Focus question and advice please!

Started 2 months ago | Questions thread
Erik Kaffehr
Erik Kaffehr Senior Member • Posts: 2,768
Jim's plot a bit annotated...


  • Distance scale is logarithmic. Left side = 1m, right side = 1000m focus point 30 m
  • Diffraction is shown as red circle and defocus (CoC) is shown as green circle corresponding images added. These calculations are approximate and use 4.8 microns.
  • The grid shown is the pixel spacing.

Jim's plots show some interesting things. One is that stopping down can handle background well. Jim focused at 30 m and that is near hyperfocal distance for CoC = 0.010 mm and f/16. The diffusion spot will be around 0.012 mm from focus point. Stopping down further will not help background sharpness.

The parts near the camera, that is a few meters, can never be really sharp.

Best regards


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Erik Kaffehr
Magic uses to disappear in controlled experiments…

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