Usability of Zone Focusing

Started Oct 22, 2020 | Questions thread
Gerry Winterbourne Forum Pro • Posts: 19,063
Re: Usability of Zone Focusing

Gurusathiy wrote:

DeathArrow wrote:

I can't see how auto focus can be slow for static scenes such as landscapes.

My problem is when my friend enters the scene, auto-focus takes time to lock focus on my friend while my other friend snaps up easily in his mobile. That is the reason i told "slow".

If you have studied DOF you will realise that for the same picture the DOF gets deeper as the sensor gets smaller. Phone sensors are so small that DOF is almost infinite; but small sensors have other limitations - one always has to choose which limitations to accept.

It mostly means using a small aperture for a larger DoF, focusing at a distance and shooting when the photographer guesses the subject is near that distance. It doesn't give the best results.

This is exactly my issue, I want best results and hence the query to understand from experienced people on how they do it.

You should now know how to use a DOF calculator. Enter the details of your camera, lens and settings. Decide the nearest distance you want to be sharp, then adjust the aperture and focus distance until the calculator shows this as the near end of DOF and infinity as the far end. Then set the focus ring on your lens to the focus distance shown.

As long as focus is manual everything in the range calculated will be acceptably sharp, subject to the fact that DOF calculations make a number of assumptions so they are never perfectly accurate. But unless your critical object is exactly at the nearest distance that won't matter.

There are other methods; here's a klong but interesting read http://trenholm.org/hmmerk/download.html

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Gerry
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I'm happy for anyone to edit any of my photos and display the results
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First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne
gerry.winterbourne@ntlworld.com

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