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 Originally Posted by Ian C
On page 17 of the Kodak Retina 1b manual (First version PDF), the last example gives a 22-foot hyperfocal distance at f/8. You have to read it carefully to see that this is the actual focusing distance being used (“The depth of field then extends from 11 feet to infinity.”)
This leads to a circle of confusion diameter of 0.047mm.
The Kodak Professional Photoguide, 1st Edition, 1975 says "Technically, the circle-of-confusion size used to calculate the depth of fields for each situation is about 1/1000 of the focal length of the normal lens for each format". So your 0.047mm figure is about what I'd expect Kodak to recommend.
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To add to the confusion about DOF, if one assumes the vision standard of 20/20 vision, even the manufacturer standard for CofC leads to overly generous DOF zone sizes, and a person with 20/20 vision would really NOT consider all of the out-of-focus zone to be 'acceptably sharp'. That is why many of us long ago had adopted the practice of looking at the DOF scale corresponding to an aperture value which was ONE LARGER than what was selected on the lens, for the DOF scale references....i.e. use f/5.6 marks on DOF scale when the lens aperture was f/8
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