Channels in Photoshop and color. Selecting complex objects using Channels and Calculations

In this Photoshop tutorial I will show you how to cut out from the background complex objects using the Channels palette (Channels) and the calculation function (Calculations). This method of extracting objects from the background is very convenient because it saves a lot of time, unlike using other selection tools.

Let's look at the effect of this technique in practice and see for ourselves.

Why use channels to mask an image?

Photoshop has different selection tools: magnetic lasso, magic wand, quick mask, etc... why use channels for this purpose? The point is that using channels will save a lot of your time and make your work more accurate.

Most users of the program who retouch photos and process their own photos and photos of friends find it difficult to understand that the Channels palette can be used to create a Layer Mask (Layer Mask) because they just don't know what it is.

I won't explain what channels are, that's a topic for a separate lesson, but let me remind you that channels divide an image into three different brightness levels, corresponding to the three colors red, green and blue (Red, Green, Blue), which constitutes RGB mode. Let's look at the action of channels using the example of this lesson.

This is the result of the selection we should get:

Step 1.

Open the image of a tree branch on a blue background from the lesson resources in Photoshop and duplicate it (Ctrl+J). Rename the duplicated layer "Branches" layer. On this layer we will create a Layer Mask (Layer Mask) to hide the blue background on it by cutting out a branch from it.

Step 2.

You know you could use the Pen to highlight branches from the background? (Pen Tool) or Magic Wand (Magic Wand), but this selection technique will take a lot of time, effort and will lead to the formation of uneven edges of the object. Using Quick Mask (Quick Mask) also quite a troublesome task in our case.

Since we have a uniform background, it is appropriate to use the selection method using alpha channels. Even if you don’t understand anything yet, just follow all the steps with me in order and everything will become clear.

On the "Branches" layer, go to the "Channels" palette (Channels), which is located next to the Layers panel (Layers) by clicking on its tab.

Step 3.

You see in the palette that opens three layers of channels for each of the three primary colors of the image: red, green and blue (Red, Green, Blue), which are called alpha channels. The top layer of the "RGB" channel is a combination of all three alpha channels at once.

For high-quality selection of an object, we need a channel that will have the best contrast between the background and the branch. Go through all three channels one by one and select the one with the most contrast. In our case, the best option would be blue (Blue) channel because the contrast here is stronger between the background and the branch than in the other two.

Click on the blue channel, activating it.

Step 4.

With the blue channel selected, go to the Image-Calculations menu (Image>Calculations). This function will help us mix the alpha channels and show the preliminary result. Using the Calculation tool (Calculations) we will create a new alpha channel based on the three existing ones. Complete the settings from the screenshot below:

Let me explain what happens to our new channel with these settings. For source 1 (Source 1) The blue channel of the background layer and its duplicate is taken as source 2 (Source 2) Only the blue channel of the “Branches” layer is accepted, then they are mixed using the Multiply mode (Multiply) among themselves. The result of blending is a more contrasting image, which is the new alpha channel (Alpha 1). We are faced with the task of creating a sharp contrast between black and white flowers in the image, otherwise we will not be able to properly cut out the branch from the background and hide the background on the layer mask.

Step 5.

In the previous step we increased the contrast of the image, but this is not enough for our purpose. Let's increase it even more. On the "Alpha 1" channel layer (Alpha 1) again go to the Image-Calculations menu (Image>Calculations). This time we change the channel mixing mode to Overlay (Overlay) and perform the remaining settings of the option from the screenshot.

The resulting blending resulted in another "Alpha 2" alpha channel, in which the light areas became lighter and the dark areas darker, increasing the contrast between the background and the subject.

Step 6.

Even after two calculations we cannot select the branch because the sky has regions gray, and we only need black and white colors.

On the “Alpha 2” channel layer, go to the menu Image-Adjustments-Levels (Image-Adjustment-Levels) or press the combination Ctrl+L. Now we will get rid of the gray tint of the background, making it completely white. In the Levels dialog box, move the white Highlights slider (Highlight) left to 167 until the background is white.

Then, move the black Shadows slider a little to the right (Shadows) to 13, making a clear contrast between black and white.

