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
Discussion about cameras, lenses and photography in general.