Adjust shadows, midtones and highlights separately with tone curves.
Adjust Shadows and Highlights with Tone Curves
Brightness sliders move a whole photo at once. Tone curves let you move the shadows, the midtones, and the highlights separately, which is far more powerful. This tool gives you that control in your browser: an S-curve control, a gamma control, and separate shadow and highlight lifts. Your photo never leaves your device. Nothing is uploaded, stored, or seen by anyone else, and the result downloads as a PNG.
Think of a tone curve as a map. Every brightness level in the original photo goes in one end, and a new brightness comes out the other. A straight diagonal line means no change. Bend the line into an S and dark tones get darker while bright tones get brighter, which adds contrast. Bend it the other way and contrast falls. The sliders in this tool shape that map without you having to draw it by hand.
The Four Controls
S-curve strength is the contrast control. Positive values deepen shadows and brighten highlights, which makes photos look punchier. Negative values flatten the curve, which softens harsh contrast in photos taken in strong sun. Thirty percent is a good starting point for most photos; beyond sixty the effect starts to look dramatic.
Gamma changes the midtones more than the ends. A gamma above one hundred darkens the middle of the range, which suits washed-out photos. Below one hundred it lifts the middle, which helps dark indoor shots. Gamma is the gentlest way to fix a photo that looks grey overall without crushing the shadows or blowing the highlights.
Shadows lift raises only the dark end of the range. It rescues detail in dark corners, under hats, and inside rooms seen through windows, without touching the bright sky. Highlights gain does the mirror job at the bright end, adding sparkle to skies and water. Used together, they let you rescue both ends of a high-contrast scene.
Using the Tool
Choose a photo, set the four sliders, and press apply. Compare with the original button before downloading. Toggle back and forth and look at three places: the darkest shadows, the main subject, and the brightest highlights. A good curve improves all three. If any one area looks worse, pull that control back.
Work in small steps. Move one slider at a time and watch the preview. It is tempting to push everything at once, but combined moves hide which control caused a problem. The classic beginner error is a strong S-curve plus a shadow lift plus a highlight gain, which produces a photo that is simultaneously contrasty and washed out.
Photos That Benefit Most
High-contrast scenes benefit most: a person against a bright window, a landscape with dark foreground and bright sky, or a street scene in harsh sun. These photos have information at both ends that a single brightness slider cannot reach. Curves reach each end separately.
Flat, grey photos benefit too, in the opposite direction. A photo taken on an overcast day often has all its tones squeezed into the middle. A moderate S-curve spreads them out again, restoring the depth the dull light removed. Old scanned photos, which often look faded, respond the same way.
Mistakes to Avoid
The most common mistake is crushing the blacks. Pushing shadows down until dark areas become pure black loses all detail there, and no later edit can bring it back. Watch the darkest parts of the preview. If texture disappears into solid black, ease off. The same applies at the bright end: blown highlights turn to featureless white.
Another mistake is judging the curve on a dim screen. A photo adjusted on a dark phone screen at night will look different in daylight. If the photo matters, check it at normal brightness before downloading. And always keep the original file. Curves are easy to redo, but only if the unedited photo still exists.
The tool is free, needs no account, and works on phones, tablets, and computers. Upload a photo, shape the curve with the four sliders, compare with the original, and download the result. Your photo stays on your device from start to finish.
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