Photo Editor

What each slider actually does

Exposure works the way a camera does: it multiplies the light in the scene. The calculation happens in linear light — the photo's values are converted out of the sRGB gamma curve, multiplied by two to the power of the exposure in stops, and converted back — so +1 EV genuinely doubles the light, highlights brighten faster than shadows, and the result looks like a longer exposure rather than a grey wash.

Brightness is a midtone curve. Pure black stays black and pure white stays white, so nothing clips; the middle of the range is lifted or lowered. Use it when a photo looks dim but its brightest parts are already bright. Contrast is an S-curve around mid-grey: it pushes darker-than-middle tones darker and lighter ones lighter, using the standard contrast factor 259(C + 255) / 255(259 − C).

Saturation scales how far each colour sits from grey, using the same matrix the CSS saturate() filter defines. Vibrance does the same but weights the change by how muted each pixel already is, so dull colours gain the most and already-vivid ones — skin, a red jacket — barely move. That is why vibrance is the safer of the two for portraits.

Warmth and tint are a white-balance correction. Warmth trades blue for red, which fixes the cold cast of shade and overcast light or the orange cast of indoor bulbs in the other direction; tint trades green for magenta, which fixes the green cast of some fluorescent and LED lighting. Hue rotates every colour around the colour wheel and is more of an effect than a correction.

Sharpening, blur and vignette

Sharpen is an unsharp mask, a technique borrowed from the darkroom: the photo is blurred, the blur is subtracted from the original to isolate the edges, and a proportion of those edges is added back. Flat areas are untouched because there the photo and its blur are the same. A little sharpening makes a phone photo look crisper; too much produces bright halos along edges and turns skin to sandpaper. Judge it at 100% zoom, not on a thumbnail.

Blur is a Gaussian blur, approximated with three fast box-blur passes — mathematically close enough that the difference is invisible, and fast enough to stay interactive. Its radius is a fraction of the photo's size, so the preview and the full-resolution export look the same. For hiding a face or a number plate, use the blur and pixelate tool instead: it works on a region, and its page explains why a mild blur is the weakest way to hide anything.

Vignette darkens towards the corners with a smooth fall-off, drawing the eye to the centre. A light vignette (10–25) flatters most portraits and landscapes; heavier settings are a stylistic choice.

Why this editor gives the same result in every browser

Many browser-based editors apply their adjustments with the canvas filter property — a single line of code that hands the work to the browser. Safari has never implemented that property. It accepts the line and silently draws the photo unchanged, so the sliders move and nothing happens, on every iPhone and iPad.

This editor computes every adjustment itself, pixel by pixel, in a fixed order: tone (exposure, white balance, brightness, contrast), vibrance, saturation and hue, black and white, sepia, invert, blur, sharpen, vignette. Because the arithmetic is the page's own, Chrome, Firefox and Safari produce the same numbers. The fixed order also means the result never depends on which slider you happened to move first.

The live preview works on a copy of up to 1,000 pixels across so the sliders respond instantly. Save runs the same calculation on the full-resolution photo. Every setting that depends on size — blur radius, sharpening radius, vignette shape — is defined relative to the image, so the saved file matches the preview.

A sensible order for editing a photo

Fix the light first. Set exposure so the important part of the picture is correctly bright, then use brightness for the midtones and contrast for punch. Fix colour next: warmth and tint until whites look white, then a modest amount of vibrance. Sharpen last, and lightly.

Use the before/after compare often. The eye adapts within seconds to an over-saturated or over-sharpened image and starts to read it as normal; flicking back to the original resets that and shows what you have really done. If the edit only looks better side by side but not on its own, it has probably gone too far.

The looks are starting points, not final answers. Vivid adds contrast and vibrance; Warm and Cool shift white balance; Matte lowers contrast and saturation for a flatter, editorial feel; Dramatic and Noir add contrast and vignette; Vintage blends in sepia. Pick one and then adjust the sliders — the look only sets their values.

Saving, and what this is not

JPEG is the right format for photographs, at quality 85–95. PNG is lossless and much larger for photos, but right for screenshots and graphics. WebP is smaller than JPEG at the same quality in browsers that can write it; Safari cannot, and the page saves a PNG instead and says so. Saving re-encodes the image, which removes its EXIF metadata — camera details, date and GPS location.

Your original file is never changed. The edit is a new file, so you can always go back.

This is an adjustments editor, not a replacement for Lightroom or Photoshop. There are no layers, masks or local adjustments, no healing or clone tool, no per-channel curves and no RAW support; work happens at 8 bits per channel, the same depth as the JPEG you started from. Very large photos are scaled to the largest canvas the browser allows — about 16.7 megapixels on iPhones — and the page tells you when that happens.