programming language. Photoshop does not see gray, white, red or green. Photoshop navigates graphics like Neo in the Matrix. He sees pixels as a collection of zeros and ones, and makes decisions based on digital parameters. Photoshop does nothing more than change digital values, the values ​​are converted into colors that the human eye can recognize. Other animals' eyes are structured differently, and they apparently need some other Photoshop, but it hasn't worked out yet.

It is also unclear where, finally, our domestic accessible and understandable articles about Photoshop, color, printing are, where our Dan Margulies are. The entire RuNet translates Western designers and graphics teachers. It seems that we have had design itself and good designers for a long time, and the only famous writer on the RuNet so far is Artemy Lebedev, and even then, he writes about something of his own. In this article I will try to address the issue of channels, going through the basics of the appearance of light and color along the way. We will go through the entire logic of the appearance of colors on the screen from beginning to end, and I assure you that by the end you will understand the essence of channels in Photoshop no worse than Dan Margulis. I'll start with the basics and tell you how color comes about in the first place. What is the difference between light and color. This is very important for a correct understanding of the channels. Moreover, I will try to cover not only RGB channels, but also channels in CMYK and LAB.

Photoshop color space and channels

Let's agree right away: channels and color space are not the same thing. If we're talking about channels, then we're talking about channels. And not about RGB channels or CMYK channels. What is color space in Photoshop? Color space is the essence, the formula by which Photoshop assembles an image. The channels directly depend on the color space in which Photoshop works. If the color space is RGB, then these are 3 RGB channels, if the color space is CMYK, then these are other channels, channels for the CMYK color space. But there are many color spaces, and each has its own channels! It turns out the topic is bottomless? Margulis only scribbles ABC books one after another in the Lab space, but we just have an article. It's not that scary. Once you understand how the channels of one color space are arranged, you can easily understand the others. Therefore, we will start with RGB channels, but first let’s get started with the theory.

Color space in Photoshop switches to Image > Mode. If you go to this menu, you will see a series of color spaces in which Photoshop can work. This Bitmap, Grayscale, Duotone, Indexed Color, RGB, CMYK, Lab and Multichannel. Accordingly, each of these modes has its own channels, arranged in its own way. The channels themselves for any image can be viewed in the channels panel Windows > Channel. By opening this panel you will see the channels themselves and their final result. In some color spaces you will only find one channel. Others, such as CMYK, have four channels. If filters do not work for you, selection areas are not copied, some colors are not included, graphics are not imported from one window to another - urgently check the color mode. Most likely, the image does not have a typical color mode, such as CMYK or Indexed Color.

I'll say even more. If you opened black white image, it is very possible that its color mode is Grayscale, if you opened a GIF banner saved from the Internet, its color mode is Indexed Color, since GIF format saved only in this mode. If you have a large TIFF file on hand, check the mode, most likely it is CMYK, since TIFFs are usually saved for printing in offset, and the color mode for printing in offset is CMYK. And only one color mode always wins. All filters work in it, colors are displayed, graphics are copied. This color mode is truly the king of modes, since Photoshop itself is designed to work with it. And the name of this mode is RGB. And most images, photographs and other graphics you'll work with will have this color mode. And that's why.

Monitors and RGB

RGB (Red- red, Green- green, Blue- blue) is the most common color model because any modern on-screen luminous devices are based on the RGB color model. Yes, Photoshop can simulate any color space, from CMYK to Lab, but ultimately what we see on the screen is converted to RGB in any case. We work in Photoshop, on the agenda is a printed TIFF file, CMYK color space, in the Chanel channels panel there are four paint channels. But when displaying the work area, the monitor converts them to RGB. Why?

This is how monitors are designed, and this is how almost all luminous screen devices are designed. And then you will understand why. Ultimately, it all comes down to the monitor’s ability to reproduce some colors in principle. In its hardware capabilities, in the quality of its matrix and coverage color range. Whatever color space we choose to work in Photoshop, the monitor displays it using RGB. The monitor displays colors as best it can, as well and brightly as the quality of its matrix. So we all end up with our piece of hardware on the table in the end. You can work with excellent color profiles, in flexible color spaces with a wide color gamut, but all is useless if the monitor is bad.

