- [[Aperture and Depth of Field]] - [[Apertures - Maximum and Minimum]] Along with [[Shutter Speed]] and [[ISO]], the aperture is part of the *[[Exposure]] triangle*. It's the size of the hole in the lens that light passes through. Make the hole bigger, more light gets in. Double the size of the hole, but leave everything else the same, the image will get twice as bright. Double the hole, and halve the time the shutter is open, you get the same exposure, but you do still get a slightly different image. Beyond getting the exposure you want, the main effect of aperture is to get the [[Depth of Field]] you want. It's basically just how much of your image is in focus, and just how blurry those background bits are if you want that [[Bokeh]]. - Want everything in focus, as you tend to see with [[Camera Phone]] shots, and most [[Street Photography]]? Narrow aperture, or big number. f/8 usually gets a lot in focus, but it depends on your focal length and how far away things are. - Want the sort of portrait photo where the background is all blurry and the person seems to *pop* out of the image? Shallow depth of field, so you want a big aperture, or a *small* number. f/1.4 perhaps, if your lens can do it, or f/2.8. Again, depends on other things too.