Brightness & Contrast

About Brightness & Contrast

This tool adjusts brightness, contrast and saturation with three sliders that each run from minus 100 to plus 100. It suits underexposed snapshots, flat scans and washed-out screenshots that need a quick lift. Changes are recalculated after a short pause as you drag, so the preview stays close to what you will download.

How to use it

1. Drop your image in. The three sliders start at 0, which leaves it unchanged.
2. Drag Brightness to lighten or darken every pixel.
3. Adjust Contrast to spread or squeeze the tones around the middle gray.
4. Move Saturation up to intensify colors or down toward black and white.
5. Press Reset to return everything to 0, then Download the PNG when the result looks right.

What contrast plus 50 does

Contrast +50, brightness and saturation 0; a channel value of 100 and another of 200

The multiplier is about 1.48 around the midpoint 128, so 100 becomes about 86 and 200 becomes about 235. Darks get darker and lights get lighter.

When to use it

• Rescuing a photo taken in dim light so the subject is visible.
• Adding punch to a flat document scan before printing.
• Toning down oversaturated product photos to look more natural.
• Preparing a screenshot for a slide with slightly higher contrast for projectors.

Questions about Brightness & Contrast

How is brightness applied?

Each red, green and blue value is shifted by 2.55 times the slider number, so plus 20 adds 51 levels. Values are clamped at 0 and 255, and anything pushed past white cannot be recovered later.

What formula controls contrast?

It uses the classic factor 259 times contrast plus 255, divided by 255 times 259 minus contrast, applied around 128. Positive values stretch the range, negative values compress it toward gray.

What does the Saturation slider do at the extremes?

It moves each color toward or away from its own luminance. At minus 100 the picture is fully gray, and at plus 100 the color difference is doubled, which can clip bright colors.

Why is my highlight detail gone?

Raising brightness pushes light areas to pure white, and that information is discarded permanently in the output. Lower the brightness or use less contrast, and keep your original file.

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