Light and color

To reverse Locke's sayings, there is light and there is color. And light has color. This topic is not the subject of our article, but is necessary for a correct understanding of channels in Photoshop. And especially RGB and CMYK channels. What is light? Light is part of electromagnetic radiation. This is a natural phenomenon that ranks with other electromagnetic radiation such as infrared rays, x-rays, microwaves and ultraviolet radiation. All of them (electromagnetic radiation) are measured in nanometers (nm). Light is measured at 400-700 nm, and I think you can already guess why. Why in the radius from 400 to 700. Is it different? Exactly. And its difference is determined by its color.

Light rays of different colors are measured in different numbers of nanometers, with violet measuring 400 nm, green 550 nm, and red 700 nm. When refracted in a prism, light is split into its component colors: red, orange, green, blue, indigo and violet. Every schoolchild knows this from physics lessons. And based on all that has been said, we can draw simple conclusions that will help us understand the RGB channels:

• white “light” is the combination of all colors of the spectrum
• black “light” is the absence of light at all.
• gradually adding all the colors of the spectrum to each other “brightens” the light until it becomes white
• the gradual removal of parts of the spectrum “darkens” the light until there is no light left at all.

Surface color

The color of the surface is arranged differently, but is tied to light. We see the color of objects because objects reflect the light falling on them. Different surfaces have different reflective abilities. If a certain surface does not reflect light at all, but absorbs all the rays of the spectrum, then we see black. What else can you see if the object does not reflect light? If the surface reflects all the rays of the spectrum, we see white color. For example, paper reflects all the rays of the spectrum and we see it as white. The moon is white because it reflects the light of the sun, and not because it itself glows purely Samsung Led TV.

Further more. If, for example, a certain surface absorbs all the rays of the spectrum except blue, then this surface looks blue, since it reflects only the blue part of the spectrum. If an object reflects only one part of the spectrum, for example red, then we see it as red. If it reflects the devil and absorbs the devil, then we see the devil. For example, a surface may reflect a little yellow, a little blue, a little green, and absorb everything else. All other, “non-pure” colors consist of this confusion. They are formed by mixing reflected rays of the spectrum. Perhaps this is enough for the theory of color and light. Let's move on to the channels themselves in Photoshop.

Channels in Photoshop for RGB

From pure theory, let's move on to channels in Photoshop. When creating monitors, smart people did not reinvent the wheel. The monitor emits light. The developers took advantage of what Mother Nature offered us and created RGB. How is it built? It consists of 3 channels: red (Red), green (Green) and blue (Blue). When superimposed on each other, the 3 original colors create the composite colors: magenta, cyan and yellow. Together, we get the usual rainbow or spectrum.

The three RGB channels act on each other in the same way that the rays of a spectrum act on each other. When superimposed on each other, a white color is achieved. If all channels are missing, it turns out black, which is logical. Either light or darkness. If one of the channels is missing, one of the composite colors (magenta, cyan or yellow) is obtained. Each RGB channel has a value scale from 0 to 255, where 0 is no light and 255 is the maximum possible light. In our case, this is not white light, but the light of one of the channels, blue, green or red. When all three channels are crossed, taking into account the fact that each channel can have a color gradation, from black to the lightest possible, the entire multi-million color palette in RGB is obtained.

I thought for a long time about how best to depict the overlay of color channels on top of each other, but in such a way as to take into account the gradation of each channel to black, that is, to the absence of light. After some unsuccessful experiments, I depicted them in the form of a flower. And although this flower does not show all possible shades RGB colors, it shows quite well how RGB mixes channels.

RGB channels as a mask option in Photoshop

So what do we know about channels? Already quite a lot. We know that there are three channels in the RGB color space, blue, red and green. We know that when superimposed on each other, composite colors are formed and that each channel has a lightness and darkness parameter from 0 to 255. It's time to look at how an image is generated in RGB.

