Originally posted by Rytis DOF calculator doesnt help, before , using 35mm FX cameras never came across with a problem like this,even if i use scale on the lense, im avare that dof in 35mm slightly larger than on 44x33 mm sensor,but still,how to explain f16 , focus set on 4 metres and i get only foreground in focus
DOF is now equal to COC. DOF it is not calculated in a useful way by so called "DOF calculators". DOF is not absolute - many people like to think it is, but it isn't. It can be affected by tiny vagaries of manufacture, optical alignment, optical design of the lens.
In a nutshell: DOF is about the region of acceptable sharpness*. The absolute point of focus is always going to be sharper than elements in front or behind it** - all DOF scales or "DOF calculators" do is give you a loose idea of how in focus, or out of focus objects that are in front of or behind the point of focus will be.
Remember when you are looking at your images from the 645Z at 100% or 400% on screen, you will see things that will probably not even be visible on a 36"X24" inch print. Remember the optimal viewing distance of an image is based on the diagonal dimensions of the image - of course this is a rule of the thumb, some people like to look at images at closer distances than this, some at further distances. But it pays to keep this in mind when producing images for display.
*
sharpness is a relative and subjective thing, and that is the premise on which DOF claculators function.
**at least until diffraction kicks in, which limits the maximum amount of sharpness on the plane of focus a scene. It is possible to stop down to the point where nothing will be critically sharp. But on a 8X10 print, who will notice?