💡 Remove shadows, even out the lighting

Where scan shadows come from

Photograph a page on a desk and the physics is against you: the light comes from one lamp or window, and your phone, hand and body sit between it and the paper. The result is the signature look of a phone scan — a soft dark band across one edge, a gradient from bright to grey, sometimes the crisp outline of the phone itself.

The shadow is not on the paper; it is uneven illumination recorded by the camera. That is why it can be removed: the document underneath is uniformly white, so the unevenness is separable from the content printed on it.

How shadow removal works here

The document filter estimates the page’s background illumination and levels it, so regions that were dimmed by a shadow are lifted back to the same white as the rest of the sheet, while printed text keeps its contrast. It runs with the rest of the pipeline in your browser — the photo is not uploaded to be cleaned.

This is background correction, tuned for paper. It is not a general photo relighting tool: it will not remove the shadow a tree casts on a person, and it assumes the underlying page is a broadly uniform surface. On documents, that assumption is what makes the result look scanned instead of photographed.

What it handles well — and what it cannot

Soft, wide shadows — the common case — disappear almost completely. Text under the shadow stays legible because darkening reduced brightness, not information. Colour casts from warm indoor light are corrected by the same levelling, which is why deshadowed pages also stop looking yellow.

A hard shadow edge that falls exactly on dense print can leave a faint seam, and a photo that is genuinely underexposed — shot in a dark room at night — has real noise where detail should be, which no levelling can restore. If a page is badly lit, thirty seconds spent re-shooting it near a window beats any filter.

Avoiding the shadow at capture time

Removal exists because nobody photographs paper in a studio. But the cleanest scan is still the one whose photo needed the least rescuing.

• Put the light in front of you and the page, not behind you — your silhouette is the shadow.
• Shoot from directly above; a tilted phone stretches its own shadow across the sheet.
• Use daylight from a window when you can; one broad soft source beats two lamps.
• For a stack of pages, stand once, frame once, and keep the geometry for every sheet.