Passport photographs aren't rocket science. According to the USA website giving information on passports the photographs do not need to be taken by a professional photographer but they certainly cannot be hand held selfies. I gave a link earlier to the part of the website that has a tool for sizing, positioning and cropping of a jpeg file so that it conforms.
Here is another
link that gives instructions on how to take the photograph. I note they say it must not be altered by editing but I have always done the normal adjustments to exposure, contrast, sharpening and WB if needed. In NZ we have a website you can upload the photograph to and you get a message back a short time later advising whether it conforms or not.
Richard have you had a look at the website that has the answers? It should be very useful.