Lensbusters.com

There are two competing variables in making a properly exposed negative (actually three I guess if you count film speed.) But if you're just getting started with film photography you may have heard of reciprocity as it pertains to exposure. By the way reciprocity should not be mistaken for a shortening of reciprocity failure as I often hear people mis-speak. Reciprocity is the relationship between the length of time of an exposure and the light coming in through the lens controlled by the aperture. In theory, (and usually in practice) doubling the time of an exposure and halfing the light coming in will result the exact same density negative or transparency. For example, if you meter (or using the " Sunny 16" rule ) an exposure as say f16 at 1/125th , your negs would be exposed* exactly the same as if you used: f32 @ 1/30th f22 @ 1/60th f16 @ 1/125th f11 @ 1/250th f8 @ 1/500th f5.6 @ 1/1000th Note I said exposed exactly the same , not look exactly the

When I first started photographing, as a teenager in the early 1980's literally everybody used a film camera. All sorts of films, color and black and white could be purchased from convenience stores, drug stores, supermarkets, by mail order, or most likely at one of the ubiquitous One Hour Photo shops. You could get Disc film , 110 , 127 , 120 , 220 , and sheet film locally in San Jose where I grew up, as well as in most any city of a certain size. For those of you just getting in to photography, you might find the notion of metering light for exposure difficult. Your iPhone's camera not only do a great job of metering and exposing, but you also have the advantage of being able to instantly see the results and correct if needed. But in the century plus of history where film was king, there were a lot of tricks folks came up with to make exposure easy. Back in the 1980's there would typically be a small sheet of paper folded up in the film box with a bunch of information