This is my understanding, and I hope I can explain it without sounding too dumb.
A 24mm lens is a 24mm lens is a 24mm lens. Even if you epoxy the sucker for a
hood ornament on a three-door Edsel dump truck, it's still a 24mm lens. It is
an inanimate object, always unaware, forever unable to alter any of its
physical characteristics. Therefore, it always and forever projects the same
image out its behind relative to the scene in front of it, meaning, assuming
the lens-to-film (or sensor) distance is correct, even the foot/meter distance
scale will be correct, and, obviously, the COC, DOF and FOV will be the same.
Just because you're capturing only half the image circle (a.k.a FOV) doesn't
make one iota of difference in the characteristics of the image the lens
projects. It doesn't know if it's been attached to an Olympus E-1 or, by use
of a bag bellows and a recessed lensboard, to a Sinar P2 8x10, or even hung as
an ornament on a Christmas tree.
Walt, awaiting correction and profoundly elucidating clarification of the
correction
--
"Anything more than 500 yards from
the car just isn't photogenic." --
Edward Weston
-------------- Original message ----------------------
From: R.Jackson <jackson.robert.r@xxxxxxxxxxx>
>
> Excuse me if I'm full of crap on this one, but I seem to recall that
> DOF is relative depending on factors having to do with the circle of
> confusion. I've always thought that's why it's harder to get selective
> focus with Super-8 than with 16mm and easier still with 35mm. That's
> one of the reasons people are so excited about Panavision coming out
> with a full-frame digital camera because now DOF with 35mm
> cinematography lenses will function properly. I'm sure some of our more
> technical brethren will be able to illuminate this all more precisely
> with trig equations and calculus functions that I won't be able to
> follow, but I thought I'd chime in with my art-boy synopsis. ;-)
>
> On Mar 27, 2005, at 10:10 AM, Walt Wayman wrote:
>
> > Perhaps someone would explain to me why the DOF would be any different
> > from what the scale on the lens indicates. It's still a 24mm lens,
> > and just because it's on a digital whatzis that captures only the
> > central portion of the projected image, making the FOV equivalent to a
> > 48mm lens on a real -- excuse me -- on a film camera, shouldn't change
> > the DOF. Should it? Would it? Does it?
> >
> > If I duct tape my 150/5.6 Schneider Symmar to the proper extension
> > tube combination and attach it to an OM body, the DOF in the
> > little-bitty bit I capture on 35mm film would be the same as the DOF
> > in that same central portion on a 4x5 in. piece of film.
> >
> > Please show me the error in my thinking and give two examples.
> >
> > Walt, using an analog analogy
>
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