Step 7

Now we have done everything we set out to do and are ready to select the branch and create a layer mask. Since we need to hide the background on the mask, and not the branch, we invert the colors in the image by pressing Ctrl+I on the keyboard. Now, load the branch selection by pressing Ctrl and clicking on the “Alpha 2” channel icon. A running stroke appears around the white branch, indicating that the selection has been activated.

Step 8

With the Alpha 2 channel still selected, click on the RGB channel to return the color to the image and return to the Layers palette. (Layers).

Step 9

All that remains is to hide the unnecessary background on the mask. To do this, go to the menu Layers - Layer Mask - Show Selection (Layer>Layer Mask>Reveal Selection) or click on the Layer Mask icon (circle in square) at the bottom of the layers panel. Once you create the mask, your background will be hidden on it. To see the result of background removal, turn off the visibility of the background layer by clicking on the eye of its thumbnail.

If you enlarge the image (Ctrl+), you will see how accurately the branches are selected in this way.

Step 10

The masking is done, and now we need to check the quality of the selection against a uniform background. Create a layer (Ctrl+Shift+N) above the background layer and fill (Edit-Fill or Shift+F5) color it in any color to see errors in the image.

Problem with tint.

If you want to use this image on another background or in a collage, then there is a problem with the presence of an unnecessary blue tint on the branches, which must be eliminated. To give you an idea of ​​what I'm talking about, I've chosen a different stock image for the background.

Removing unwanted tint in Photoshop.

There is an easy way to remove unwanted tint from an object using Hue/Saturation adjustments. (Hue/Saturation) and decreasing the layer mask. If the shade is located at the edges of the object, it will be enough to reduce the mask by 1 px and the problem will be solved.

Since we already have a mask on the "Branches" layer, we can't create another one. But there is a way out. We'll create a mask on the group layer later.
Select the "Branches" layer and place it in a group by pressing Ctrl+G on your keyboard.

Load a selection mask on the "Branches" layer (Ctrl+click on the mask icon), then go to menu Select-Modify-Compress (Select>Modify>Contract), set the compression to 1 px. Next, create a mask on the layer with the group and to do this, go to the menu Layers-Layer Mask-Show Selection (Layer>Layer Mask>Reveal Selection). In the Layers panel, you can see your new mask on the layer with the group.

If your image is low resolution, 1px compression may remove fine detail from the subject. In this case, you need another way to remove the unwanted tint.

After we cut down our mask, the blue tint is still present on the branches. Let's try to remove it using the Hue/Saturation correction. (Hue/Saturation), discoloring blue and cyan tones or changing this shade to another.

Finally, take a look at the result before and after applying compression to the mask and creating an adjustment layer.

I hope you found something new for yourself in this lesson and will now successfully use this method of highlighting complex objects.

Using Channels in Photoshop

The article about channels is intended for beginners working in Photoshop.

Channels (the Channels palette in the program Adobe Photoshop used to store service information: color and transparency levels. Using the information in the channels, you can evaluate the image quality, as well as apply various utility algorithms to eliminate defects. You can also save the shaded selection as a raster map and load it for work at any time.

Color channels

Channel- halftone (grayscale) raster image, used to store service information. Service information is color, transparency levels, service masks.

The contents of the channels are displayed in the Channels palette.

Photoshop renders a full-color image not as a single set of dots, but as three or four "channels" (grayscale) of pixels. The content of the channels depends on the color model of the image.

For example, an RGB image consists of red, green, and blue colors, each of which is represented as a separate grayscale image. Similarly, a Lab image contains three channels, one of which corresponds to brightness, and the other two to chrominance. A CMYK image consists of four channels, each corresponding to a specific color of the dyes used in printing.

Channels correspond to the characteristics of a particular output or input device. For example, the channels of the CMYK model correspond to the different matrices with which the image is printed. The cyan matrix prints the image with cyan dye, the magenta matrix prints magenta, the yellow matrix prints yellow, and the black matrix prints black. Each RGB channel corresponds to a pass over the image of a scanning element of the corresponding color. The only mode that is not tied to any device is Lab mode. Its channels are pure abstraction.

Composite channel— standard mode, in which all color channels of the current color model are available for editing.

RGB image color channels

Let's create new document 600x600 pixels in size, color model - RGB, background content - background color (black) - Ctrl+N.

