Quote Originally Posted by Ian C View Post
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.