Before using it, let’s briefly introduce the principle of the curve tool. Photoshop roughly divides images into three parts: dark tones, midtones, and highlights.
like this image
Picture: Material
Contrast effect:
Figure: Comparison effect You can use the "Decolor" command to convert the color image into a grayscale image to see the distribution of light and dark. You can see that the sky is high-light, the trees and the grass are dark.
Picture: color removal The two endpoints of the straight line in the Curves panel represent the highlight and shadow areas of the image respectively. The rest of the straight line is collectively called the midtones
Figure: Curve adjustment
Both endpoints can be adjusted separately
The following two animations demonstrate the effect of changing the shadow points and highlight points separately. The result is that the shadow or highlight parts are brightened or darkened.
Figure: The effect of changing the dark points individually
Pick up~
Figure: The effect of changing the highlight points
Changing the midtones can brighten or darken the overall image (click in the line to create a drag point) but the contrast between light and dark does not change (unlike the brightness increase of a TV). At the same time, the color saturation is also increased, which can be used to simulate the effect of natural ambient light intensity.
Figure: The effect of changing the midtones Appropriately lower the shadows and raise the highlights
Image: Reduce the dark tone
Can obtain images with a strong contrast between light and dark (so-called high contrast)
Figure: The resulting high-contrast image
However, doing so may cause image details in brighter areas to be lost (such as clouds in the sky), and this is not consistent with natural phenomena. At this point, you can create realistic natural landscapes by changing the midtones
Image: Changing midtones
This way the image will look more natural and there will be no obvious traces of alteration.
Effect Previously we made adjustments in the overall image, now let’s take a look at the effect of adjusting the channels individually. The images produced by electronic devices are composed of three colors of red, green, and blue light mixed in different proportions (if you look closely at a color TV screen, you will see countless small red, green, and blue dots. The same is true for computer monitors, but they are more detailed. ).
In other words, the images displayed on the screen are actually a mixture of three separate color images (red, green, blue) (just like a cocktail, although it is wine as a whole, is actually a mixture of multiple ingredients The so-called channel refers to the separate red, green and blue parts, also called RGB. If we brighten the red channel alone, it is equivalent to increasing the red component of the entire image, and the entire image will appear reddish; if we darken the red channel alone, the resulting image will appear cyan.
Cyan and red are inverse colors (also known as complementary colors), as are pink and green, yellow and blue. Inverted colors have a trade-off relationship with each other:
To lighten yellow, darken blue
To lighten pink, darken green
To lighten golden color (golden color is composed of red and yellow), you need to lighten red and darken blue at the same time
Now we need to change the color of the sky to golden. Since the sky belongs to the highlight area, we need to brighten the highlight part of the red channel.
Figure: Select the red channel
Also darkens the highlights of the blue channel
Figure: Adjusting the blue channel highlight
This way we get a golden sky effect
Figure: Result
Although this effect is gorgeous, if you look closely, the green mountains in the distance also turn yellow. The mountains should be part of the midtones, so we keep the midtones where they are in the red and blue channels.
Figure: Continue to adjust