Let's go to the "Channels" palette. We activate the Red channel when all channels are visible.

Select a brush with a diameter of 250, hard, white.

Click on the image.

You noticed that Adobe Photoshop associated white with the Red channel active as the maximum color content. Remember the color RGB model: monitor model, maximum color is described in white, lack of information is described in black.

Activate the Green channel when all channels are visible. Click the white brush in the image.

Activate the Blue channel when all channels are visible. Click the white brush in the image.

The result is an image where the maximum colors set with a white brush are the primary colors of the RGB model: red, green, blue. You also see that the intersection of these colors gives secondary colors, and the sum of all colors in the image (the intersection of the colors in the center) is white (remember that the maximum color with coordinates (255; 255; 255) is white).

CMYK image color channels

1. Open a photo of a parrot in the CMYK color space.

In the Channels palette you can see four color channels corresponding to the CMYK print and ink model.

2. In the CMYK model, everything is the other way around: 0 - maximum color, black content of the channel.

In the CMYK model, secondary colors are obtained by summing the primary colors according to the scheme: C + M = B (blue); C + Y = G(green); M + Y = R (red).

Customizing colors

The Color Settings dialog box is where you set some very important settings for how Photoshop displays and converts colors. A clear understanding and selection of the correct parameters is the key to successfully working with color in Photoshop and ensuring correct color reproduction in your images. This dialog box is one of the most important windows in the program. The settings you specify affect how images are opened, how pixels are inserted from one image to another, how colors are displayed on the screen, and how the user is notified when colors change as a result of a particular operation. Therefore, you should definitely understand the purpose of the various options available in the Color Settings dialog box.

How Photoshop works with color

Before we dive into the details of the Color Settings dialog box options, let's look at some more general issues. It would be wrong to simply tell which checkboxes to check or which radio buttons to select; After all, you need to have knowledge of the conceptual capabilities of the Color Settings dialog box and color management in Photoshop. At the most basic level, a digital image is nothing more than a collection of numbers. The image contains a grid of pixels, as well as information about the color of each pixel (or tint, in the case of a grayscale image), represented as a numeric code. In the case of RGB images, each pixel has three values, one each for red, green, and blue. Of course, working with an image in Photoshop is much nicer than working with a bunch of numbers, but when you edit images, you are actually changing the characteristics of the pixels. The numbers assigned to pixels tell Photoshop exactly how each pixel should appear on the monitor screen; numerical values ​​are also used when printing an image. The problem with this approach is some ambiguity. When using watercolors, oils, colored pencils or crayons, the images look different. In the case of digital images, specific shades depend on whether the image is displayed on a monitor screen, printed on an inkjet or photo printer; Moreover, everything also depends on specific devices. To standardize the display and printing of colors, Photoshop's color management system is based on four key principles.

1. Control your work environment thanks to stable lighting conditions and neutral wall colours.

2. Have a properly calibrated monitor with the correct profile that tells Photoshop how to display color.

3. Use of an RGB workspace that is independent of specific devices; this means that the interpretation of the shades determined by the given numbers does not depend on a specific device such as a monitor, scanner or camera.

4. Adding ICC (color descriptors) profiles, which tell Photoshop and other ICC-compatible applications how colors should be displayed in an image.

The importance of monitor calibration and color proofing

The importance of controlling your viewing environment and having a calibrated monitor with the correct profile cannot be overstated. Just imagine the following situation: your monitor is not calibrated and its profile is inaccurate. IN in this case There is no need to talk about color accuracy. If you have never created a profile for your monitor (at a minimum, all you need to do is use the calibration utility that comes with your monitor). operating system), I recommend that you refrain from performing complex printing tasks until the appropriate operations are completed.

Workspaces

The workspace determines how Photoshop interprets numeric color codes and also ensures visual consistency of shades. The workspace affects all new images created in Photoshop, as well as images that have not been assigned a color profile (which is often the case with images taken with a digital camera). Because the workspaces available in Photoshop do not represent colors as defined by a specific device, such as a monitor or printer, displaying correct shades on a calibrated monitor screen is only possible if you use an accurate monitor profile and save together with a color profile image (details).

