The electricity requirement has an interesting side effect in that it is an aid in distinguishing genuine photographs from other pictures which look like photographs but might not be.

The only energy input required to generate a photograph in a sensitive surface is light. Photography was invented in, and works perfectly in, a world without electricity. Other processes which can make fine looking pictures, ink-jet for example, cannot be done, even in principle, if there is no electricity.

Of course, light alone is not sufficient for the entire cycle of production. The picture maker needs energy too but in some of the workshops I have been to beer, pizza, and cigarettes seemed enough.