How to scan a document with a webcam or phone camera

A flatbed scanner has an unfair advantage: a closed lid, even light, and paper pressed perfectly flat. A camera has none of that. The good news is that four things decide almost every camera scan, and all four are easy to fix once you know what to look for:light, angle, background, and focus.

1. Light: from the side, and plenty of it

The most common problem is your own shadow. If the lamp or window is behind you, your head and phone sit between the light and the page. Turn so the light falls on the paper from the side, or stand with the window in front of you and slightly to one side.

• Daylight beats a desk lamp. Near a window during the day gives soft, even light with no colour cast.
• Avoid the flash on glossy paper. It leaves a white hot spot right where the text is. Flash works on matte paper in a dark room, but daylight is still better.
• Watch for two-tone pages. If half the page is brighter than the other, the scan style will struggle to make the paper evenly white. Move until the light looks even.

2. Angle: straight above, or let the corners do the work

A photo taken at an angle makes the page look like a trapezoid: wide at the bottom, narrow at the top. Text far from the camera becomes smaller and blurrier. You have two options:

1. Hold the camera parallel to the page. On a phone, look for the moment the page edges look straight on screen.
2. Correct the corners afterwards. In Cam Scanner, drag the four corner handles to the four corners of the paper. The tool flattens the page as if it had been shot from straight above.

Corner correction fixes geometry, but not detail. If the far edge of the page was blurry in the photo, it stays blurry after flattening. So keep the angle modest, ideally less than about 30 degrees from straight above.

Using a laptop webcam

A webcam points at your face, not at the desk. The easiest trick is to hold the page up facing the screen, flat against a book or clipboard so it does not bend. Fill as much of the preview as you can, keep your fingers off the text, and capture. Then correct the corners. Webcams have lower resolution than phone cameras, so for small print, a phone photo added with Add images usually reads better.

3. Background: contrast makes edges easy

The scanner needs to see where the paper ends. White paper on a white desk is hard to separate, for software and for people. Put the page on something darker: a wooden table, a dark folder, or a notebook cover. Remove other papers from the frame so the edges are unambiguous.

4. Focus and stillness

• Tap to focus on the text, not the table. Wait a second for the image to settle before capturing.
• Brace your elbows on the table. Motion blur at the moment of capture is the second most common reason for unreadable scans.
• Fill the frame. The closer the page fills the image, the more pixels each letter gets.
• Wipe the lens. A phone lens with a fingerprint gives soft, hazy pictures that no filter can sharpen.

Choosing a scan style

Brightness and contrast sliders fine-tune the result. If text starts breaking into dots or thin lines disappear, you have pushed contrast too far.

A 20-second checklist before you send

1. Zoom in on the smallest text. Can you read every word?
2. Are all edges and corners of the page inside the scan?
3. Are the pages in the right order and the right way up?
4. Do numbers that matter, like amounts and dates, match the paper?