Color profiles

If you put five people in one room and ask them to close their eyes and imagine the color purple, it is unlikely that they will all imagine the same shade. In addition to obvious differences in brightness, such as light magenta and dark magenta, there may also be differences in hue and saturation. Are we talking about a dark purple shade with a blue tint, or about purple with a hint of lilac? Without being able to accurately determine the color, many definitions of purple can be obtained. To obtain a more accurate description of the shades, it is necessary to add some additional information. In the case of digital images, the ICC profile acts as a source of additional information, which allows us to talk about the correct interpretation of the colors in the image. A color profile is a description of exactly how different shades should be displayed on screen or printed. In addition to the monitor profile and device-independent workspace, the color profile is the third critical component in ensuring that the tones of an image are handled correctly in Photoshop. Any file you work on in Photoshop must be saved with the embedded color profile (the corresponding option is available in the Save As dialog box). Having a profile tells Photoshop and other ICC-compatible applications exactly how the shades should look. I don't even know how to emphasize the importance of matching the color profile to the image. Color management experts Bruce Fraser and Andrew Rodney believe that without an embedded profile, the file is simply an RGB "mystery object." Photoshop has no idea how to display different shades, so when displaying them it is guided by the parameters of the current workspace, which cannot always be set correctly.

ADJUSTING COLOR IN PHOTOSHOP

Adjusting colors in Photoshop is often overlooked by self-taught users when mastering the program. People can usually get by without any knowledge about it. Is it really worth knowing about adjusting colors in Photoshop?

The answer to this question depends on how seriously you intend to work in Photoshop. If you want to become a professional, then any additional knowledge will give you an advantage when working in the program. Basic knowledge can make your work in Photoshop much easier.

Therefore, in this tutorial I will give the basics that you need to know about adjusting colors in Photoshop.

In order to set up the color management system in Photoshop, you need to run the command Edit - Color Settings (Ctrl + Shift + K).

By default, the window that opens will have the following settings:

Let's look at all the settings in more detail.

WORKING SPACES

RGB

RGB colors are created by adding to black, which is why this color model is called additive. It is very suitable for display on a monitor screen.

You will most likely have the SRGB IEC color profile installed by default. It is good for most simple Photoshop tasks, but does not provide a rich color palette.

For web designers and photographers, it is better to use the Adobe RGB profile (1998). It offers a wider color range.

The difference between them is still not so significant, it’s just that the SRGB profile was created for less expensive displays.

Nowadays, more and more photographers are choosing to use the ProPhoto RGB profile.

It has a much larger range of colors, some of which are actually beyond human vision. However, it has its drawbacks. One of them is that when converting color gamut, using this profile may end up producing undesirable results. Therefore, before you start working with this color profile, you should gain some additional knowledge about working with it.
Also, do not confuse sRGB IEC with Monitor RGB - sRGB IEC (Monitor sRGB IEC). If you choose the second option, you may get different results on different displays.

CMYK

The CMYK color model is based on the fact that the sheet of paper itself is white, i.e. reflects almost the entire spectrum of RGB, and the paints applied to it act as filters, each of which “steals” its own color (red, green or blue).

CMYK colors are determined by subtracting one of three RGB colors from white.

The CMYK system was created and used for typographic printing. Before sending to print, make sure your image looks correct in the CMYK color profile.

The default here is U.S. Web Coated (SWOP) v2.

You can select the “Load CMYK” option and load the one you need.

GRAY / SPOT

Leave the Dot Gain at 20%.

COLOR MANAGEMENT STRATEGIES

There are three settings you can configure here. Let's look at them in more detail.

OFF

If you select this option, the embedded color profile (or lack thereof) will be ignored and the image will be saved without a color space description.

SAVE BUILT-IN PROFILES (PRESERVE EMBEDDED PROFILES)

This option will allow you to take into account the embedded color profiles and use them when processing images. Newly opened images are in the color space described by the color profile embedded in the file.

CONVERT TO WORKING RGB (СMYK/GRAY)

If the embedded color profile in Photoshop does not match the working color space, the program converts the image from its color space to the working one, assigning it a color profile corresponding to the working color space.

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Click on the “More options” button on the right, under the “Ok” button, to expand the color settings panel completely.

