Q.G.
Member
Again, to add more value to this discussion, we need to define what is meant by 'photograph'. I sense that some participants think of print, image, negative or the process of photographing when they mention 'photograph'. This confuses things.
Trying to decide what a photograph is will confuse things even more.
And we all already know what a photograph is well enough to discuss the question about when it comes about: no more complicated than a thing you look at that is created by the action of light. Any more detail is unnecessary.
Once you start singleing different thingies, different steps in the process, out as "the photograph" you find youself in a terrible pickle, needing to explain what the other bits involved then are. Something you will not be able to do.
And it doesn't make any difference anyway.
You can't ignore the "why" something (say, a negative) comes to be. This "why" (whatever it is) preceeds the clicking of shutters, the souping of bits of acetate with a sticky residue on it in chemicals, or whatever other step in the process you may want to single out.
Nobody suddenly finds him- or herself holding a camera pointed at something, or with film in a tank that is about to be filled with liquids, or whatever else you may like to consider as the "defining stage of a photograph", without ever having done anything beforehand to wind up in the situation.
So better not go that route. Forget about the impossible and useless definition.