How to take a China visa photo with your phone
The Chinese format is 33×48 mm, and it is the narrowest of the common visa sizes — two millimetres slimmer than the Schengen rectangle and three taller. Inside it the head measures 28–33 mm from the chin to the crown and 15–22 mm across, which is the detail that makes this photo different from every other one on this site: most authorities only tell you how tall the head has to be, so a crop that satisfies the height can still be refused for a face that sits too wide in a narrow frame.
That is an argument for shooting from further away rather than closer. Stand about two metres from a plain white wall and let the crop bring you in; a phone held at arm's length stretches the nose and widens the cheeks, and in a 33 mm frame that shows. Keep the phone at your eye level, use the rear camera, and face a window so the light arrives from the front. Both ears have to be visible, so tie long hair back behind the shoulders before the first shot rather than trying to fix it later.
Why a China visa photo comes back
Glasses are not accepted. This is stricter than the European rule about glare — there is no "as long as there is no reflection" version of it, so take them off, and give your eyes a moment to settle before the shot if you wear lenses all day.
The background must be plain white. Not off-white, not the light grey a British or German photo allows, and not a white wall that has picked up a colour cast from a warm lamp. The rest is standard: a neutral expression with the mouth closed, no head covering unless it is worn for religious reasons and the face stays fully visible, and colour — a black and white photo is refused outright.
Where a China visa photo is used
The same photo goes into the online application form and is normally printed and attached to the paper form you take to the visa application centre, so produce both a digital file and a print at 300 DPI. Tourist, business, student and family visit categories share the format. Check the current requirements for your category with the official Chinese visa application service site before you submit.