Do you need a photograph at all?
For most applicants the answer is no, and almost nobody says so.
The Passport Seva instruction booklet is explicit: a photograph is not required for applications submitted at a Passport Seva Kendra (PSK) or a Post Office Passport Seva Kendra (POPSK). Your photograph is captured at the counter during your appointment. If you booked a PSK or POPSK appointment, you can skip the photo studio entirely.
A printed photograph is required only when you submit through a different collection centre — a District Passport Cell (DPC), an authorised Speed Post Centre (SPC), or a Citizen Service Centre (CSC) such as Bangalore One, e-Seva or e-Sampark. In those cases you paste one colour photograph into the box printed on the application form.
Separately from all of this, the online application flow now asks you to upload a photograph and a signature to the portal before the application is accepted. That upload is a digital file with its own rules, and it is what most people are actually looking for when they search for an Indian passport photo size.