How to Edit your Pictures

Brigthness

Brightness is generally thought to be the simplest in concept. Just make the image brighter or darker by a specified amount, right? First we must distinguish between true brightness and something else called "gamma". Increasing gamma by moving a mid-tone slider on a histogram is not the same as increasing brightness. Increasing Gamma/mid-tones can make an image look brighter, but it is non-linear in that it only increases brightness of the shadows and mid-tones in an image without affecting the highlights. Traditional brightness on the other hand, simply brightens the entire image from the shadows to the highlights equally. Let's see what happens when we add some brightness to an image.

Contrast

Contrast is defined as the separation between the darkest and brightest areas of the image. Increase contrast and you increase the separation between dark and bright, making shadows darker and highlights brighter. Decrease contrast and you bring the shadows up and the highlights down to make them closer to one another. Adding contrast usually adds "pop" and makes an image look more vibrant while decreasing contrast can make an image look duller. Here is an example where we add some contrast.

Saturation

Saturation is similar to contrast, however instead of increasing the separation between shadows and highlights, we increase the separation between colors. An example showing increased saturation would show the same effect as figure 3 above for the red image but the B/W image would not change at all because B/W or gray detail has no saturation. As a result, an increase in saturation results in an increase in contrast, brightness, and sharpness on the red image as in figure 3 and no change to the B/W image. Again, a change in saturation normally has a more noticeable effect on vibrant colors and less on dull colors or colors that are almost neutral. This is because to change saturation, there must be some color saturation to work with in the first place.