Guide
Photo and signature sizes for exam forms
Application portals reject more photographs than anything else on the form, and the error messages are rarely specific. This is what the requirements usually mean and how to satisfy all of them at once.
Read the specification as four separate constraints
A typical instruction reads something like: recent colour photograph, 3.5 × 4.5 cm, JPEG format, between 20 KB and 50 KB. That is four independent requirements and people usually only notice two of them.
- Dimensions. Sometimes in pixels, sometimes in centimetres. If given in centimetres, the portal almost always still checks pixels, and you have to guess the DPI it assumed. 300 DPI is the safe assumption, which makes 3.5 × 4.5 cm about 413 × 531 pixels.
- File size. Often both a floor and a ceiling. The floor exists to stop people uploading a thumbnail; the ceiling to protect storage.
- Format. Nearly always JPEG. A PNG renamed to .jpg will be rejected by anything that inspects the file rather than the extension, which is most systems.
- Content. Plain background, face filling most of the frame, no sunglasses. No tool can fix this one for you.
The order that works
Crop first, resize second, compress last. This matters because each step changes the input to the next one, and doing them in the wrong order means going back to the start.
Crop to the right proportions with crop image, choosing the ratio rather than trying to be exact. Then set the pixel dimensions with resize in pixels. Only then bring the bytes down with the compressor that matches your limit, most often 50 KB or 20 KB. Both of those have an option to hold the dimensions fixed, which is exactly what you want here: the pixel size is already correct and must not change.
When you cannot hit the floor
A small photograph at modest quality can easily land below a 20 KB minimum, and there is nothing you can do to the picture to make it bigger without making it worse. This is what increase image size in KB is for. Its padding mode adds inert bytes to the file without touching a single pixel, so the image is identical and the file clears the floor. Validators read the byte count, and the byte count is now right.
The signature
Signatures are usually specified much smaller, often 140 × 60 pixels and under 20 KB, and they are almost always photographed rather than scanned. Two things help enormously: sign in black or dark blue ink on plain white unlined paper, and photograph it in flat daylight rather than under a lamp, which throws a shadow diagonally across the page. Crop tightly, leave a thin white margin, and resize.
Common failure messages
| Invalid file type | The file is not really a JPEG. Re-save it properly with convert to JPG rather than renaming it. |
|---|---|
| File too large | Compress, holding the dimensions locked. |
| File too small | Pad it, do not enlarge the picture. |
| Incorrect dimensions | The portal wants exact pixels. Resize to the stated numbers precisely, not approximately. |
| Upload failed, no reason | Often a stale session rather than the file. Log in again before assuming the photograph is at fault. |
Before you submit
Keep the original photograph. Every compression pass is destructive, so if the portal changes its mind about the limits, you want to start again from the camera file rather than from something that has already been through the mill three times.