Adjust the Brightness, Contrast and Saturation of a Photo

How it works

Choose the photos in the box (tap or click), set the three sliders and press Apply. All three scales have their neutral point in the middle: at zero nothing changes, right increases, left decreases. Brightness is additive, meaning it adds a fixed amount to every colour channel: at +20, roughly 26 units are added on the 255 scale and a dark photo lifts as a whole. Contrast works around the mid-grey point of 128, pushing light pixels lighter and dark pixels darker; at +40 the factor is about 1.37 and at +100 it reaches 2.27. Saturation moves each channel towards or away from that pixel's own grey value: at -50 the colours fade by half, at -100 the photo drops to greyscale, and at +100 the colours become twice as vivid. Sepia is applied after all three adjustments and gives the photo the yellow of an old print. The transparency channel is never touched, so empty areas in a PNG stay empty.

This tool is also known as adjust image brightness contrast, photo saturation adjust, brighten a dark photo, increase contrast online, desaturate image, colour correct photo online, sepia filter photo.

What is Contrast?

Contrast is the distance between the lightest and the darkest tones in an image. In a low contrast photo every tone gathers near the middle and the picture looks hazy, as if seen through a grey veil; at high contrast the tones spread towards both ends, detail sharpens, and information starts to disappear at the extremes. Raising contrast is not the same as adding light: the overall brightness of the photo stays roughly the same and only the tones move away from mid grey. That is why trying to fix a hazy image with brightness fails — it makes the haze whiter.

What is Saturation?

Saturation describes how pure a colour is: at high saturation a colour holds its own hue strongly, at low saturation it drifts towards grey. The colour is not removed, it is mixed with grey. At the zero end of the scale all three channels reach the same value and the image drops to greyscale. Raising saturation is tempting but it crosses the line quickly on skin: in portraits, anything above +20 usually pulls faces towards orange. Landscapes and product shots tolerate far more, because pure colour is expected there.

What is Luma (brightness weighting)?

Luma reduces a colour to a single number describing how bright it appears to the eye, and it is not a plain average of the three channels. The eye is far more sensitive to green than to red, and more to red than to blue, so the weights are not shared equally. This tool uses the Rec. 709 weights: red 0.2126, green 0.7152, blue 0.0722. Saturation moves each channel towards or away from that value. With equal weights a yellow area would come out darker than it is and a blue one lighter than it is.

What is the difference between saturation at -100 and converting to black and white?

The results are close but not identical, and the difference is in the weights. Pulling saturation to -100 sets every channel to that pixel's Rec. 709 luma value, where green weighs 0.7152, red 0.2126 and blue 0.0722. The black and white tool uses the Rec. 601 weights instead (0.299 / 0.587 / 0.114), which give red a noticeably larger share. In the same photo a red rose comes out slightly darker in the greyscale produced here and slightly lighter over there. The practical choice is this: if greyscale is your actual goal, go to the black and white tool, because that page treats greyscale methods and the sepia option as its subject. Here greyscale is simply the far end of a correction scale, and this is the right place when the real job is balancing brightness, contrast and colour.

Clipped tones do not come back — brightness first, then contrast

Brightness and contrast are applied in that order, with a clamp in between: a pixel pushed past 255 by brightness is stopped there, and contrast is then applied to the stopped value. This is deliberate and it is how a real photo editor behaves. The consequence is simple: if you opened the brightness all the way and blew the sky out to pure white, lowering the contrast on the same screen will not bring it back. A pixel stuck at white holds no information any more.

So make your adjustments in small steps and always start from the original file. If you dislike a result, do not run a second pass over the output — go back to the source photo. A JPG output is re-encoded every time you save, and stacked losses become visible at some point.

The same logic applies downwards: pull brightness to -100 and crush the shadows to solid black, and the detail in those areas is gone as well.

Which slider fixes which problem?

The three controls solve three problems that look alike but are not. Naming the problem before you touch a slider is the shortest way to the right one.

A common mistake is trying to fix a hazy photo with brightness: raise it and the haze simply goes whiter. What a hazy image lacks is not light but separation, which is contrast.

• The whole photo is dark, shot in shade → Brightness +10 to +30
• The image looks hazy, as if behind a grey veil → Contrast +20 to +40
• The colours are washed out and lifeless → Saturation +20 to +40
• The colours are overdone, skin tones gone orange → Saturation -20 to -40
• A document or scan is hard to read → Brightness +10 and Contrast +40 together
• You want an aged photo look → Saturation -40 with sepia on

Transparency and batches

The adjustments are applied to the colour channels only; nothing is ever written to the transparency channel. If your PNG or WEBP has empty areas they stay empty in the output, and semi-transparent edges do not shift. A JPG source comes back as JPG, other formats as PNG, and the file name gets a -filtre suffix.

Pick several files and the same settings are applied to all of them. That is ideal for a series shot in one place, but photos taken under different light need separate passes, because the correction that suits one will blow out the next.

The result line lists which adjustments were applied, with their signs. If you touched no slider at all, it says so plainly.

Frequently asked questions

How do I brighten a dark photo?

Choose the photos, move the brightness slider to somewhere between +10 and +30 and press Apply. If the result still looks hazy, raise the contrast by about +20 as well; brightness on its own does not restore separation.

Does saturation at -100 make the photo black and white?

Yes, the result is greyscale. If greyscale is all you want, the black and white tool is the more direct route and it carries the sepia option too. This tool is built for colour correction, and greyscale is the far end of its scale.

Can the adjustments be undone?

Not from the output file: pixels pushed to pure white or pure black cannot be recovered. Your original file is untouched though — this tool writes a new copy. If you dislike the result, return to the source photo and try different settings.

Why does contrast work around 128?

128 is the middle of the 0 to 255 scale, that is, mid grey. Raising contrast means pushing lighter pixels up from that point and darker ones down. Put the centre anywhere else and raising contrast would also brighten or darken the whole photo.

Are my photos uploaded anywhere?

No. Everything happens inside your browser from the moment you pick a file. The image never reaches a server, and the tool keeps working even if the connection drops.