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"You can not produce two exposures that have the same focal length and f/ratio that have different depths of field." I am not sure why we are both establishing

"You can not produce two exposures that have the same focal length and f/ratio that have different depths of field." I am not sure why we are both establishing to one another that DoF is determined by the dispersion of the light hitting the film plane when we already know this. My Mamiya Sekor 50mm ƒ/6.3 has a DoF not even tangibly different from my Nikkor 50mm ƒ/1.4, unless I stop the latter down to ƒ/6.3 which produces two identical exposures at same ƒ/ratio but with very different DoF.

ajkessler 15y ago
This is simply not true. If you stop your Nikkor down to 6.3, it will have the identical depth of field as your Mamiya does at 6.3.
- eftpotrm 15y ago
  No; the larger sensor size of the Mamiya as a medium format camera will give less depth of field for a given aperture than the 35mm Nikon. Otherwise you're right, so in the odd circumstance the poster has a Nikkor 50/1.4 medium format or Mamiya small format 50/6.3 then their depth of field characteristics will be as you said. I'm also pretty sure that even on 6x7 50mm @ f/6.3 wouldn't give DoF characteristics anywhere near 50mm @ f/1.4 on a DX sensor (as the extreme examples to artificially push them closer together), and they'd have a radically different field of view.
  - ajkessler 15y ago
    Well yes, but we're talking all other things being equal.
ghshephard 15y ago
You aren't suggesting that your Sekor 50mm at F/6.3 has a DOF simliar to your Nikkor 50mm at F/1.4 for a subject at similar distances? A 50mm @ F/1.4 is a tight portrait lens, that frequently trips me up and ends up with a lot of unfocussed pictures (well, focussed on the Tip of a nose, or an ear-hair) - whereas a 50mm @ F/6.3 is in an entirely different story. I don't recall having too many out-of-focus pictures at F/6.3 on any of my 50mm lenses. Can you, perhaps, explains where you are getting your definition of "F-Stop?" Charitably, I'd like to believe you are just using a little known definition of the word, and I'd love to see your source material. I'm sure it will open my eyes to a different perspective on photography than what I've been operating with the last fifteen years.

ajkessler 15y ago

This is simply not true. If you stop your Nikkor down to 6.3, it will have the identical depth of field as your Mamiya does at 6.3.

eftpotrm 15y ago
No; the larger sensor size of the Mamiya as a medium format camera will give less depth of field for a given aperture than the 35mm Nikon. Otherwise you're right, so in the odd circumstance the poster has a Nikkor 50/1.4 medium format or Mamiya small format 50/6.3 then their depth of field characteristics will be as you said. I'm also pretty sure that even on 6x7 50mm @ f/6.3 wouldn't give DoF characteristics anywhere near 50mm @ f/1.4 on a DX sensor (as the extreme examples to artificially push them closer together), and they'd have a radically different field of view.
- ajkessler 15y ago
  Well yes, but we're talking all other things being equal.

ghshephard 15y ago

You aren't suggesting that your Sekor 50mm at F/6.3 has a DOF simliar to your Nikkor 50mm at F/1.4 for a subject at similar distances? A 50mm @ F/1.4 is a tight portrait lens, that frequently trips me up and ends up with a lot of unfocussed pictures (well, focussed on the Tip of a nose, or an ear-hair) - whereas a 50mm @ F/6.3 is in an entirely different story. I don't recall having too many out-of-focus pictures at F/6.3 on any of my 50mm lenses. Can you, perhaps, explains where you are getting your definition of "F-Stop?" Charitably, I'd like to believe you are just using a little known definition of the word, and I'd love to see your source material. I'm sure it will open my eyes to a different perspective on photography than what I've been operating with the last fifteen years.