Adjust Image Brightness

Why a global brightness change is usually the wrong tool

A brightness adjustment shifts every pixel by the same amount, which fixes an image that is uniformly too dark or too light and damages one that is not. Raising the brightness of a photo that is only slightly underexposed pushes the highlights further into clipping, where the detail is already gone, and leaves the shadows no better. In most cases the right adjustment is exposure or contrast, which affects the midtones, rather than brightness, which shifts everything including the ends of the range.

NoteIf highlights are already white with no detail, raising brightness cannot recover them. Nothing can.

Clipping, and why it is irreversible

A pixel at 255 in any channel has no more information to give. Pushing brightness until the highlights reach 255 destroys information permanently, and no later adjustment can bring it back, which is why an over brightened sky or a face cannot be repaired. The same applies at the other end, where a pixel at 0 in every channel has lost all shadow detail. Working in an order that protects the ends of the range matters: get the exposure right before anything else.

• A pixel at full brightness has no headroom left.
• A pixel at pure black has no shadow detail left.
• Neither can be recovered by a later adjustment.
• Get the exposure right before making any other change.
• Check the histogram after each change if your tool shows one.

A better order of adjustments

A reliable sequence for a photo that needs correcting is exposure first, because it sets where the midtones sit, then contrast, which sets the range, then colour, and only then any local or creative adjustments. Brightness belongs in the exposure step rather than as a separate late adjustment, because applying it late tends to clip. Working in that order means fewer changes are needed, and the result looks like a correction rather than a series of fixes layered on top of each other.

• Step one: exposure, to place the midtones correctly.
• Step two: contrast, to set the tonal range.
• Step three: white balance and colour.
• Step four: saturation or vibrance, if it is needed.
• Keep brightness changes early, where they cannot clip the highlights.

Global versus local

A single global brightness change assumes the whole image needs the same correction, which is rarely true. Most photographs that need work have a correctly exposed subject and an underexposed background, or a backlit scene where the exposure has been set for the background. Those need a local adjustment, applied to part of the image, rather than a global one that makes the good areas worse. If the subject looks right and the rest does not, a global brightness change is the wrong tool entirely.

• Global adjustment: correct when the whole frame is exposed similarly.
• Local adjustment: correct when part of the frame needs a different exposure.
• Backlit scenes need local treatment on the subject.
• A global change cannot fix a mismatch between subject and background.
• If the subject is right, do not touch it with a global adjustment.

NoteA global brightness change applied to a well exposed subject is the most common way to make a photo worse.