- dof in a print varies with the print size and viewing distance. Smaller than 6x9 inch prints (from the whole frame) show more dof than assumed in the formula calculations. The formula assumes an 8x12 inch print viewed at roughly the diagonal length of the picture i.e. 12-15 inches with normal eyesight. Going back in time viewfinder screens were ground much coarser, were very good for judging dof but were relatively dark. Then along came the OM1 with new technology and much brighter screens. Since then autofocus and multi spot metering has been invented. To make it work there are tiny slits in the mirror which divert a lot of light via a sub mirror to the AF and auto metering modules. To get round the loss of light screen magnification is smaller than in "OM" days and they are ground finer to transmit more light, making them less suitable for judging dof. The D3 viewfinder is around 2 stops darker than an OM4 with a series 2 bright screen, primarily because a lot of light is diverted for metering and AF before it gets to the viewfinder. Out of interest what print sizes were you viewing and at what distance?
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.