Question for Great Bustard

Started 3 months ago | Discussions thread
nigelht Senior Member • Posts: 1,449
Re: Even-handed description

Richard Butler wrote:

PhotoTeach2 wrote:

It is f/2,8 for exposure "setting", (SS), purposes but f/12.3 for DOF consideration.

This is a misleading simplification. Shot from the same position and with the results viewed at the same size:

Equivalent focal lengths and matched exposure settings give you:

  • The same field of view
  • The same image brightness
  • Different depth of field
  • Different levels of diffraction
  • Different levels of noise (since the images were made with different numbers of photons available)
  • The same exposure data in the EXIF

Equivalent focal length, aperture and whatever ISO is necessary will give:

  • The same field of view
  • The same image brightness
  • The same depth of field
  • The same level of differaction
  • Very similar levels of noise (since the images are made with the same number of photons available, shot noise notwithstanding)
  • Different EXIF values

So, the following statements are true:

f/2.8 from a light per unit area perspective, but the equivalent of f/12.3 on full frame from a total light perspective.

Or

f/12.3 for DOF consideration, F2.8 for EXIF matching purposes.

If we're going to trivialize and downplay one, it's only fair to do the same to the other.

Richard - dpreview.com

For a photography site to say that one should trivialize and downplay exposure is amusing.

f2.8 is not for EXIF matching purposes.  f2.8 is for capturing the image properly exposed in the lighting condition and the desired shutter speed.

This assertion that f-number is just for EXIF matching ignores that folks buy f2.8 lenses for more than a shallow DoF.

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