A photograph can be that. But I think it's more accurate to say that an un-altered photograph is what a camera captured on some medium over some period of time. The time interval could be short or relatively long. A simple example: This weekend I plan to shoot a roll of 20 year old Ilford SFX 200 using a red filter. I have an idea of what the photographs might look like but it won't be what I saw, - at least I hope not. I expect that there will be some resemblance to what I saw and with some luck, at least one photography will look cool.