I open Photoshop, select a beautiful photo and turn on the channels. If you don't know where they are, open Windows > Channels. I will also use the panel Info And Color. They can also be found in the menu Windows. By turning on the channel panel, you will probably see the following picture: one color image, and 3 separate channels with black and white masks, which indicate the degree of illumination of each specific area of ​​​​the photo by a specific channel. If an area in the image is black, then this channel is completely absorbed by the surface; if it is light, it is completely reflected; if it is gray, it is partially absorbed and partially reflected.

You may also see a different picture, color channels instead of black and white. This means absolutely nothing, and does not at all indicate that Photoshop sees everything in color, black and white, or brown-crimson. Photoshop is just a program, it doesn't see anything. It sees the channel values ​​for each pixel and composes the image. Accordingly, the more colorful the photo, the more it weighs, since there is a lot of information on the color of each pixel, and the more uniform it is, the more single-color pixels, the less the photo weighs. Because the information on some pixels is repeated. Black and white photographs weigh significantly less than color ones, and a white sheet, compared to a photograph of the same size, weighs nothing at all.

Whether your channels in Photoshop are color or black and white depends solely on the version of Photoshop and the settings installed. If you see black and white channels, go to Edit > Preferences > Interface and check the box Show Chanels in Color. It doesn't make any difference. For color channels, the black area on a particular channel is the zero color intensity value, and the brightest (for example, red, on the red channel) is the maximum channel intensity value of 255. That's all. And also in black and white version. Black - 0 value, white - 255.

In this sense, each channel is a kind of mask, where the black area covers the image, the white area shows, and the gray area half-shows.

Let's consider the operation of channels with black and white images in RGB. For our experiments we will need palettes Color, Channels, Info And Color Picker. Open Color Picker and choose a pure gray color. It is impossible not to notice that in a gray color without tint, the channel values ​​are equal to each other. Which is natural, because if R0 G0 B0 creates a black color (see, the absence of light reflection from the surface), and R255 G255 B255 creates a white color (see, a combination of the entire spectrum, a school prism), then it is logical that with a gradual increase in the values ​​of each channel with an equal value will result in a pure gray color without a hint of tint.

Let's do a little experiment. I opened the photo and using Image > Ajustiments > Desaturate converted it to black and white.

Now I have chosen the tool Color Sampler from the Tools panel and made 4 color proofs in different places of the photo. To display the digital values ​​of the channels, I will open the Info panel. We see that in all 4 cases the channel values ​​are equal to each other. Let's complicate the task.

I'll go back to the color correction menu and apply the tint filter. Image > Adjustments > Photo Filter In the Filter panel, I'll select the solid blue color R0 G0 B255 and tone the photo slightly.

As you can see, the hue of the photo has changed, although it is still perceived as B&W. Let's look at our color swatches in the Info panel. The red and green channel values ​​remain unchanged. And the value of the blue channel exceeded the values ​​of the red and green. Due to this, the black and white photograph received its bluish tint, because the intensity of the blue channel exceeds the other two. I achieved clean results by using a pure blue R0 G0 B255 with zero values ​​for the red and green channels when color grading. If I had used a shade that was not entirely pure, for example R10 G15 B250, then my values ​​would not have been even. In this case, the filter would also affect the Red and Green channels, but the photo would still get its blue tint, since the value of the blue channel would be a hundred times higher than the others.

Channels in Photoshop and sepia

How is the Sepia effect created? The photo is still black and white. It just has a yellowish tint. How does RGB create the color yellow? Known as when superimposing Red on Green. That is, R255 G255 B0

Open a black and white photo Apply the effect Image > Adjustments > Photo Filter, but this time we will use the pure yellow color R255 G255 B0. It's not hard to guess what we'll get in the Info panel.

The values ​​of the Red and Green channels increased evenly, while the values ​​of the Blue channel remained unchanged. Due to this, the photo received a yellowish tint. Now that you understand the nature of RGB channels, let's look at a color image.

