View Single Post

Old 03-02-2019   #34
markbakovic
Registered User
 
markbakovic is offline
Join Date: Jan 2019
Location: Sydney
Posts: 36
Quote:
Originally Posted by ptpdprinter View Post
As if any of this makes much difference in the real world. You never heard any of these concerns about comparative diffraction between FF and MF film shooters. Perhaps someone can post some images illustrating this problem.
You did but the language was usually different.

First bit of this might help:
http://spiff.rit.edu/classes/phys312...elescopes.html

Fast lenses are less likely to achieve the diffraction limit. The theoretical resolution of a large format and kleinbild lens may be the same, but for the same field of view and manufacturing tolerances a longer lens is more likely to achieve that (or some % of that) performance.

Also: since f# determines resolution at the detector independent of focal length imaging a scene with a 50mm f.8 lens and a 150mm f.8 lens produce spots the same size (if they're both perfect). However, the aperture of one lens is ~6mm, while the other's is ~18mm, so each spot covers and area of the scene one third as big from the LF "normal" 150. If your grain/pixels are small enough to sample the spots correctly you get 3x the detail in the big format "at the same field of view". Another way of looking at it is you could stop down further and lose no detail in the scene, while making smaller spots on your detector (to take advantage of fine grain emulsion, say).
It might just be easier to think that at the same grain/pixel size, more of them across the frame translates to more of them across a given detail in the scene (think similar triangles with a given angle).

It's all muddied somewhat in digital land because 5 micron pixels have been around for ages, yet resolution has gone up... but when you think about Bayer masks and microlenses you realise quoted pixel sizes tell you the relative light gathering power, not how big a spot they can sample.
  Reply With Quote