How to set white balance on a white sheet (custom white balance)?

Firstly, why: in order to correctly shoot a wedding photo booths nyc with white balance for specific conditions (for example, if the room is lit by daylight from the outside, an incandescent lamp on the table and fluorescent lamps on the ceiling), it makes sense mainly for JPEG, because then it’s harder to fix. Secondly, it is easy to do: shoot a frame with a predominance of something neutral and not too dark (white sheet, white reflector, gray background, gray test card, asphalt, office gray ceiling), but preferably closer to the object, then choose the appropriate menu item (“custom wb”, “custom wb”) and specify this test frame there. You need to specify before shooting, not after. There are more advanced cameras: the quick setting function of the WB is displayed on a quick button with the ability to turn it on (seen in the Samsung NX10 and Olympus PEN), by pressing it, you will see a changed viewfinder on the screen with the command – aim at the target, press the shutter button – the camera takes a test frame, without writing to the matrix and measures the BB on it, for this it is enough just to find a more or less gray or white surface. You can play with the white balance by giving the camera not white samples, but color ones, so that later you can shoot with a knocked down BB to get interesting shades, although this can also be done when editing or converting.