Channels in Photoshop and color image

With a black and white image everything is simple. In each area of ​​the image, all channels are equal to each other. The values ​​are of course different due to the degree of lightness and darkness, but all three channels are always synchronous with each other. With color images everything is different. Each pixel in a color image contains different information on all three channels. That's why it's colored. Due to this, a color image weighs more than a black and white image. Let's look at our photo.

The conditions are the same. Already a color photograph, the previous 4 color samples. 1) In the sky, 2) on the clouds, 3) on the dark part of the clouds and 4) on the tree. Let's see what's happening in the sky. In a section of the sky, the channel values ​​are 0 in the red channel, 56 in the green channel and 134 in the blue channel. The red channel is missing and we do not see it. 134 blue gives a pure dark blue color. And 56 of the green channel adds brightness towards the blue. As you remember, R0 G255 B255 give a bright blue color. The result is a blue sky, where the blue channel creates a dark blue tone, and the green lightens it towards blue.

The second value is the light part of the cloud. In the Info panel the values ​​are 240 for red, 243 for green and 247 for blue. The first thing that catches your eye is that the values ​​are extremely equal. This means the color will be close to grayscale. In our case, the values ​​are not only equal, but also high. From 240 to 247. Almost a maximum of 255, which indicates that the color will be almost white. And so it is. The clouds are extremely white. Now let's look at the shade. The values ​​are almost equal, but not completely. Blue channel 247 is higher than red, by 7 points. The green channel is also higher by 3 points. As you remember, 255 Green and 255 Blue give blue. This means the color will have a slightly bluish tint. And so it is.

In the third area, I selected the shadowed part of the cloud. First of all, we see that the values ​​are also high. 166 on red, 182 on green, 208 on blue. The values ​​indicate that this color is also quite light. But not as light as in the second sample. Light gray, and higher blue and green channel values ​​give light gray a distinct blue tint.

On the tree section, the values ​​are 3 for red, 23 for green, 16 for blue channels. The values ​​tend to zero, which indicates that the color is almost black. And so it is, the tree is really dark. As usual, the red channel is minimal; the green and blue channels win throughout the photo. Except, of course, grass, but more on that later. In this area, the green channel is significantly higher than the blue one, and accordingly the tree receives a dark greenish tone.

And a few more examples. I made two final marks on the light and dark parts of the grass. In this case, the blue channel plays. Its value is low. Red and green win. As you remember, the red and green channels give pure yellow. In our case, the red channel is not enough to switch the green channel to yellow, so the color goes towards the yellow-green swamp. But the green channel is not at its full maximum capabilities, if its value were inferior to the red one, the grass would have a reddish tint, but the green channel is stronger, and the grass is greenish. The blue channel also adds a slight tone, although it is almost imperceptible.

In our latest battle, the green channel is the clear winner. Its value is 137, half power, so the color is not bright but quite dark. The red channel tries to shift the hue towards orange, but to no avail. The blue channel is practically disabled.

And so each color section is added using RGB channels. The essence of the channel is a light intensity mask for each area of ​​the image. In the sky area, the red channel is black, which means the color consists of green and blue channels. There is no blue channel in the grass area. Green looks brighter than red, which means the grass will be mostly green. I hope you get the idea.

Reading channels by mask

This is what I want to achieve from you. I want you to understand that the channel image is a mask, where dark places mean the absence of the channel's action, and light places mean the effect of the channel's tone. Take our image as an example. You can understand the color of a photograph without seeing the colors. It can be read based on the channel masks. Now we will learn how to do this by deciphering the logic of color mixing in RGB.

The photo shows the sky, a tree, and a field. Let's see what the channels show. On the red channel the sky is completely black. This means that there is no effect of red in this area. The blue and green channels remain. On the blue channel, the color of the sky is clearly lighter, which means the action of the blue channel is higher here. But the green channel also makes its contribution. As you remember, the blue and green channels give blue. We get a light blue sky, darker towards the upper right corner, since the effect of green is noticeably weakened there.

Let's consider the field. The blue channel in this area is almost black. The brightest area is near the red channel, which is rivaled only by the green channel. Which means the field yellow color. Gradations on the green value move the color towards orange and dark red.

