To understand exposure compensation, first you need to understand what is a "stop". Each stop will allow half or double the light entering the camera. So eg, at f/5.6, one stop down will be at f/8 (remember higher f-value = smaller aperture), and at f/8 the light is half of that at f/5.6. Same goes for shutter speed. 1/250s allows only half the light comparing to 1/125s.Originally posted by revenant
oh ya, what's exposure compensation? those -1 , 0, +1
Eg. aperture values are number as: 2.8, 4, 5.6, 8, 11, 16, etc. Each step is a stop. Similarly, for shutter speed: 1/30, 1/60, 1/125, 1/250 etc. and each is a stop difference.
Now note this: f/5.6 at 1/125s = f/8 at 1/60s. Get it? In terms of aperture, you have 1 stop less light, but in terms of shutter speed, you have 1 stop more, so the end result is that the exposure is the same. Try this with your camera, chose a scene with constant lighting, then set your camera to aperture priority and change the f-stop, meter the scene and you can see what I just mentioned. You can do the same with shutter priority.
Each stop = 1EV, so 1 stop down = -1EV (less light), and 1 stop up = +1EV (more light). One easy way to remember this: + = more light, - = less light.
So what is exposure compensation? It is simply to deviate from the camera's metered exposure value. For example, if in aperture priority mode and your camera metering says the exposure is f/5.6 at 1/250s, setting a -1EV compensation will make the camera set the exposure value at f/5.6 at 1/500s (remember, less light). Note that most modern cameras allow you to set 1/3 compensation.
Hope that helps.