Old and imperfect photographs
When the only photo you have is the only photo you have
A great many portraits here start from a photograph nobody would call good: a print from the nineties, a low-resolution phone picture from a decade ago, a frame pulled out of a video. These are often the most important photographs there are, because the subject is no longer here to be photographed again. They are worth trying.
If you are working from a paper print, photograph it flat in daylight rather than scanning it under a lamp — lay it on a table near a window, hold the camera parallel to it and step back far enough that your own shadow is out of the frame. Turn off the flash, which will otherwise bounce straight back off the print. A phone photo of a photo, taken this way, is usually better than a rushed scan.
Grain, faded colour, a crease across the corner, a scan that has gone slightly yellow — all of these are workable. Colour can be brought back, grain is not carried into the painted surface, and damage away from the face rarely matters. What cannot be recovered is detail that was never captured: a face lost in shadow, a face too small in the frame, or a face blurred by movement.
The honest answer, in every uncertain case, is to upload it and look. The preview costs nothing and tells you in a minute or two what no amount of guessing will. If it does not work, try a second photograph — or ask for the light and the crop to be changed, which is free.
Files
Practicalities
JPEG, PNG, HEIC and WebP all work. Send the original file rather than one that has been through a messaging app if you can — chat apps recompress images hard, and a photo that has been forwarded three times has lost detail that the original still has. Airdrop, email to yourself, or a cloud photo library will all preserve it.
Do not crop tightly before uploading; a little space around the subject gives more room to compose the portrait. Screenshots of photos are a last resort, as they capture the screen rather than the image. And avoid photos with heavy filters or beauty smoothing already applied — the portrait works from what is in the picture, and a filter has already thrown some of that away.
Try the photo you are unsure about
A minute of looking settles it better than an afternoon of deciding. The preview is free either way.