Let's look at the tree. On all masks its color is almost the same. This means the tree is quite colorless, close to gray. But still, on the red channel the tree is much lighter, and on the blue channel, it is darker. This indicates that the shade of the wood is red. In our case, the red is so strong that it reduced the gray to brown.

RGB and Screen mode

We can simulate RGB channel mixing ourselves. This is how I created most of the illustrations for this article. Draw ellipses on different layers, fill them with pure colors. Pure blue R0 G0 B255, pure green R0 G255 B0 and pure red R255 G0 B0. In the Windows Layers panel > Layers, change the layers' blending modes to Screen. The Screen blend mode cuts out dark pixels, favoring light pixels. But it also mixes different pixel tones in the same way it mixes their RGB color model.

I tried to write as concisely as possible, but the article turned out to be too lengthy. But now you fully understand how RGB channels are arranged in Photoshop, and not only in Photoshop. They are arranged the same everywhere, believe me. I will develop the topic of channels in my next articles on this topic. In the following parts I will describe the channels in CMYK and Lab, and also move on to their practical use in color correction and printing.

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To look inside a channel, you need to open its palette in Photoshop. It looks and works the same as the Layers palette and is located in the same panel as Layers, but in a tab to the right (if you don't see it, select the menu command Window => Channels).

Similar to how layers work, when you click once to select a channel, Photoshop highlights it, showing you that it is selected. All operations performed from this moment on will affect only it.

If you need to select several of them, click on each of them while holding down the Shift key. You can use this trick to, say, sharpen two at the same time. To turn display on or off, click on the visibility icon to the left of the name (however, you cannot turn them all off; at least one must be visible all the time).

There are several types:

1. Composite. Technically this is not really a channel, it is provided for viewing convenience only. When you use a mode that contains multiple colors (such as RGB, CMYK, and Lab), it shows everything at once, revealing the image in all its full-color glory.

Its name always depends on what mode you are working in. In mode RGB, for example, it will be called RGB. But no matter what Photoshop calls it, composite is always at the top of the palette.

2. Color. As stated above, if you are working in RGB mode, then this is red, green and blue. In mode CMYK these are cyan, magenta, yellow and black. In Lab mode (we'll look at it in future articles) these are Brightness, a and b. In all other picture modes, you will only find one, named the same as the mode you are in.

3. Alpha channels. If you've ever saved a selection to use later, this is what you've created. These are typically grayscale displays of saved selections and are useful for highlighting a difficult area that you may need to use again.

4. Spot. They contain instructions for using special ready-made paints, such as Pantone colors. If, say, you're a designer designing an ad for a new high-powered scooter that's bright red, you might want to create a channel containing that color to make sure it prints correctly.

At the bottom of the palette are the following controls:

• Load channel as selection. This button, which looks like a tiny dotted circle, selects all active content. This is useful if you are using the information to highlight complex areas. You can also load the content as a selection by Ctrl-clicking on the thumbnail.
• Save selection as channel. If you have an active selection, you can click this button to save the area as an alpha channel for future use. To assign a name, you can select the menu command Select => Save Selection or click on the button while holding the Alt key.
• Create new channel. This button looks like a small piece of paper with a folded corner. When you click it, Photoshop creates a new empty alpha channel. The program names the selections you create Alpha 1, Alpha 2, etc. If you want to enter a more memorable name, double-click the name and replace it.
• Delete current channel. When you click on this tiny trash bin, it is removed. Once you've adjusted the duplicate to create the perfect selection or layer mask, you can discard it by clicking this button (or you can leave it dangling but out of sight by turning off its visibility icon).

