Adjust Image Contrast

What contrast changes

Contrast is the difference between the lightest and darkest parts of an image, and increasing it pushes the bright areas brighter and the dark areas darker at the same time. That is why it is the correct tool for a flat, hazy, or low contrast photograph, and the wrong tool for one that is merely underexposed. A flat image lacks tonal separation, so contrast restores it. A dark image has separation but the whole range is sitting too low, so exposure is what moves it.

Why extreme contrast looks bad

Once the range reaches the edges of what the format can hold, there is nowhere left to go. Bright areas clip to pure white and lose their texture, dark areas crush to pure black and lose their detail, and the result looks harsh and processed rather than clear. It is also unrecoverable in the same way brightness is: a pixel that has reached 0 or 255 has no more information, and no later adjustment will restore it. Moderate contrast, checked on a histogram, keeps the range inside what the format holds.

• Push contrast until highlights reach pure white and detail is gone.
• Push it further and shadows crush to black and lose texture too.
• Neither is recoverable with a later adjustment.
• Keep the range inside the format limits rather than at the edges.
• Check a histogram if the tool provides one.

NoteContrast is the most common adjustment to overdo, and overdoing it is permanent.

Global contrast versus local clarity

A global contrast change affects the whole image equally, which is right when the whole frame is flat. A local clarity adjustment, which is effectively a local contrast change, is a different tool and is what makes a subject stand out from its surroundings without flattening the rest of the frame. It is a more sophisticated operation and it is easy to overuse, because pushed too hard it produces an unnatural crunchy look with haloes around edges. Moderate local contrast is one of the most effective corrections available to a photograph.

• Global contrast for a uniformly flat image.
• Local clarity to separate a subject from its surroundings.
• Local contrast pushes too hard produce crunchy haloes around edges.
• Global and local are different tools answering different problems.

NoteA global contrast change cannot separate a subject. That needs a local adjustment.

Working in the right order

Contrast before brightness is the more sensible order, because it establishes where the tonal range sits before anything shifts the whole thing. Adjusting brightness first and contrast second tends to leave the image with the range against one edge of the format, which then limits what the contrast adjustment can do. The reliable sequence is exposure, then white balance, then contrast, then colour, and then any local work. Each step sets up the next rather than fighting it.

• Exposure first, to place the range correctly.
• White balance second, so contrast is not amplifying a colour cast.
• Contrast third, to expand the range without clipping.
• Saturation last, so increased contrast does not exaggerate colour.
• Keep the adjustments modest and check after each one.