What the specification means in practice
This is the one specification on the site where the honest answer is "it depends on the consulate". The European Commission requires a photo compliant with ICAO standards and publishes a width of 35 to 40 mm with the face taking up 70% to 80% of the photograph. It does not publish a height. 35 × 45 mm is what the overwhelming majority of Schengen consulates ask for and what photo booths across Europe produce, but it is a convention rather than a figure written into the Visa Code.
Why consulates differ
A Schengen visa is issued by one member state on behalf of all of them, and each member state runs its own consular network with its own application guidance. Most converge on 35 × 45 mm. Some do not: Spanish consulates in the United States, for instance, ask for a 2 × 2 inch photo, matching the American convention their applicants are already used to.
The rule that follows from this is simple and worth more than any measurement on this page: find the guidance published by the consulate that will actually handle your application, and follow that. The country whose consulate you apply to is the one whose photo rules apply.
The parts that do not vary
Whatever the frame size, the Commission’s requirements hold everywhere. The photograph must be no more than six months old and must show your current appearance. Your face must take up 70% to 80% of the frame, measured chin to crown, in a close-up of the head and the top of the shoulders.
The background must be plain and light-coloured. Lighting must be uniform, with no shadows across the face or behind the head, no flash reflection on the skin, and no red eye. Skin tones must appear natural — a heavily colour-corrected or washed-out photo is refused.
Glasses are allowed, within limits
Unlike the United States, the Schengen standard permits glasses. The conditions are that your eyes are clearly visible, there is no flash reflection off the lenses, and the lenses are not tinted. The guidance also suggests avoiding heavy frames and wearing lighter ones if you have them, because frames must not cover any part of the eyes.
Head coverings are not permitted except for religious reasons, and where worn, the facial features from the bottom of the chin to the top of the forehead and both edges of the face must be clearly shown.
Framing and pose
You must face square on to the camera with both edges of your face visible — not a three-quarter portrait pose, and not tilted. Look directly at the lens with a neutral expression and your mouth closed. Nothing else may appear in the frame: no chair backs, no toys, no other people.
Standing too close to the camera is a specific named failure. So is standing too far away, which produces a face smaller than the 70% floor. About a metre and a half from the lens, with the photo cropped afterwards, gives a natural result at the right proportion.
Printing and attaching the photo
The photograph must be printed on high-quality photographic paper at high resolution. Ink marks, creases and pixellation are named rejection causes. Some consulates ask that the photo be glued to the application form rather than stapled, so that the image itself is not punctured — another detail worth checking in the consulate’s own instructions rather than assuming.