Scan enhancement explained: what “cleanup” actually does

“Enhanced” can mean anything from subtle to cartoon. Good document enhancement has a specific goal: make the page look like it was scanned on a flatbed — evenly lit, clean paper, crisp ink — without lying about the content.

Measure first, touch second

ToPDF starts by measuring the cropped page: how uneven is the illumination? how bright is the paper tone? how flat is the contrast? how soft is the detail? Each treatment is then applied in proportion to need — a well-shot page passes almost untouched; a dim, shadow-striped one gets the full course. That's why results look natural across wildly different photos.

The treatments

• Illumination flattening: the page's lighting field is estimated and divided out — soft shadows and vignettes disappear, paper becomes uniform. (The star of shadow removal.)
• Adaptive brightening: genuinely dim pages are lifted until paper reads as paper — capped so nothing blows out.
• Local contrast: flat, faint print gets region-by-region contrast so pale corners and strong centres both land right.
• Measured sharpening: only as much as the page's softness calls for — no crunchy halos on already-sharp text.

What it deliberately doesn’t do

No content edits, no beautification, no binarised black-and-white smashing (colour stamps and photos survive), no AI redrawing of glyphs. For documents that might be checked or archived, “faithful but clean” is the only defensible standard — the same normalisation a photocopier performs, done better.

Frequently asked questions

Can enhancement ever make a page worse?

The proportional design exists to prevent that — minimal need, minimal touch. Pathological inputs (extreme noise, heavy glare) mostly pass through with modest gains rather than aggressive artefacts.

Why does my scan look better than the original paper?

Age-yellowing and ambient gloom live in the illumination layer, which gets flattened. The ink was always that crisp — now the paper matches it.