What is a stop?
Many Many people have asked us what a 'photography stop' is and when I was learning stops puzled the hell out of me for a while.
To be honest there's not much to them - the word 'stop' in photography is really a term for halving or doubling the exposure.You can increase or decrease your exposure and a 'Stop' is the jargon for doing it.
When you hear phrases like. "I opened it up a stop." All they're saying is they gave a shot more exposure. The term opened it up would suggest they did it by increasing the size of the aperture. But you could also do it by extending the shutter speed too.
This video explains what that means and how to do it in practical terms. Photography stop explained and demonstrated, Changing 'stops' with the shutter, Changing 'stops' with aperture and light levels and 'photography stops' in the environment.