Identity photos have this particularity: they are often mediocre, not always flattering... and we have to live with it for 5 to 10 years. Some regret it every time they have to show someone their driver's license or ID card.
However, this is a relatively simple exercise to do yourself, at home. The advantage is that you can do it several times until you get the ideal portrait. Here are some simple tips to achieve this. All you will need is a camera with a flash, ideally a cobra flash. A second flash may be a plus for more advanced configurations. We will also make sure to have a reflector, or failing that, a reflective white surface (white cardboard, board for markers, etc.).
Finally, more importantly, it will be necessary to find a clear plain background, but not white, this background color being prohibited by the administration. Finally prohibited... concerning white the thing is quite obscure (no pun intended) since the sites of certain administrations still consider the white background as permitted (Spanish embassies abroad for example), while the site service-public.com explicitly describes it as prohibited. In short... if in doubt, a quick phone call to the administration, or the choice of a gray background seems to be essential. This background will be a wall, or failing that, a piece of cardboard of the right color that will be placed behind the subject. The cardboard does not need to cover the entire field of the image; it is enough that it covers the area on which we will reframe at the end of the process. That is, mainly behind the head and shoulders.
Needless to say, the guidelines regarding the validity of passport photos must be strictly adhered to. The latter are listed on this page for papers issued by the Spanish administration. Other countries do not have the same criteria. Some allow the white background, others ask for a darker blue background than in Spain, some require the ears to be visible, etc. In short, remember to check all the details with the administrations concerned.
Extract from the sample PDF of photos accepted and refused by the Spanish administration.
Make way for practice
Sit your subject in front of the selected background. Don't glue it to the bottom, but leave some space in between. At least 50 cm... just to avoid any unattractive cast shadow of the subject on the background.
On the knees of the subject, we will place the reflector (real commercial reflector or sheet of material capable of reflecting the light) in order to erase the unsightly shadows under the nose, the eyes, and the chin. It's a cheap way to get an ersatz clamshell light that's frequently used in the studio and perfect for lighting a face nicely. Of course if you have several flashes you can replace the reflector with a second light... but very honestly, for such a small photo, the ceiling flash + reflector solution will often be more than enough.
Ideally, the camera will be placed on a tripod, at eye level with the subject's face. The cobra flash will be tilted backwards if you have a wall behind you, or towards the ceiling otherwise. The flash settings will then depend on your habits and the room you are in. Doing a few preliminary tests on a still and docile subject (a stuffed animal will do) can help find the right settings. In a room lit by a standard ceiling light with a Nikon cobra flash, you can put yourself in TTL-BL mode so that the flash tries to properly expose the subject and the background. To use this mode, it is essential to be able to measure matrix exposure. As for the optics, we will close to f/4 or f/5,6, that's enough. All at a sensitivity allowing good lighting of the scene... indoors and with this configuration, 400 ISO is often a comfortable threshold. Some prefer to shoot by setting themselves on the synchronization speed of their flash (1/200 s or 1/250 s), and others finally swear by natural lighting. It is difficult to draw up a standard map of the settings, which vary according to the material and the part used.
Which is also possible, provided that the light is intense enough (for the reflector to be useful), but too direct to avoid too high-contrast renderings. If necessary, a thin white curtain will be used to filter the sunlight.
In any case, it is difficult to give a precise setting, since all this depends on the room you are in, its lighting and the way in which its walls will reflect the light of the cobra flash. In short, use a familiar environment or take the time to take a few adjustment shots before you start.
A classic photo booth with children: fun photos, but unusable!
Last point before editing: do not hesitate to take a lot of photos. You are not in a photo booth and each additional view will not be charged. So experiment and choose the best photo for your papers.
Finally, it remains to edit the pictures. In Photoshop, you can easily resize the photo by first setting the size to 35 x 45 mm (via the Size menu in the working area), then adjusting the size of the face in the frame to the correct dimensions. To achieve this, all you have to do is draw ruler marks in order to properly control the size of the face, which must measure between 32 to 36 mm (i.e. 70 to 80% of the surface of the image), this going from the bottom of the chin at the top of the head (not counting the hair).
Finally, importantly, the eye area materialized in the capture of the PDF examples above represents a 10 mm high strip going from 13 mm to 23 mm from the top of the photo. Drawing precise marks on your image in Photoshop will help you to position the subject's face and eyes correctly and to adjust the dimensions appropriately.
Now it's time to print... and put together your file.