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Published on Oct 17, 2012
Your camera's apertures really live in the lens - not the camera. The aperture is an iris like the pupil of your eye that can be expanded and contracted to allow more or less light into the camera. A high number like f22 means you have a small aperture and a low number like f4 means you have a wide one. I know - it's back to front and very irritating.
So apertures are an exposure control. a bigger aperture lets in more light so you get a brighter picture, and a smaller one lets in less so you get a darker image. But there's actually a bit more to it.
Apertures (or f stops) are also a creative control too because they're the primary control for depth of field. A wide aperture means less depth in your photo and a small one means more. So how do you control exposure if adjusting apertures up and down for creative reasons is going to mess with the overall exposure of the image?
Well you have to choose the aperture you want for creative reasons, then adjust the shutter speed to compensate. There's a camera mode called aperture priority or aperture value (more on this at http://www.photographycourses.biz/ape...) depending on make of camera which lets you choose the aperture - and the camera selects a shutter speed it thinks will give you the correct exposure.