What on earth is a stop? apart from the place you catch a bus? in photographic terms a stop is just a word which describes a halving or a doubling of the level of light. let me show you something, this is my venerable old mumia which i
used to use in the pre digital age, i’m going to use this because the principles the same plus i can take it apart to show you things. Let’s say for example I’ve set a shutter speed of one second, it looks like this, the shutter opens an amount of light comes in, the shutter closes. If i want to increase my exposure by one
stop there by letting in twice as much light i need to have the shutter open for twice as long, so i go from one second to two seconds, long old exposure. Works the other way too, if i want to decrease my exposure by
one-stop there by halving the amount of light, i go from one second to half a second, like this. You get the idea, that was only open for a short time you can also change your exposure by using your apertures which are known as f stops, some what confusingly, don’t get hung up by the names and numbers of these f stops, because they don’t really relate to halves and doubles. just don’t get hung up on it when you
look in the top of your dslr you’ll see a little f in front of the aperture
number on dslr’s they don’t necessarily halve and double, some may go in quarters but the principle is the same, as you increase the aperture, more stops of light come in, watch. That hole there is f eight, now if i wanted to reduce my exposure i would need to make that hole half the size, so half as much light goes in. I go from f eight to f eleven. That little movement actually halved the size of the hole so half as much light came in. I can go the other way too, if i wanted to increase the exposure by one stop i go from f eight to five six, like that. Now twice as much light is coming in, there are other things to do with stops
for example i know from experience that standing here in the shade there’s two stops less light on me than there would be over there in the sunshine, if i go and stand over there and Jane doesn’t change the exposure on her camera for me i’m going to get completely burned out. Watch this. i’m completely overexposed washed out, there’s two stops more light here than there is over there, that means it’s four times
brighter here because don’t forget your doubling two stops is four times brighter. Let’s come back into the normal stuff, so all i can say to you is don’t get too hung up, it’s just a term, it’s just a way of describing something. A stop is a halving or doubling of light.