DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
JCB123
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Re: DotTune: Video Tutorial for AF tuning without photographs
In reply to Robin Casady, 6 months ago

Robin Casady wrote:

Horshack wrote:

Robin Casady wrote:

Thanks Horshack.

How much does the range vary? Instead of moving increment by increment can you take a jump to speed up finding the other end of the range?

It depends on the lens. On my Sigma 35mm f/1.4 the range is very small, only 4 AF tune units. On my 50G f/1.4 it's 9 tune units. You can jump around at any increment you'd like when trying to locate the general are of the range.

Thanks. Just out of curiosity, any idea what characteristic of the lens determines the range?

That would be anything that affects DOF. So for a given distance the focal length and the max aperture. We test at 50 x FL so the distance increases with focal length. Depth of field reduces with reduced distance so FL & distance tend to cancel (but not exactly) We also test wide open, so lenses with a fast max aperture will have shallower DOF. The shallower the DOF the smaller the range.

Heres a link to a DOF calculater - http://www.cambridgeincolour.com/tutorials/dof-calculator.htm

Regards

John

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