Most likely that the DOF scales on lenses are almost without exception designed with a fairly large Circle Of Confusion value left over from film days. With digital sensors, you get more resolution per square millimeter than you did with film. While that is great for increasing overall resolution and image detail, an unavoidable side effect is that DOF is much narrower than when shooting with film, at least if you define "in focus" as pixel-sharp detail when viewing the file at 100%. A 2-stop difference would sound about right. If this is your concern, read this article and download the DOF calculator spreadsheet. If you fill in the sensor size and resolution fields correctly, it will accurately calculate DOF where DOF is defined as pixel-sharp focus when viewing the file at 100%.
The other possibility (if I'm not understanding your question correctly) is that the focus scale on your lens is not set correctly, and the infinity mark is misplaced by 2 stops on the DOF scale. If that is the case, the lens will need to have the focus scale ring adjusted so that the infinity mark corresponds to actual infinity focus.
[a href=\"index.php?act=findpost&pid=144272\"][{POST_SNAPBACK}][/a]
Jonathan/Eric,
If it is a Lens Focus Ring Scale "mis-alignment", I'm disappointed in Schneider. This is a brand new Digitar lens, supposedly designed to perfectly mate to a Phase type digital back! That's what we pay extra for, right?
If the person that purchases ones of these expensive lenses has to do his own personal calibration test for a lens that is two full stops off, then I think I should invoice Schneider for my time. I can see having to "tweak" a lens by say 1/4 stop, but two is very concerning to me.
Due to the historic excellence of Schneider lenses, I'm prone to discount the fact it's the lenses error - which is probably part of what I'm doing wrong. But IF I put the Phase P45+ back on my Hasselblad 503cw with the Hassie 100mm lens and run the same tests, I get the same error.
Thus, my logic at the moment is same back on different camera bodies and different lenses gives same 2 stop error must be a back issue. Couple that with the fact that images from the Loaner P45 have more saturation and color balanced indicates a faulty back.
Make sense?
Not really if one considers that we are dealing with products from engineering marvels and compenents that are prices in the Ozone!
But reality and perception frequently have little to do with each other.
Jack