The larger the aperture opening/the more light/the easier it is to focus. The larger the aperture opening/the shallower the DOF/the easier to critically focus.
Which seems like it's the same thing, but it isn't really if you think about it. Also the aperture number is a ratio of the focal length over the diameter for example 1/2.8 * 50mm or 50/2.8 ~ 18mm diameter opening. 1/3.5 x 50mm or 50/3.5 ~ 14mm so the number you're looking at is actually larger... (but is in a short hand form where the 1 as numerator and focal length are "understood". You will sometimes see aperture expressed as 1:2.8 which is getting closer to the explicit truth. eric wrote: > Been looking at some wide angle lenses for my DL, and been noticing that > while any truly wide angle lense is awfully expensive (yeah, I know, > photography is an expensive hobby), the ones with big aperatures are > noticeably cheaper than those with small aperatures, numerically > speaking (i.e a 1:2.8 is more than one with 1:3.5). > > I know the aperature controls how much light enters the lens (along with > shutter speed), and a smaller aperature number means more light can > enter. Other than making it easier to get an in-focus picture while > hand holding the camera, what other reason would I want to get a smaller > number aperature? Considering 90%+ of my photography is done of > non-moving subjects, and using a tripod, can I compensate with a slower > shutter speed, or longer exposures? > > eric > > -- Entropy Seminar: The results of a five yeer studee ntu the sekend lw uf thurmodynamiks aand itz inevibl fxt hon shewb rt nslpn raq liot. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
