Some small reflections on DoF

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Erik Kaffehr
Erik Kaffehr Veteran Member • Posts: 5,825
Some small reflections on DoF
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Recent discussions got me a bit interested in perception of DoF.

DoF is essentially about what level of detail is perceived to be acceptably sharp. That level obviously depends on the viewing environment.

An image that is pretty out of focus can be perceived as sharp when looking at it at small enlargement.

Getting higher resolving devices, we may look at detail in much higher enlargement and that can make DoF very thin.

Previous year I experimented a bit with managing DoF. This image may be a good example:

The image here is downscaled to 1200 pixels height, while the inserts are actual pixels. Image was shot on 37x49 mm sensor with a Hasselblad Zeiss 180/4 Sonnar at f/16 focused at 35 m.

What I considered the main subject was the group of trees in the center (red insert) that was like 60m from shooting position.

I wanted the reeds be in reasonable focus, so they would not be distracting. The area marked in green was around 19 m away.

The forest in the background, I didn't care much about.

I used Lumariver DoF calculator. It uses two criteria for sharpness and takes diffraction into account.

  • Main subject was assigned sharp
  • Foreground was assigned soft

After that I tried to find a compromise...

I found that f/16 on 180 mm, focused at 35 m would yield a 'sharp' focus at 59 m and a 'soft' close focus at 20 m.

So, I tried to find something at 35 m to focus on.

Based on my previous experience, there would be a significant loss of sharpness at f/16, but that could be handled pretty well by sharpening.

Best regards

Erik

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Erik Kaffehr
Website: http://echophoto.dnsalias.net
Magic uses to disappear in controlled experiments…
Gallery: http://echophoto.smugmug.com
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