Spread a flat or murky photo across the full tonal range automatically. Global for an even fix, adaptive to rescue dark corners and bright skies, with a strength slider to keep it natural.
Builds a histogram of the picture’s brightness, works out where the tones are bunched up, and remaps them so they are spread evenly from black to white. Colour ratios are preserved, so a red stays the same red, only lighter or darker. Global mode uses one histogram for the whole image. Adaptive mode splits the image into tiles, equalizes each tile with a clip limit that stops noise being amplified, and so lifts detail locally, in the manner of the CLAHE method used in medical and astronomy imaging.
A 4000 × 3000 photo taken through a dirty train window: everything sits between brightness 70 and 180, nothing is truly black or white, and it looks like it was shot through fog. Global equalization at 100 percent spreads that 110-value range across all 256, the haze disappears and the histogram in Image Histogram goes from a narrow hump to a full spread. At 100 percent the sky looks over-processed, so 65 percent is the keeper. The same image in Adaptive mode with 128 px tiles also brings out the seats in the dark foreground that Global left muddy.
Use it on hazy, foggy, underexposed or scanned images that lack punch, on old prints, and on scientific or document images where you want every detail visible. It is not a beautifier: correctly exposed photos gain nothing and often look worse, and portraits usually prefer a gentle Change Contrast instead. If only one region needs the treatment, Equalize Image Area limits it to a rectangle and feathers the edge; if the image is simply too dark overall, Change Exposure is the simpler fix.
Global is predictable and even; Adaptive is stronger and more local. Tile size in Adaptive mode sets how local: 32 px reacts to small features and can exaggerate noise on flat areas, 128 to 256 px behaves like a gentle version of Global. Strength blends the result with the original and is the control to reach for whenever the result looks too much. Output Same keeps the original format.
How is this different from raising the contrast? Contrast stretches all tones by the same amount. Equalization looks at how many pixels sit at each brightness and spreads the crowded ranges out most, so a photo that is mostly dark gets its shadows opened up while the few highlights barely move.
Why does my portrait look harsh? Full equalization pushes every tone towards an even spread, which exaggerates skin texture and blotches. Lower Strength to 40 to 60 percent, or use Adaptive with a large tile size, which is gentler on faces.
When should I pick Adaptive? When one part of the picture is far darker or brighter than the rest, such as a room interior with a window. Adaptive equalizes each tile on its own, so the window and the room both gain detail instead of one being sacrificed for the other.
Does the photo get uploaded? No. The histogram is computed and applied in your browser; nothing leaves your device.