Lens aperture

The aperture of a lens is its maximum opening. The bigger the aperture, the more light is gathered, and the less light you need to take a good photo. This is the most overlooked lens specification, but it very important, especially if you like to take photos indoors without flash or from a reasonable distance.

Lens aperture is measured in f/numbers, such as f/2.0 or f/3.5. An aperture of f/2.0 literally means that the lens opening is half the focal length of the lens. Thus, smaller numbers mean bigger lens openings. You would rather have a lens that is f/2.0 than a lens that is f/4.0.

I really like have a fast (large aperture) lens. It means I can shoot photos indoors without flash, and these look a lot more natural than flash photos. You can also take a lot of photos less obtrusively without a flash. Digital photographers tend to shoot a lot of photos, and you can drive people nuts if you shoot 20 flash photos in ten minutes. They will hardly notice your shooting these twenty shots with flash disabled, and you will get much better candids.

So, what is a good aperture? The answer is getting worse, not better. I would prefer not buy a camera with a slower lens than f/2.8. My favorites a few years ago were the Olympus C3040Z and C4040Z, with f/1.8 lenses. These days, you will have trouble finding a non-SLR camera with an f/1.8 lens. The best seems to be f/2.8 - f/3.5.

Note that cameras with zoom often have a range of maximum apertures listed, such as f/2.5 - f/4.0. This means the maximum aperture at the most wide angle setting is f/2.5, and the maximum aperture at the most telephoto setting is f/4.0.