| Brightness Filters
Reducing Brightness Let's take a look at the brightness filter. This image has had the brightness reduced by 50 percent. |
Notice how all the information has been shifted to the left. This is what the brightness filter does. It shifts ALL information in your image one way or another depending on the setting. In this case, the information that was in the shadows has now been bunched together. Again you lose detail. Here is what happens. Suppose you have some detail in the shadows. When you darken the image, you lower the luminosity value of all the pixels. Now, if you had a pixel with a value of 0 (black) and another with a value of 25 (dark blue, for instance) and you darken the image by a value of 35, the blue pixel will become black. Now there is no difference between these two pixels, and since the detail is contained in this difference, you lose detail.
Increasing Brightness This image has been brightened by 50 percent. |
You see the same effect occurs except to the other end of the spectrum. In this case, you would lose detail in the highlights, and for the same reasons. You are removing the differences between the lightest pixels in your image. I mentioned this in the Perception section, but I want to emphasize this. Your eyes are much more sensitive to mid-tones and highlights than shadows. Any excesses in these areas will be more readily apparent and objectionable than those in the shadows. Keep this in mind.
For these reasons, I do not use, nor do I recommend using, the brightness and contrast filters. There are some instances where you might use them, but there are other filters that you can use to correct these problems that are not destructive and give you much more control. Both the brightness and the contrast can be adjusted with the Levels filter (CTRL+L) or better yet, use the curves tool (CTRL+M) in Photoshop, and the Highlight/Mid-tone/Shadow (SHIFT+M) and Gamma (SHIFT+G) filters in Paint Shop Pro. You are much better off studying and using these filters, rather than brightness/contrast.
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