Just like any other palette, this palette has a menu in the upper right corner (its button looks like a down arrow next to four small lines). This handy menu includes all the commands mentioned earlier, plus a few of its own:

• New. This command creates a new alpha channel in the same way as clicking on the button described above at the bottom of the palette. The difference is that by selecting this menu command, you will open a dialog box in which you will need to assign a name and specify how the program should display information.
• Create a duplicate. If you want to create a copy so you can edit it, select this command. In this case, the program will display a dialog box in which you can assign a name and select its purpose (the same document or a new one). The destination option is useful when you are creating a displacement map or using channels to create a high-contrast black and white image.
• Delete. This command deletes the current channel or all if you selected several of them using the Shift key. However, you need to keep at least one, so if you select them all, Photoshop will darken this command.
• New spot channel. Useful for finished special printing ink called spot color. Read about this in the following articles.
• Combine with basic. Only letterpress presses can recognize spot prints, so if you need to print a proof on a regular desktop printer, you'll have to use this command first to merge.
• Options. This menu item is only available if an alpha channel is selected, and when you create or edit it, you can use the options to change how the selected or masked areas are displayed.
• Divide. If you need to separate each channel in an image into its own document, choose this command. Everyone uses Photoshop and copies it into new document in grayscale. This method useful when creating a black and white image.
• Merge. This team unites a maximum of four open documents in Grayscale mode into a single RGB document (if you have three documents open) or CMYK (if you have four documents open). You can also combine the feeds of all open documents into a multi-channel document. This command can be useful if you used the Split command to work on each of them separately, but now want to merge them back into one document.
• Panel Options. The palette automatically displays thumbnails. If you want to disable this function preview or set a different thumbnail size, select this menu item. If you have a large enough monitor (17" or larger), use the largest thumbnail size possible.

Using the Channel Mixer adjustment, you can create high-quality grayscale, sepia, or other toned images. You can also make a variety of creative adjustments to your images.

Using the Channel Mixer adjustment, you can create high-quality grayscale, sepia, or other toned images. You can also make a variety of creative adjustments to your images. To create high-quality grayscale images, select a percentage value for each color channel using the Channel Mixer adjustment. To convert a color image to a grayscale image or add a specific tone to it, use the Black and White command.

Channel Mix adjustment options modify the target (output) color channel using a mixture of the image's existing (source) color channels. Color channels are grayscale images that represent the tonal values ​​of the color components of an image (in RGB or CMYK mode). Channel Mixing allows you to add or subtract grayscale data from the source channel and modify the target channel with it. Colors are not added to or subtracted from a specific color component, as is the case with a Selective Color Correction adjustment.

Preset Channel Mixer presets can be found in the Presets menu in the Adjustments panel. Use default channel mixer presets to create, save, and load custom presets.

Mixing color channels

Create monochrome images from RGB and CMYK images

Monochrome images display color channels as gray values. Adjust the percentage for each channel to fine-tune the overall appearance of the grayscale image.

In this tutorial you'll learn how to increase contrast and toning by applying different Blend Modes with specific Color Channels. If you've used Photoshop before, you probably know that blending modes affect how a layer interacts with the previous layer, which is why the Blending Modes option is in the Layers panel.

We will tell you how to apply different blending modes not for the entire layer, but for individual RGB color channels (Red, Green, Blue), which the program needs to create a full-color image. All this is very easy to do thanks to the Apply Image (External Channel) command.

Working with color channels is not a section entirely for beginners, so if you are hearing this term for the first time, I advise you to first read articles about RGB channels. It will be easier for you to understand what is happening when working with the External Channel (Apply Image) window.

I'll be working in Photoshop CS6, but any earlier version of the program will work for this tutorial.

This is the photo that is currently open on my computer:

Original photo

Before starting any manipulations, I always make a copy of the layer with the original photo. If you look at my layers panel, you'll see that I always have the original photo on the Background layer:

Let's quickly create a copy of the layer using the keyboard shortcut Ctrl+Alt+J (Win) / Command+Option+J (Mac). This keyboard shortcut not only creates a copy of the layer, but also opens a dialog box where you can name the New Layer, we'll call it “Apply Image” and click Ok.

Now we see the new layer we just created in the Layers panel. Always name the layers, since the default names given by the program (Layer1, Layer2..) do not carry any information, which often causes confusion.

As I said at the beginning of the tutorial, we choose blending modes in the layers panel because we apply them to the entire layer. The Blend Mode function is located in the upper left corner of the Layers panel. Just as an example, I'll change the layer's blending mode from Normal to Soft Light:

We can see that the top Apply Image layer now interacts with the bottom Background layer in a new way. Soft Light mode belongs to the group of contrast blending modes, as it increases the overall contrast of the image. Color saturation has also increased slightly.

