I read a little on the concept of DOF and CoC this morning :
Concerning DOF :
(There is an interesting paragraph concerning the relationship between DOF and format)
and concerning CoC
Someone earlier in this thread wrote that Zeiss was using D/1730 as opposed to D/1500 as the CoC.
Here is what one can read about the size of the CoC in the wikipedia pages linked above :
Using the “Zeiss formula”, the circle of confusion is sometimes calculated as d/1730 where d is the diagonal measure of the original image (the camera format). For full-frame 35 mm format (24 mm × 36 mm, 43 mm diagonal) this comes out to be 0.025 mm. A more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm format, which corresponds to resolving 5 lines per millimeter on a print of 30 cm diagonal. Values of 0.030 mm and 0.033 mm are also common for full-frame 35 mm format. For practical purposes, d/1730, a final-image CoC of 0.2 mm, and d/1500 give very similar results.
But here is what I found about that Zeiss formula : it has nothing to do with the Zeiss Manufacture, but only with the fact that the tests conducted to compute that result were made using a Zeiss lens, as is explained there :
The Zeiss formula is apocryphal, in the sense that it has grown to be a well-known named concept by propagation through the internet, even though it has no official origin, little connection to Carl Zeiss Company, and no recognition or usage in the photographic industry outside the web community.