How to prepare files for printing, so the result matches your screen

The gap between what you see on screen and what comes out of the printer has ordinary, predictable causes. Here they are, in order of how often they come up.

1. Aspect ratio, not resolution

Phones usually shoot at 4:3, and some modes at 16:9. Print formats are different: 10×15 cm is 2:3, and 13×18 cm is roughly 3:4. When the proportions do not match, something has to give — either the image is cropped or white bands appear. If you have a frame where someone's head is right against the top edge, tell us how you want it cropped, otherwise we make the call.

2. Colour space

Send files in sRGB. It is what photo labs and ordinary screens are calibrated for. A file saved in Adobe RGB or ProPhoto RGB and sent without an embedded profile comes out washed out, with greens and reds gone flat. If you do not know which space you are using, it is almost certainly sRGB and that is fine.

3. Format and compression

• JPEG at maximum quality, or TIFF, are the safe choices.
• Do not re-save the same JPEG repeatedly — each save adds loss on top of the last.
• HEIC from an iPhone is fine, but tell us so we convert it properly.
• PNG suits graphics and text, not photographs: a large file with no gain in quality.

4. Screen brightness

This is the cause behind “it came out too dark”. A phone at full brightness emits light; paper only reflects it. A photo edited at night on a screen turned all the way up will almost certainly print too dark. Check the photo on a screen at medium brightness, in a normally lit room, before ordering.

Do not upscale the file yourself before sending it. Send the original at its true resolution — enlargement done with the right tools, at printing time, gives a better result.