After clicking this button, new fields will appear.

CONVERSION OPTIONS

MODULE (ENGINE)

Designed to select a color management system to apply color transformations. It is preferable to choose the Adobe (ACE) option, which corresponds to the color management system built into Photoshop.

METHOD (INTENT)

This setting determines the method used to convert color between spaces. The most commonly used methods are Relative Colorimetric and Perceptual.

Relative colorimetric(Relative Colorimetric) - when choosing this option, all colors falling outside the color range of the output device are cut off, and the closest ones are substituted instead. All other colors remain unchanged.

Perceptual(Perceptual) - in this case, the visual relationships between colors are preserved. Absolutely all colors received from the input device are converted to their equivalents within the color range of the output device.

Use black point compensation(Use Black Point Compensation)

When you select the Use Black Point Compensation check box, the darkest of all neutral colors in the source color space is converted to the same color in the target space. This is very important for maintaining black color during various transformations.

COLOR PROOF OPTIONS (PROOF SETUP)

Allows you to set proof print settings.

Located in the View menu - Proof options (View - Proof Setup).

With this function, you can see a preview of the image on the screen in accordance with the set color profile of the output devices that are available in the operating system.

The screen version will give a fairly accurate idea of ​​how the image will look after printing.

To quickly turn it on and off, use CTRL combination+ Y (or go to the View menu - Proof).

If your colors look strange, check that you haven't accidentally turned this feature off. If at the end of the file name you see backslash with a color profile, then you have found the reason.

In the "Proofing Options" section there are various settings.

CMYK shapes (Working CMYK) allows you to create a proof based on the CMYK workspace as defined in the Color Settings dialog box.

Mac/Win RGB
commands let you estimate how an image will look on a Mac and Windows monitors. Can be quite useful when you are developing a cross-platform project.

Custom- When you select this option, the following dialog box will appear:

Using these options, you can customize the soft proofing mode for any device.

Simulate paper color(Simulate Paper Color) - When you select this option, Photoshop will try to display on the display the color of the paper on which the print will be made. The quality of such a prediction strongly depends on the quality of the profile, since this is the only source of information from which Photoshop can get information about the parameters of the paper.

Simulate black paint(Simulate Black Ink) - performs a similar function, only Photoshop tries to display on the screen the darkest possible color that can be obtained on the target device.

MANAGING COLOR PROFILES

CHECKING THE COLOR PROFILE INFORMATION OF A FILE

So, we learned how to adjust color in Photoshop.

Now let's see where to find out information about which color profile is embedded in the file currently open.

Open any image.

In the lower left corner of the main Photoshop window we find a small panel for displaying various information.

Click on the right arrow, select Document Profile in the menu that appears, and information about the ICC profile will appear on the screen:

ASSIGNING/CONVERTING COLOR PROFILES

Used to assign or transform a file's color profile.

Performed by the command Edit - Assign profile (Convert to profile) Edit - Assign Profile / Convert to Profile.

Here's the most important thing. Now you have a basic knowledge of how to adjust colors in Photoshop, as well as what color profiles are and how to use them in your work.

Color information in Photoshop is stored in what are called channels. A channel is an image in which the points for each component color of a color model determine the brightness (amount) of that color. This is not easy to understand right away. Let's try to explain it more clearly.

Depending on the color model, an image may have three color channels (for RGB) or four (for CMYK). Each color of the model is allocated a separate channel, each channel contains a gray copy of the image. In channels, the gray level can have 256 gradations. The brightness of the gray point indicates the amount of color corresponding to the channel in the composite image. How lighter point, those more The color of this channel is used in the resulting point.

1. Upload any color image. If the image you uploaded was created in the CMYK color model, convert it to RGB.

2. Open the palette Channels. You see four points: RGB, Red, Green And Blue. Red, Green And Blue- these are the channels of your image.

3. Uncheck the eye-shaped channels for channels RGB, Red And Green. You will only have the channel on Blue(Fig. 7.1).

Rice. 7.1. Blue channel displayed

MULTIMEDIA COURSE

The “Color Channels” chapter on the CD included with the book contains several video lectures on working with color channels.

