Brightness & contrast
Brightness and contrast sliders.
This runs in your browser. Nothing is uploaded.
About Brightness & contrast
Raises or lowers overall brightness and contrast with two sliders running from -100 to 100, working on the pixels in your browser so the photo never leaves your device.
Most photos that look wrong look wrong in an obvious way: the whole frame is too dark, or it's washed out and lifeless. Phone cameras metering for a bright window, documents shot under a desk lamp, a screenshot of a projector slide that came out grey. Two sliders fix a surprising number of those, which is why this is usually the first thing worth trying.
Brightness here is addition. The number you choose is added to the red, green and blue value of every pixel, so +30 moves a value of 100 to 130 and a value of 240 to its ceiling at 255. Contrast is a multiplication around mid-grey: values above 128 travel further up, values below travel further down, and 128 itself barely moves. Both controls start at 0.
Because both operations stop at 0 and 255, anything pushed past either end stays there. Brighten a photo that already has a bright sky and the sky turns into a flat white shape with nothing left in it. Drag contrast all the way to -100 and the multiplier reaches zero, collapsing the entire image into a single grey rectangle. Small moves, checked in the preview, beat one big one.
How to use Brightness & contrast
- 1Drop a photo onto the panel, or click it to browse your files.
- 2Move the Brightness and Contrast sliders, or type exact numbers into the boxes beside them.
- 3Click Apply preview to render the adjusted image.
- 4Click Download to save it as a PNG.
What it won't do
- Clipped highlights and crushed shadows cannot be brought back afterwards.
- One global adjustment for the whole frame — no masks, no selective areas.
- Both sliders treat red, green and blue identically, so neither will correct a colour cast.
Common questions
What's the difference between brightness and exposure?
Brightness adds a fixed amount to every pixel; exposure multiplies. Adding +40 lifts a dark pixel and a bright pixel by the same 40 levels, which raises the blacks to grey and flattens the picture. The exposure tool multiplies by two raised to the stops you pick, so shadows move a little and highlights move a lot — closer to how a camera behaves.
Why does raising contrast lose detail?
Contrast pushes values away from mid-grey, and anything landing above 255 or below 0 is clipped to those limits. Highlights merge into flat white, shadows into flat black, and once the file is saved that detail is gone. Watch the brightest and darkest parts of the preview rather than the middle, since the middle is where the damage never shows.
Why does contrast at -100 turn the whole image grey?
The contrast multiplier reaches zero at -100, so every pixel collapses onto the mid-grey pivot at 128. That's the mathematical end of the slider rather than a fault. Anything below roughly -70 already looks badly washed out, so almost every useful adjustment lives in a narrow band close to the centre.
Can I stack two colour adjustments in one pass?
No. Each time you click Apply preview the tool starts again from the image you loaded, so a second adjustment replaces the first rather than building on it. To combine two, download the result and drop that file back in. The download is a PNG, which is lossless, so nothing degrades on the round trip.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation