Hong Kong passport photo

40 × 50 mm, with the head 32 to 36 mm tall from chin to top of hair.

The measurements

Photo size: 40 × 50 mm
Head height: 32 to 36 mm, chin to top of hair
Background: Plain white
As a digital file: 472 × 591 pixels at 300 dpi, or 945 × 1181 pixels at 600 dpi
Used for: HKSAR passport, ID card

Plain white background.

Consulates sometimes ask for something slightly different from the home country, so read the photo page of the office you are applying to before you print.

Taking the photo at home

Stand about 2 feet in front of a plain white wall.
Face a window, so the light is even and there is no shadow behind you.
Have someone hold the phone at eye level, 4 to 5 feet away.
Eyes open, mouth closed, looking straight at the camera. No glasses or hat.
Leave room around your head. The tool crops it to 40 × 50 mm.