Question

How long has photography as we know it existed?

Answer 1

The answer to this is subjective I suppose. The Chinese philosopher Mo Ti discovered the concept of the camera obscura (pinhole camera) in the 5th century B.C., but the first recorded instance of projecting pinhole camera light on something photo-sensitive to make a permanent image is attributed to scientist Sir David Brewster in 1850. My vote goes to Brewster. Technically recording the camera obscura to a permanent image would be considered the first real "photograph".

It's rumored Leonardo Da Vinci, who extensively experimented with camera obcura, also found ways of developing pinhole camera light into images. This would put the date to around the late 1400's.