Notice that the image in the document window has turned gray. Moreover, it bears little resemblance to an ordinary black and white image. Some areas that seem to be light are dark, and vice versa. The thing is that grayscale shows how much blue color is involved in the formation of each color point. The lighter the dot, the more blue it contains. If there are completely black dots, it means that in the resulting color of these dots there is no blue at all or it is negligible. Look the same way Red And Green channels. You will see that the brightness of certain parts of the image does not correspond to reality. Let us emphasize once again that in this case the brightness of a point is determined not by the brightness of the resulting point, but by the brightness of the color of a given channel at this point.

Let's do a simple experiment.

1. Create a new image with a white background.

2. Select a tool Pencil. Adjust the brush so that the pencil line is thick enough, for example 50 pixels

3. Choose a pure red color. To do this, in the color selection dialog box, specify the value R equal 255 , and the values G And B equal 0 . This is a color that consists only of red subpixels. Blue and green subpixels do not participate at all in this color (their brightness value is zero).

4. Draw a line in the window of the created document.

5. Open the palette Channels, then watch each channel separately.

Now let's describe what you should see.

Channel Red. You see a completely white image without any lines. The white background of the image indicates that the color white contains maximum level red (255). You also don’t see the line, since you drew it with a color in which the amount of red is also 255, that is, in this channel the intensity of the red subpixels is maximum over the entire area of ​​the drawing.

Channels Green And Blue. The backgrounds of these channels are white, since the participation of blue and green colors in white is also maximum (recall that white color is obtained when the value of all three RGB components is equal to 255). The line you drew in these channels is black. When you selected the tool color, you specified zero values ​​for the colors G And B, that is, the blue and green colors do not participate at all in the color you choose. This is why the line in these channels is black; this indicates that the level of the corresponding colors in these channels is minimal.

Now display simultaneously Red And Green channels. The background of the image is yellow and the dot is red. This is the result of mixing channels, that is, now we have superimposed Red channel on Green and at the same time excluded Blue channel. As a result, we added 255 gradations of red with the same amount of green and thereby obtained a yellow background. The line remained red because by 255 gradations of red in the channel Red added 0 gradations of red from the channel Green, that is, nothing was added.

If you add up the channels Green And Blue, excluding the channel Red, we get a turquoise background (the result of adding 255 gradations of green and blue) and a black line. Neither blue nor green colors are present in the line we drew (the level of these colors in the corresponding channels is zero), so the line remains black.

We will see a similar picture if we create an image in the CMYK color model. Only the CMYK channels, unlike RGB, are inverse, that is, the black and white colors in these channels are swapped. White color means the complete absence of dye, and black means the maximum amount of dye (100). For example, if we create an image with a white background and a purple line (C = 0, M = 100, Y = 0 and K = 0), we will see the following in the channels.

Channels Blue, Yellow And Black will be completely white. These colors do not participate in the formation of a white background (the paper is already white on its own).

Channel Purple will contain a black line on a white background. This color also does not participate in the formation of the background, but in the line color the intensity of the purple color is maximum.

If we apply to white background line of a different color, for example green, then in CMYK channels this line will be gray with different brightness. Green CMYK is not present in the model, so it is obtained by mixing primary colors. The degree of brightness in each channel will depend on the amount of the corresponding color in the resulting green. The more of a certain color participates in the formation of the resultant, the darker the line in the corresponding channel will be. IN to a greater extent The green color includes blue and yellow. The proportion of magenta and black colors is not very high, so the lines on these channels will be very pale. Of course, it still depends on the shade of green. It is possible to create a color that has zero proportions of black and magenta, and it will be pure green.

We've talked about channels for so long, but we still haven't explained why they are needed. You may not use them at the initial stages and look at the palette at all Channels. Many people have been working with Photoshop for years and are completely unaware of the purpose for which channels are used, if not even aware of their existence. We agree that for an amateur this is not so important. However, when you reach professional use Photoshop programs and especially if you work in organizations that produce printing products, you will certainly come across such a concept as color separation. This is where you need channels.

