5

Given that almost every parameter affecting exposure is an approximation - your 35mm lens may actually be 32mm or 37mm, ISO 400 may be ISO 417 or ISO 393 - it probably doesn't matter as much which number you use. You're not going to get an exact answer anyway...


2

F# is only accurate when focused at infinity, because the lens' stated focal length is only accurate when focused at infinity. Combine that with rounded focal lengths and F#'s, that DoF and hyperfocus (in particular) are about not focusing at infinity, and the fact that DoF isn't a fixed aspect of an image (especially if the composition will be changed in ...


2

Over the years I've done five. 400mm f6.3 M42 Tokina telephoto whose aperture mechanism was seized up, with some of its blades buckled. Pentax Takumar 55mm f1.8 M42 that someone must have treated with WD40 or similar before putting it on eBay. I only noticed when the internal lens surfaces adjacent to the aperture mechanism became coated with oil droplets ...


1

As any DoF definition is based on some "arbitrary" limit for the diameter of the circle of diffusion, it will only ever be a rough indicator. It's not the case that inside the DoF, everything is perfectly sharp, and exactly at the DoF border it immediately becomes unsharp, it's a continuous degradation. So, what limit will you apply? 10µm or 30µm? ...


1

TL;DR: NO. But for film, you can go smaller film for a given pupil size ie DoF. This increases apparent brightness though not improving detail or gathering more light. Better still, change film. There's this equivalence thingy in photography. It yields two important conclusions, namely no free photons and no free hyper-focus. Let me begin with the second ...


Only top voted, non community-wiki answers of a minimum length are eligible