In this lesson, we will learn how to enhance the contrast and brightness of images in non-standard ways by applying blending modes to individual color channels. If you are familiar with Photoshop, then, of course, you know that we usually select blending modes on the layers panel when we want to change the interaction or combination of the layer with the underlying layer / layers.
I will show you how to apply blend modes not to the whole layer, but to the individual color channels of the RGB model (red, green, and blue channels) that Photoshop uses to create a full-fledged color image.
How do we apply blending modes to color channels? In fact, this is easy and simple thanks to the “External Channel” command (Apply Image).
Working with color channels in Photoshop is a bit difficult for a novice user. I will superficially touch it in this lesson, but for those who are just starting to work with channels in Photoshop, I strongly recommend that you familiarize yourself with the lesson first. “Model RGB and color channels ». After reading the material, you will better understand what will happen with the further work with the “External Channel” dialog box in this lesson.
To learn more about blending modes, I recommend that you familiarize yourself with the lesson about blending modes, This explains how the basic blending modes work in Photoshop.
In this tutorial, I’ll work in Photoshop CS6, but later versions will work too. Here is a photo that I have now opened in the program:
The first thing we need to do before proceeding to further work with the image is to create a copy of it. If we look at the layers panel, we note that the original image is placed on the Background layer:
Let’s quickly make a copy of the background layer by pressing Ctrl + Alt + J / Command + Option + J on the keyboard. This action will not only create a copy of the layer, but also pre-open the new layer dialog box in which we can name the layer before adding it to the panel. Name the layer “External Channel” (Apply Image), then click OK to exit the dialog box:
If we look at the layers panel again, we see that a copy of the image appeared on the new layer “External Channel” located above the background layer. It is always better to assign visual, “speaking” names to the layers, which we did, otherwise you can easily get confused with the common names that the program itself gives layers, such as Layer 1, that won’t tell us anything about the purpose of the layer:
As I mentioned at the beginning of the lesson, we usually select blending modes on the layers panel, because, as a rule, we apply them to the whole layer. The overlay selection button is located in the upper left corner of the layers panel. As an example, I now quickly change the blending mode of the “External Channel” layer from Normal (Normal) (default) to Soft Light mode:
The mode change shows the interaction of two layers – the “External Channel” layer and below the positioned background layer. The “Soft Light” mode belongs to the group of contrast enhancement modes, as it increases the contrast level of the entire image, which we see in our photo. Color saturation also increased slightly:
I will change the blending mode back to Normal to return the original settings:
Thus, if changing the blending modes on the layers panel affects the interaction of the layers as a whole, where does working with individual color channels affect and how to use blending modes for the channels? In order to answer the first part of the question, we need to take a closer look at the layers panel. We will see that it is located next to two other panels – Channels and Paths (Channels and Paths), each of which has its own icon. Click on the Channels panel icon:
This action will switch to the channel panel, where we can see the individual color channels: red (Red), green (Green) and blue (Blue), which make up our image. The RGB channel at the very top is not really a channel. It is the result of the fusion of red, green, and blue channels, or in other words, this is how we see a full-color image (each color in the image consists of a combination of red, green, and blue):
We can select a single channel by simply clicking on it. I’ll click on the red channel to select it:
Selecting a red channel temporarily turns off the green and blue channels and allows us to see only the red channel in the document window. Photoshop program displays color channels in the form of halftone images, and each channel is an image with different shades of gray. This is what my red channel looks like in a document window. If you compare this version of the image with a full color image, you will notice that the areas containing red in the color image are lighter in halftones, while areas that contain little red or no red color, look darker:
Next, I will select the green channel on the channel panel, which will entail a temporary shutdown of the red and blue channels:
The document window now displays a green channel in the form of a halftone image. Please note that it differs significantly from the red channel. And again, if you compared this image with a color variant, you would notice that areas containing a lot of green look lighter in grayscale, and areas with a little green or no color appear darker:
Finally, I will click on the blue channel in the channel panel to select it, as a result of which the red and green channels are temporarily turned off:
Now we have a blue channel in the document window, and again the halftone image is different from the red and green channels. This time, the more blue the area on the color image contains, the brighter it is in the image in the gray gradation, and vice versa, the less blue in the color image area, the darker the area in the half-tone image. When you will soon choose a separate color channel in the dialog box of the “External Channel” command, do not forget about these three versions of the color channels, represented by half-tone images with different grayscale:
To go to the full color version of the image, click on the RGB channel at the very top of the channel panel. This action will return all three color channels to work:
And we again see the full color image:
“External Channel” command
