Lars,
Can you see what is in and out of focus on a negative (or slide) without
magnification? If you can, then it would still be outside of the depth
of field on any print size, but if you cannot see that an object is
outside the depth of field on the film with the unaided eye, then on a
print that is the same size as the neg, you wouldn't see it either. If
you don't see that it is *not* in focus, then it is considered in focus
for that size of print. That is what depth of field is all about
(basically we should call it "close enough to in focus" because only
objects in the exact plane of focus are fully sharp) Maybe not up to
4x5 either. Maybe at 8x10, though you can start to see that the object
you are looking at is fuzzy compared to objects at the exact plain of
focus. This all is contingent on viewing distance as well. (the
fundamental reason behind all this is that photographic materials are
capable of containing more detail than the human eye is capable of
seeing unaided. This is just the interaction that arises as you magnify
the photographic materials enough to start to see the detail that was
"invisible" before).
Yes, once you get large enough, everything is pretty blurry and fades
into the grain, and that is where you reach the absolute limit of
sharpness which defines the "true" DOF, but this limit is much, much
narrower than what is calculated by most DOF calculators because of
their assumptions on acceptable size of CoC based on a print size
smaller than one where everything becomes somewhat soft.
This threshold limit also changes with film type and technology. This
limit may have been the original CoC size that Leitz used to determine
as the limits for DOF, but it has changed significantly due to film
technology. Merklinger treats this whole development in one of his essays.
Mike
Lars Michael wrote:
>
> So, are you saying that you can make a subject appear in
> focus on print if it is not in focus on the negative,
> simply by changing the print size?
>
> What is in focus on the neg is in focus, and what's not
> that's not. Print away all you want, there's no way
> around it. Of course for large enlargements you obviously
> also have to enlarge the grain, so you loose tonality,
> but that has nothing to do with the DOF during exposure.
>
> I think you are talking about film grain. DOF has nothing
> to do with the recording medium. DOF is present even without
> a neg or print.
>
> Lars
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