How to photograph a document with a phone (properly)

A modern phone is a genuinely good document camera. It is also, in most people's hands, a machine for producing trapezoidal, unevenly lit images with the photographer's own shadow across the middle. The difference between those two outcomes is not the phone. It is about six minutes of technique, and it will do more for a restoration than any processing that happens afterwards.

The reason is simple: restoration recovers what survives in the capture. It cannot recover detail the camera never recorded. A sharp, evenly lit, square photograph gives the pipeline something to work with; a dim, skewed, shadowed one gives it a smaller and worse starting point, and no amount of cleverness downstream fully makes that back.

Light

• Use indirect daylight. A window with the document beside it, lit from the side, not directly under the glass - soft, even light is what you are after.
• Turn the flash off. It blows out foils, laminate and glossy paper, and it creates a hard hotspot dead centre where the detail usually matters most.
• Avoid overhead room lights directly above you. That is exactly where your own shadow comes from when you lean over the page.
• For embossed seals, coins or blind-stamped paper, use raking light: a single lamp low and to one side, so the relief casts its own shadow and becomes visible.

Position

• Get the camera parallel to the page, not at an angle. Stand over the document and shoot straight down rather than leaning across it, which throws the far edge into keystone.
• Fill the frame with the document, but keep all four edges visible with a margin around them. Edge detection needs to see where the page ends to correct its geometry.
• Do not use zoom. Move the phone physically closer instead; digital zoom throws away the very detail you are trying to capture.
• Steady the phone against something - a stack of books, a shelf edge, both elbows on the table. Camera shake costs more fine detail than almost any other single factor.

The document itself

Never force brittle or curled paper flat. You will crack it, and you do not need to - capture it as it lies and let curvature and keystone correction handle the geometry afterwards. Photograph bound books as an open spread rather than pressing the spine down onto the glass, which damages the binding and distorts the text near the gutter anyway.

If a page is folded, unfold it gently and let it settle under a light weight for a few minutes before capturing, rather than fighting it flat in the moment. A fold shadow breaks the shapes of letters that cross it, and a broken shape is much harder to restore than a faint one.

A thirty-second pre-flight checklist

1. 1Is the light even, with no hotspot and no shadow of me across the page?
2. 2Is the camera square to the document, with all four edges and a margin visible?
3. 3Am I close enough to fill the frame without zooming, and steady enough not to blur?
4. 4Have I got the reverse side too, if anything shows through?

Why this comes before everything else

It is tempting to treat capture as a formality and restoration as the real work. It is the other way round. A good capture of a badly damaged document can be restored beautifully. A bad capture of a pristine document just gives you a well-restored photograph of bad lighting. The six minutes at the start are the highest-leverage six minutes in the whole process.