| Joined: | Mon Apr 2nd, 2012 |
| Location: | South Lakeland, UK |
| Posts: | 4066 |
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Exposure? I keep seeing this word pop up in things I read, but I have yet to find out what it really means.
Exposure, in different contexts means different things...
An exposure, to take an image with the camera.
The sensor is like film, it records the image which is focused onto it while it is exposed, while the shutter is open.
Exposure duration, the shutter speed, the time the sensor is exposed to the image.
Exposure (settings) the combination of shutter speed and aperture.
Exposure *Stop*, means one step of the shutter speed, or one full step of the aperture.
Exposure Value, or EV is a way of altering the shutter speed up and the aperture down (or wider) both move by one stop each normally so for example 1/500 Sec at f8 is the same EV as 1/1000 Sec at f5.6 or 1/2000 at f4 or going the other way 1/250 Sec at f11.
I know next to nothing about music but the sounds of instruments double or halve in frequency with each sound value? with light it's much the same, I think? Not sure if that helps...
The reason for EV's is so you can open or close the aperture to get the depth of focus you want OR increase or reduce the shutter speed to get the exact speed effect you want, like blurring the spokes of a wheel to show movement or the propellor of an aircraft, to show movement, etc while retaining the same exposure value.
The exposure varies with the light. More light, needs less the exposure. Poor light may mean raising the ISO setting on the camera because the sensor just can't produce an image. BUT raising the ISO too much can cause what we call noise, this is electronic noise when the light isn't sufficient to produce an image the sensor tries to amplify the signal and that can cause noise in the form of gritty dots of multi colours. Not very nice.
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Robert.