Now that we know that the color channels are located on a separate panel and each of them is a halftone image, let’s answer the second part of the question – how can we apply blend modes to them? You may have noticed that on the channel panel there is no “Blend Mode” tab as opposed to the layers panel. In fact, we no longer need to work with the channel panel, so let’s switch back to the layer panel by clicking on its name (Layers):
To apply blending modes to individual color channels, we use the External Channel command. To do this, select the menu line “Image» (Image) in the upper part of the screen, then from the list – “External Channel” (Apply Image):
This action will open the External Channel command dialog box. If you have never worked with him before, then it may seem a bit intimidating to you, but in fact everything is quite simple. In fact, we will use only two parameters – “Channel” (Channel) and “Overlay” (Blending):
The Channel parameter is responsible for selecting the channel we want to use for work. By default, the selected channel is RGB, which, if you remember, is a mixed channel located at the very top of the channel panel (the result of merging the red, green and blue channels to produce a color image). The “Overlay” parameter is responsible for selecting the desired overlay mode. If we leave the “Channel” parameter with the selected RGB channel and just change the blending modes, we get the same result as when choosing the blending mode on the layers panel. For example, I will select the Soft Light blending mode in the External Channel command dialog box (the Channel parameter is RGB):
It is clearly seen that my image is no different from the one I received when choosing the “Soft Light” blend mode on the layers panel earlier in our lesson. The same increase in contrast and color saturation occurred:
But everything becomes more interesting when instead of the RGB channel we choose any of the three separate color channels. I will leave the blend mode “Soft Light” and change the “Channel” parameter from RGB to “Red”. Thus, I will overlay only the red channel:
This time the result is completely different from the previous ones. We still see a general increase in contrast due to the operation of the “Soft Light” blend mode, but due to the interaction of the red channel’s halftone image with the blend mode, we have a different effect. The skin of the girl looks much lighter than before. The same thing happened with her hair, with a red top and areas of red, orange and yellow shades on the jacket. In essence, everything that contains a lot of red in the image now looks brighter, while areas containing a little red or not having it at all, for example, the blue and green areas of the jacket, look darker than before:
Let’s see what happens if I change the value of the Channel parameter to green (the blend mode is still Soft Light):
By selecting the green channel, we got another option for applying the effect. This time, areas that contain a lot of green are brighter than steel, while areas with lots of red or blue are darker. The most distinct change occurred with the skin of a girl who became darker and more contrast than when choosing a red channel:
Now I will replace the value of the Channel parameter with blue:
In this case, we received the third version of the image, when the areas with blue color became lighter, and the areas with red or green colors became darker. These variations of the effect would not have been possible (at least without much effort) if we had not gained access to working with individual color channels using the External Channel command:
Of course, we are not limited to using only the “Soft Light” blend mode when working with our color channels. We can choose any of the blending modes, as we would have done on the layers panel. I will leave the value of the “Channel” parameter – “Blue” and change the value of the “Overlay” parameter to “Overlay”:
Like the Soft Light mode, the Overlap mode is a mode that enhances the contrast in the image, but to an even greater degree:
And this is how the operation of the “Overlap” mode will look when the channel changes to “Green”:
And this is what the red channel looks like in the “Overlap” mode:
The image of the red channel looks too saturated when interacting with the “Overlap” mode, but we can, if necessary, easily mute the colors, reducing the opacity of the overlay. You will find the Opacity parameter directly below the Blending parameter in the External Channel command dialog box, and it works the same way as the Opacity parameter on the Layers panel. The default value of the parameter is 100%. I will reduce its value to 60%:
Reducing the opacity, we returned part of the highlights and shadows to the image:
If you want to compare the processed and the original image, simply disable the option “Preview” (Preview) located on the right side of the dialog box. This action will hide the effect and give you the opportunity to see the original image in the document window. Select the Preview option again to return to working with the effect:
You will often notice, especially when processing photos of people, that the Soft Light and Overlapping modes are most suited for processing, but other useful blending modes are also worth trying, such as Screen and Multiply. . The “Screen” mode lightens everything in the image, while the “Multiplication” mode dims. Try applying these modes to the three color channels to see the result, then adjust the intensity of the effect, increasing or decreasing the opacity value. For example, in my case, I set the value of the Channel parameter to green, the blending mode to Multiply and reduced the opacity to 40%:
As a result, the image became darker and more traced in details:
When you are satisfied with the result, click OK to exit the “External Channel” command dialog box. You can then again compare the processed image with the original one by clicking on the layer visibility icon (as an eye) located to the left of the layer name “External channel” on the layers panel. Click on the icon once to make the layer temporarily invisible and view the original image. Click the icon again to return visibility to the “External Channel” layer:
And so we did it! We learned how to apply blending modes to individual color channels using the Photoshop command “External Channel”!