Using channels it is very convenient to adjust the color scheme of an image. For example, when working with an RGB photograph, you notice that in a certain area the red color predominates. This is not easy to correct using conventional methods (levels) or other color correction. Yes, and it’s not always convenient. Turn off all channels except red, and, for example, the tool Dimmer you shade a given area of ​​the image, that is, you shade only the red color, thereby reducing the level of red in the composite color. You don’t even have to turn off other channels at the same time: just select a channel Red. However, with disabled channels it is easier to control your work.

Another use for channels is color separation. To print a picture on printing equipment, four gray images are required. These are exactly the channels we were talking about: CMYK channels. Typically, one image is printed on four transparencies and the contents of one channel are applied to each film. Next, based on the intensity (level) of black on each of the films, the equipment applies the appropriate amount of dye to the media, most often paper (Fig. 7.2).

Rice. 7.2. This is what the image looks like in individual CMYK channels.

It is not by chance that we use the term “media”, since the image can be printed on fabric, plastic and various polymer materials.

You can add to the image new channel. However, this will not be a color channel, but a so-called alpha channel, or a mask channel. What can such channels be used for? There are many applications. The simplest thing is to use masks for images or high-quality retouching of graphics.

Try creating a new channel by clicking the third button from the left at the bottom of the palette Channels. Most likely, your entire image will appear to be covered with a translucent color film, and a new channel will appear in the channel list Alpha 1.

1. Now, having previously selected the channel Alpha 1, try to take the tool Eraser and erase part of the image. In the place where I “walked” Eraser, the image with the original colors will appear. In other words, you have created a semi-transparent alpha channel and made certain parts of it transparent (Figure 7.3).

Rice. 7.3. Part of the mask channel has been erased with an eraser.

2. Press the keyboard shortcut Ctrl+A, the entire image will be selected, and press the key Delete. The alpha channel content will be removed and the image will appear in its original colors.

3. Deselect by pressing the keyboard shortcut Ctrl+D.

4. Select a tool Brush and define a blue color for this tool.

5. Make sure the channel Alpha 1 is still highlighted.

6. Make a few strokes with the brush.

Please note that strokes appear in the image that are different from the color you selected, most likely red, that is, by “painting” with a blue brush, you can get red shades of strokes. This happens because the color of the brush is not actually blue, but a certain shade of gray. Take a look at the color swatch at the bottom of the toolbar to see for yourself. By adding gray lines to the alpha channel, you increase the brightness level of areas of the alpha channel's base color (red by default). As a result, the color of the channel is summed with the other channels.

Now a little about the alpha channel settings.

To call the alpha channel settings dialog box (Fig. 7.4), you need to double-click on the thumbnail of this channel in the palette Channels.

Rice. 7.4. Channel Options Dialog Box

The color swatch immediately catches your eye. The default is red. This is the alpha channel color. Remember that, no matter what brush color you choose, when you paint with the brush, red lines of varying brightness appear on the alpha channel (the brightness depends on the selected hue). You can change this color and then the lines drawn on the alpha channel will have a different color (of your choice).

In the area Show in color by default the switch is set to position Masked areas. How does the alpha channel work? this mode when drawing or erasing, you saw. If you select the position Selected areas, the alpha channel will act on the image in the opposite way, that is, the painted areas will become transparent, and the unpainted ones, on the contrary, will be opaque or translucent.

In the field Opacity indicate the degree of opacity of the alpha channel. By default, the opacity level is 50 % , which is why you can clearly see the image through “color film”.

It should be noted that you can create many alpha channels, adjust their opacity and color, and then apply any strokes or images in these channels. You can also copy the contents of any channel into an alpha channel, apply various corrections to it, etc. All this allows you to very finely adjust the color parameters of the image, create original drawings, etc. If you really want, you can even turn black white image to color. To do this, you need to convert a black and white image to an RGB or CMYK model, create the required number of alpha channels (according to the number of colors in the model), copy the image into these channels and colorize individual fragments of the image so that when mixing the channels you get the desired colors. This, of course, is not easy and will require a lot of time, patience and experience, but it is possible! Indeed, you can turn an old black and white photograph into a color one. By the way, if all color channels contain absolutely the same information, it means that the proportions of all colors at individual points are equal. And the same proportions of colors are always a gray dot (in different gradations of brightness: from white to black). In other words, if the images in all color channels do not differ from each other, then the picture is black and white.

