Guide · Updated 29 July 2026 · Reading time 7 minutes

Scan Settings That Actually Matter

Scanning apps and machines offer a wall of options — resolution, colour mode, quality, enhancement, format. Most of them barely change the result. Three of them decide almost everything. This guide covers the three that matter, so your scans come out readable, right-sized and fit for whatever you need them for.

1. Resolution — the one you cannot fix later

Resolution is how much detail the scan captures, usually measured in DPI (dots per inch) for flatbed scanners, or simply in pixels for a phone. It is the single most important setting because it is the only one you cannot improve afterwards. Capture too little detail and it is gone — enlarging the scan later just magnifies blur; it invents no new information.

Around 300 DPI is the practical standard for document text. It is sharp enough to read comfortably and to run OCR on, without bloating the file.
Below ~200 DPI, small letters like e, c and o start blurring together, and recognition accuracy drops fast.
Above 300–400 DPI rarely helps an ordinary document — it mostly makes the file bigger. Reserve high resolution for fine detail, photographs or artwork.

On a phone, the equivalent of "enough resolution" is simply filling the frame with the page. A page photographed edge-to-edge has plenty of detail; the same page shot from far away, sitting small in the middle of the frame, does not — no matter how many megapixels the camera claims.

If you will run OCR or ever print the document, err on the side of more resolution at capture. It is the one decision you cannot walk back.

2. Colour mode — colour, grey, or black & white

This controls how each pixel's tone is stored, and it is really a trade between fidelity and file size.

Mode	Keeps	File size	Best for
Colour	Everything — ink colour, stamps, photos	Largest	Documents with coloured seals, signatures, highlighting or images
Greyscale	Shades of grey, no colour	Medium	Plain text where you want smooth, natural-looking pages
Black & white	Pure black or white, nothing between	Smallest	Crisp printed text you will photocopy or fax

The trap: black & white looks fantastic on clean printed text and disastrous on anything pale or pictorial. It forces every pixel to one extreme, so a light-coloured photo, a faint pencil note or a pastel illustration collapses into black blobs or vanishes entirely. If a page has any coloured picture, a seal or faint writing, do not use pure black & white — use Colour or Grey.

3. Enhancement — cleaning up the lighting

Enhancement corrects the unevenness a camera introduces: a bright hotspot under a lamp, a shadow across one corner, the dull grey cast of a page shot in poor light. Done well, it makes a phone photo look like a proper scan — white paper, even tone, readable text. In Pennary the camera scanner offers a few enhance modes; here is when each earns its place:

Original — no processing, the true camera colour. Best when the lighting was already good and colour fidelity matters most.
Auto — evens out lighting and lifts colour while keeping it faithful. The best all-round default: it cleans the background to white and keeps blue ink, red stamps and coloured pictures looking right. This is the mode to reach for on most documents.
Grey — the same lighting correction without colour, for smaller, tidy greyscale pages.
Black & white — maximum crispness for plain text, with the caveats above. Use it deliberately, per page, not as a default.

A washed-out scan is usually a lighting problem, not a settings problem. Before hunting through modes, move to side lighting from a window and reshoot — it fixes more than any slider.

Putting it together

For the vast majority of everyday documents, the winning combination is simple:

Fill the frame with the page (your resolution).
Use Auto enhance — clean background, faithful colour.
Straighten and crop to the page edges before you save.

Switch to Grey or Black & White only when you specifically want a smaller file for plain text, and only per page — never let a black & white choice silently carry over onto a colour page, or you will turn a photo into a smudge.

What about file size?

File size is a result of the three settings above, not a separate dial to fight. A colour scan at high resolution is large because it is holding a lot of detail. If a file is too big to send, the honest fixes are: scan plain-text pages in Grey, keep resolution sensible rather than maximal, or compress the finished PDF — in that order. Cranking every setting to maximum "just in case" is how a ten-page document becomes an un-emailable 60 MB file.