aperture?

edge0freason · Sep 3, 2007

hey i just have a quick question. does aperture affect how dark or light a photo turns out? does it effect noise or other things? i just wasn't sure

Big Mike · Sep 3, 2007

The exposure of a photography is affected mainly by three things. The aperture (hole in the lens), the shutter speed (length of time for the exposure) and the sensitivity of the medium (ISO).

So you could say that yes, the aperture affects how light or dark a photo turns out...that is, if you change the aperture but don't change the other settings...the image will be lighter or darker. The same would be true of the shutter speed or ISO...if you change one, without changing something else, it will change the exposure.

What usually happens though, is that when you change the aperture, you (or the camera) changes the shutter speed to compensate. This way, you keep the proper exposure.

Now...why would we change the aperture? Firstly, aperture controls DOF (depth of field)...which is the depth of the area that will be in focus. A larger aperture (low F number) will give you a shallow DOF. A shallow DOF is good for things like outdoor portraits because you can have the subject in focus but the background blurry.

On the other side, if you use a small aperture (high F number), your DOF will be greater. This is good for things like landscape shots. You can get a close tree and distant mountains both to be in focus.

When you change the aperture to get the DOF you want...you also have to consider the shutter speed. If you use a small aperture to get more DOF...the shutter will have to be open longer in order to get the exposure. So for landscape shots with a small aperture, you will often need long shutter speeds. It is therefore recommended that you use a tripod, so that you don't get blurriness from camera shake.

sparris · Sep 6, 2007

does the F in "F number" mean Focus, Feild or something else?

JamesD · Sep 6, 2007

The f actually refers to focal length. Take, for example, a lens with a 50mm focal length, and a 25mm aperture.

You'll often this specified as f/2. It literally means, in our 50mm case, 50mm/2, or 25mm... which happens to be our actual aperture size.