Channel operations are called Calculations in English. In fact, the principle is very simple.
But before the actual explanation, let’s do some preparatory knowledge first.
I believe that as soon as you come into contact with PS, you will know that there is a Blend option for any operation of PS.
You may rarely use the Blend effect of the tool, but everyone should know about the layer Blend.
(?? Never come across the word Blend?) Blend means "mixed". For PS, layer Blend means "layer blending mode" in the Chinese version.
You can pay attention to the Mode "Mode" option on the layer panel. This option is actually to choose how the layer is blended with the layers below.
How many ways are there to mix it? What you see on the panel is actually missing two types. I have also posted a post explaining the mixed mode before, but unfortunately there are few readers so I will repost it here.
All available blending modes are listed below. Among them, Behind and Clear are unique blending modes of editing tools, but there are no two blending methods for layers. These specific definitions may be a bit boring, but that's okay - you can skip over to specific examples and then compare them to the definitions.
Normal
Normal mode is also the default mode. No blending occurs with other layers.
Dissolve
Dissolve mode. The pixel color produced by dissolve mode is derived from a random permutation of the upper and lower blend colors, related to the pixel's opacity.
Behind
Behind the scenes pattern. Only the transparent areas of the layer are edited. This mode is only effective when the layer's Lock Transparent Pixels (lock transparent area) is unchecked.
Clear
Clear mode. Any editing will make the pixels transparent. This mode has nothing to do with the color of the brush, only the parameters of the brush. This mode is effective for the shape tool (when the Fill Pixel option is checked), the paint bucket tool, the brush tool, the pencil tool, the fill command, and the stroke command.
Darken
Darkening mode. Examine the color information of each channel and the mixed pixel color, and select the darker one as the mixed result. Brighter pixels are replaced by darker pixels, while darker pixels remain unchanged.
Multiply
Multiply mode. Examine the color information in each channel and perform positive overlay processing on the underlying color. The principle is the same as the "subtractive color principle" in color mode. The color produced by such a mixture is always darker than the original. If it is multiplied with black, only black will be produced. Mixing with white will not have any effect on the original color.
Color Burn
Color burn mode. Darkening the color of the underlying layer is similar to Multiply, but the difference is that it increases the contrast of the underlying layer based on the color of the overlaid pixels. Mixing with white has no effect.
Linear Burn
Linear color burn mode. Also similar to Multiply, by lowering the brightness, the base color becomes darker to reflect the blended colors. Mixing with white has no effect.
Lighten
Brightening mode. Contrary to the darkening mode, the brightness of the mixed pixels is compared, and the lighter pixels in the mixed color are selected to be retained, while other darker pixels are replaced.
Screen
screen mode. Mix according to the "increased color mode" in the color mixing principle. That is, for screen modes, colors have an additive effect. For example, when red, green and blue all have a maximum value of 255, mixing in Screen mode will result in white with an RGB value of (255, 255, 255). On the contrary, black means 0. Therefore, mixing with black in this mode has no effect, but mixing with white will get the maximum RGB color white (RGB value is 255, 255, 255).
Color Dodge
Color dodge mode. Just the opposite of Color Burn, it reflects the mixed color by reducing the contrast and brightening the underlying color. Mixing with black has no effect.
Linear Dodge
Linear color dodge mode. Similar to Color Dodge mode. But you get a blended color by increasing the brightness to lighten the underlying color. Mixing with black has no effect.
Overlay
Overlay mode. Whether the pixels are Multiply or Screen blended depends on the underlying color. The colors will be blended, but the brightness detail in the highlights and shadows of the underlying color will be preserved.
Soft Light
Soft light mode. Whether to darken or brighten the screen color depends on the upper layer color information. The resulting effect is similar to casting a diffuse spotlight on the image. If the upper color (light source) is brighter than 50% gray, the bottom layer will be illuminated (lightened). If the brightness of the upper color (light source) is lower than 50% gray, the lower layer will become darker, as if it is burnt.
If you directly use black or white to mix, it can produce an obvious darkening or brightening effect, but it will not make the covered area pure black or pure white.
Hard Light
High light mode. Multiply or screen-blend the underlying color, depending on the color of the upper layer. The effect is like applying a strong spotlight to the image. If the brightness of the upper color (light source) is higher than 50% gray, the image will be illuminated, and the blending method is similar to Screen (screen mode). On the contrary, if the brightness is lower than 50% gray, the image will become darker, and the blending method will be similar to Multiply (multiply mode). This mode adds shadows to the image. If you mix pure black or pure white, the result will be pure black or pure white.
Vivid Light
Bright light mode. Adjust contrast to darken or lighten colors, depending on the color distribution of the underlying image. If the brightness of the upper color (light source) is higher than 50% gray, the image will be lowered in contrast and brightened; if the brightness of the upper color (light source) is lower than 50% gray, the image will be raised in contrast and darkened.