Photo after changing the blend mode toSoftLight.

Now let's go back to the original image and turn on the Normal blend mode again.

If blending modes affect the interaction of layers with each other, then what function do color channels serve, and how to use them? Take a look at the Layers panel and pay attention to its top part, you will see that the panel combines three tabs, including Layers and Channels. Select the Channels tab:

We've moved to the Channels panel, where the Red, Green, and Blue channels that make up our image are presented separately. The RGB channel at the top is not actually a channel, it is the end result of mixing the Red, Green and Blue channels, i.e. our photo.

In the panelChannels we can select individual channels for further work.

Select the Red channel

Selecting the Red channel temporarily disables the Green and Blue color channels, allowing us to see the photo only in the Red channel. Photoshop displays color channels as grayscale images, and each channel gives a different appearance to a black-and-white image. This is what the Red Channel looks like. If you compare this black and white version with the original full version of our photo, you will notice that areas containing a lot of red in the original image in the Red Channel appear lighter, while areas containing less red appear brighter. dark:

Black and white image in the Red channel

Now let's turn off the Red and Blue channels by selecting the Green channel.

Now the Green channel is displayed in the working window as a black and white image. Note that it looks completely different from Red. Again, if you compare the Green Channel photo to the original image, you will see that the areas where green is dominant appear lighter and, conversely, areas where there is no green appear darker:

Image in Green Channel

And finally, let's see what the photo looks like only in the Blue channel.

Select the Blue channel

An image opened in front of us in the Blue Channel, and again we see a black and white picture, different from the previous two. The more blue the area of ​​the original image contains, the lighter the area will be displayed in the Blue channel and vice versa. Remember that each individual color channel is a grayscale version of the image with its own brightness values:

Image in Blue Channel

To switch to a full color image, check the RGB checkbox at the top of the Channels panel.

Our full-color image appeared before us again:

Apply Image Command (External Channel)

Now that we know where to look for color channels and what they look like in grayscale images, let's answer the second part of our question: How do I apply channels to blend modes? As you may have noticed, there is no Blending Modes option at the top of the Channels panel. In fact, we don't need to leave at all open panel Channels, so we go back to the Layers panel:

To apply a blend mode to a single color channel, we will use the Apply Image command. You can find it in the top Menu panel, Image - Apply Image:

This will open the Apply Image command dialog box, which may seem a little confusing at first glance. However, we will only use two of its options: Channel and Blending.

In the Channel column we select the color channel we want to use. By default, the RGB channel is set in the menu, which, as you remember, is a composite channel (includes Red, Green and Blue). Below in the Blending column we select the blending mode itself. If we set the channel to RGB and select one of the layer's blend modes, we will get the same effect as if we selected the blend mode in the Layers panel. For example, I'll select the Soft Light mode and leave the channel as RGB.

We made sure that there is absolutely no difference between the effect that we got using the Apply Image command and the effect that resulted from using the blend mode in the Layers panel.

But, as you already understood, we can choose not RGB, but one of three color channels, so that’s what I’ll do. I'll leave the blending mode at Soft Light, but change the channel to Red.

Now we get a completely different effect. We still see high contrast, but what has changed? The model's skin and hair became significantly lighter than before. Her top and the yellow, orange and red parts of her jacket are also lighter now. Notice that the green and blue areas of the jacket have become darker on the contrary.

Let's see what happens if we change the channel to Green:

The opposite effect has occurred: parts containing green become significantly lighter, and areas with a predominant red or blue are now darker. A significant change occurred with the model's skin, which also became darker, due to which many details were drawn, which was not the case in the Red Channel.

We get the third version of our photo. Blue areas are now lighter, while red and green areas are darker. These variations of this effect would not be possible without access to the individual color channels provided by the Apply Image command.

Naturally, we can use not only the Soft Light blending mode, but also all the others presented in the list. I'll leave the Blue channel, but change the blending mode to Overly.