A phone camera is good enough for an official passport photo if the lighting and background are set up correctly - no studio equipment required.
Stand about 60 cm in front of a flat, unmarked wall. It does not need to be white - any plain, light-colored surface works, since the exact background color can be corrected afterward.
Face a window during daytime so light falls evenly on the face. Avoid direct sunlight, which creates harsh shadows, and avoid overhead lighting alone, which shadows the eyes.
Hold the phone (or prop it up) at the same height as your eyes, roughly 1.2 to 1.5 metres away, and use the timer or ask someone else to take the photo to avoid camera shake.
Look directly at the camera with a neutral expression, mouth closed, both eyes open. Hair should be pushed back enough that it does not cover the face.
The raw photo from the previous steps is rarely the right size or background on its own. Upload it to Upass, choose the destination country, and the crop guide and background color are applied automatically before downloading the final JPG or PDF.