Linear Light
Linear light pattern. If the brightness of the upper color (light source) is higher than the neutral gray (50% gray), use the method of increasing the brightness to make the picture brighter, otherwise use the method of reducing the brightness to make the picture darker.
Pin Light
Fixed light pattern. Replace colors according to the upper layer's color distribution information. If the brightness of the upper color (light source) is higher than 50% gray, the pixels darker than the upper color will be replaced, while the lighter pixels will not change. If the brightness of the upper color (light source) is lower than 50% gray, pixels that are lighter than the upper color will be replaced, while pixels that are darker will not change.
Difference
Difference mode. According to the brightness distribution of the colors on the upper and lower sides, the color values of the upper and lower pixels are subtracted. For example, if you use the maximum value of white to perform the difference operation, you will get an inverse effect (the lower layer color is subtracted and the complement value is obtained), but if you use black, no change will occur (black has the lowest brightness, and the lower layer color is subtracted from the minimum color value 0, The result is the same as before).
Exclusion
Exclude pattern. Similar to Difference, but produces lower contrast. Likewise, mixing with pure white gives an inverted effect, while mixing with pure black leaves no change.
Hue
Hue mode. The parameters that determine the generated color include: the brightness and saturation of the underlying color, and the hue of the upper color.
Saturation
Saturation mode. The parameters that determine the generated color include: the lightness and hue of the underlying color, and the saturation of the upper color. Mixing in this mode with a color with 0 saturation (gray) produces no change.
Color
Shading mode. The parameters that determine the generated color include: the lightness of the underlying color, and the hue and saturation of the upper color. This mode preserves the grayscale details of the original image. This mode can be used to colorize black and white or desaturated images.
Luminosity
Luminance mode. The parameters that determine the generated color include: the hue and saturation of the underlying color, and the lightness of the upper color. The effect produced by this mode is just the opposite of the Color mode. It blends with the lower color according to the brightness distribution of the upper color.
There are two missing operation modes above, namely add and subtract. These two are too simple, so I won’t talk about them.
Many people ask what exactly a channel is. I answer here, the channel is nothing more than a 256-level grayscale image. Why can it be related to the constituency? This is because PS uses it to save selections. How to save? How to convert? ——In fact, it is just the grayscale value corresponding to the transparency of the selected area. This is another long story, and due to space limitations, I won’t go into it.
Where does the most intuitive grayscale impression of the channel come from? ——The channel panel. When you switch to the pass panel, what you see is a grayscale image.
Well, here comes the key to understanding calculation. PS emphasizes unity, and everything can be related to Blend. Tools such as brushes have Blend mode, layers also have Blend mode, and of course channels also have Blend mode. Why? Channels are also images!
Then it's easy to understand. Suppose there is such an operation: Multiply operation between channel 1 and channel 2, and then generate channel 3. How to understand?
-Multiply operation between channel 1 and channel 2, and then generate channel 3
-Multiply mix grayscale image 1 and grayscale image 2, and then copy them into grayscale image 3
Easy to understand, right? Practical operation?
You can try it and see if there is any difference between these two operations.
Here's a test:
1. Create a new grayscale document, fill the background with black, and use the white feathered edge brush to draw a few random strokes. Then create a new layer, fill it with black, and then use the white feathered edge brush to draw a few random strokes. In this way, we You will get two different layers of grayscale images.
2. Change the blending mode of the above layer to any one, such as Multiply. The effect you see now is produced by layer blending.
3. We want to save the merged results, what should we do? Ctrl+A selects all, then Ctrl+Shift+C, merge and copy, then Ctrl+D deselects, and pastes. The new layer obtained is the new layer mixed by Blend. Click the layer's eye icon to hide it.
4. Okay, let's go back to the passage. First, copy two different layers of grayscale images into the pass. Hide the upper layer, copy the background, then go to the channel panel, create a new alpha1, Ctrl+v, and paste the grayscale image into the channel. They are exactly the same.
5. Treat another grayscale image similarly, so that we get two channels, alpha1 and alpha2.
6. Select images->calculations, open the calculation dialog box, select source1 (source channel 1) as alpha1, source2 (source channel 22) as alpha2, and select the Blending (mixing/overlay) below that you just used Mode: Multiply, Result (result), of course select New Channel (new channel).
7. OK and see what the result is. The result is a new channel alpha3.
8. Please compare alpha3 and the grayscale layer just generated. Are there any differences? -The answer is of course the same.
It's not so abstract now. Actually that's not the case. In fact, I can get the same results by using layers to perform these operations, and for effect monitoring, it is indeed easier than channel operations. But the trouble is that in the end I have to copy the result into the channel to create a selection.