The use of color channels in retouching allows you to make spectacular transformations and greatly simplifies processing. Every retoucher should master the skill of working with image channels. Before we start processing using color channels, let’s clarify what it is.

Any digital image can be represented as color channels. In the case of the RGB color mode, these are red, green, and blue (red, green, blue), the mixing of which gives us all the other known shades.

Each channel is an image of one of the colors. The computer processes the channel information as a separate monochrome image. Each channel can contain 256 shades of color at 8-bit color resolution, 65,536 shades at 16-bit or 4,294,967,296 at 32-bit. Each pixel in a channel has a specific gray value. So when you look at a single color channel in Photoshop, you see it in black and white. The more a certain color(red, blue, green) is contained in the entire image, the lighter the pixel in the channel. Less means darker.

Let's apply retouching to the image, that is, we will enhance the highlights and shadows to make the photo more expressive.

Let's put the main emphasis in this photo on the smoke. To do this we need to select it. It sounds a little scary, but it's easier than it might seem. And it’s all thanks to the channels.

Open the image in Photoshop and create a duplicate layer Ctrl+J to compare the results later. Let's immediately save it as a PSD so as not to lose data ( Shift+Ctrl+S, then select PSD format).

We remain on the duplicate layer and go to the Channels tab.

As we already said, each color channel is visible as black and white image. The lighter its areas, the more of the corresponding channel color they contain. We need to select the most contrasting channel. Let's look at them all one by one. To do this, we will leave only one channel visible each time (by clicking on the eye image opposite each one).

The blue channel has the highest contrast, so let's create a duplicate of it. Grab it with your mouse and drag it onto the icon for creating a new channel.

We will have a duplicate of the blue channel.

We remain on the duplicate channel and click Ctrl+L. This will bring up the channel levels settings.

A raster image, and in this case the image of our photos, consists of dots. These dots each have their own color. The black, gray and white points in the image are responsible for saturation, brightness and light. Levels allow you to change the point value level. Level 0 - black pixels, 255 - white. Level 128 - gray. The remaining levels range between 0 and 255. Redistributing the levels changes the tonal range of the image.

In channel levels we can adjust the black, white and gray points. The black point is on the left under the diagram, the gray point is in the center, and the white point is on the right.

Using levels we will make the dark areas darker and the light areas lighter. You need to darken it so that the smoke is significantly separated from the background, but details are not lost. To do this, under the diagram, move the left slider (black point) to the right, and the right slider to the left (white point). In our case, the sufficient effect will be the result that you see in the image below.

Notice how dark the background has become and how the smoke has lightened. Click Ok and close the window. Now, holding Ctrl, click on our channel. We see how the dotted selection lines appear. This means that we have highlighted the light areas of the image. And even if you don't see all the dotted lines, the entire light area is actually highlighted. Without removing the selection, turn off the visibility of the duplicate channel, turn on the visibility of all others, go to the tab Layers/“Layers”.

While in the layers palette, press the combination Shift+Ctrl+N to create a new empty layer. Let's stand on it. The highlight dots are still visible.

Now select a tool Brush(key B), soft, white color. And we draw along the smoke, along our selected area. It is important for us to draw exactly the smoke.

Feel free to paint with a brush. The drawing will only affect the selected area, and these are our light areas, which we selected using the channel.

Notice how much better it becomes visible. If there is too much of this, we will reduce the visibility of the layer. Now, without deselecting the selection, press the combination Shift+Ctrl+I and then Shift+Ctrl+N. So we invert the selection and instead of the light area, select the dark one. The second combination will create another new layer. Next, change the brush color to black and paint the background on a new layer and a new selection.

Now we press Ctrl+D

Now all our attention turns to the smoke, since it has become much more clearly visible. In the same way, you can enhance light and shadow in portraits, in images of glass objects, and water. This will add drama to the image.

You can learn even more about Photoshop in the Fotoshkola.net course “Photoshop CC: Working with Channels and Filters.”

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 visibility 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 powerful 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 clicking and holding Ctrl key, in miniature.
• 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 have selected several of them using Shift keys. 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 select each channel in an image in own document, select this command. Photoshop uses each and copies it into a new document in grayscale. This method is 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.