Start with the moment of submission. What will the form ask you to upload or hand over, and what exact checks can fail? Work backwards from those answers.
Do not repair everything at once
A rejected photo usually has a small number of failing conditions. Fixing all of them together makes it harder to know what actually worked.
Keep a copy of the version that failed
When troubleshooting, do not overwrite the previous file immediately. A simple filename such as passport-original.jpg, passport-size-fixed.jpg and passport-upload-version.jpg makes the workflow auditable and prevents accidental loss of the original.
Before the upload field
Open the exported file outside the editor, check its actual dimensions and size, and compare the portrait with the current official examples. Keep the original capture untouched in case the application needs a different version.
Why “passport size” is not one measurement
Different authorities use different physical sizes and face-position rules. A 35 × 45 mm output, a 50 × 70 mm output and a 51 × 51 mm output can all belong to legitimate passport or visa workflows. Start from the destination, not the nickname.
In FastIDPhoto, that means choosing the document profile before final export so the same original portrait can produce separate, traceable versions.
A note for this exact search
For this particular topic, save the final version with the destination and date in the filename. That makes a second application easier to prepare without guessing which export you used first.
How to Fix an Underexposed Passport Photo
Use the Studio after you have confirmed the requirement: upload or capture, prepare the image, then export the document-specific result.