First Check Which Route You're On
The ETA takes a live picture instead of a photo you bring.
South Africa now has two ways in, and only one of them wants a photograph from you. Everything else on this page describes the traditional visa, applied for at a mission or a VFS centre, where you hand over a 35x45mm print.
The other route is the Electronic Travel Authorisation. Its application does not accept a prepared file at all — you photograph your passport with your camera, then the biometrics step asks you to take a live picture of yourself inside the application, and the outcome comes back instantly.
This is worth knowing before you spend anything. If you are on the ETA route, a photo you made in advance has nowhere to go.
The ETA is limited, though: it covers tourism and visitor purposes, no work, and only if you land at O.R. Tambo, Cape Town International or Lanseria. Arriving anywhere else, or travelling for another purpose, puts you back on the visa route and back to the specification below.
