People who asked this used to say it was when light made a picture all by itself. It seemed a funny sort of thing when you consider that the early operators had so much to do. Even into the film era there was a great deal of mechanics, chemistry, and expense to get light to do something – it could not really have been considered to be doing it alone.
And then there were the retouchists…the photographers who smoothed and cleaned the world to cozen it into buying a better opinion of itself than ever came from a sunbeam. They used pencils, knives, brushes, shaking tables, graphite power, and paints to make Victorian and Edwardian portrait sitters look less frightful. They practically never succeeded.
Is a photo when the little electronic sensor sees light and makes a digital signal on a microscopic scale on a magnetic card? Stare at the SD card and tell me.
Is it when that card lets a signal out to a computer that lights up a phosphor screen in front of the eye? Maybe, but then press the little “x” on the upper left corner of the picture and it isn’t.
Is it in a cloud signal? A hard drive disc? Or is it only a photograph when it is a series of inkdots sprayed onto shiny paper?
Is it only really a photograph when it is published? Or awarded a club ribbon?
If a photograph falls over in a forest and there is no-one there to see it, did it really happen?
Ask Schroedinger’s cat.