That's true of the negatives, Walt, but don't forget that a half frame
negative is enlarged twice as much as a full frame negar=tive ti get an
8x10. That extra enlargement "magnifies" the out-of-fcous areas on the
final print.
Thus the convention that DOF is related to format, specificaaly the size of
the circle of confusion is related to the diagonal of the format. Smaller
CoC gives smaller DoF, other things being equal.
Don't imagine that I am a stickler for the conventional view of DoF - as it
happens, I am not at all - but I do believe that the usable DoF from a given
lens will be different if a smaaler portion of the frame ends up on a print
of a given size.
--
Piers
-----Original Message-----
From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
Of Walt Wayman
Sent: 27 March 2005 21:25
To: olympus@xxxxxxxxxx
Subject: [OM] Re: Figuring out depth of field with 4/3 adaptor
Consider that using a lens intended for the 35mm format on a camera with a
half-size sensor really just amounts to in-camera cropping. The
perspective, depth of field, and everything else will be the same as if you
shot the scene on 35mm film and then cropped out the digital-size portion.
The receptor of the image has, or should have, unless it's defective, no
effect on the image itself. If I look out the kitchen window and see an
elephant in the front yard and I yell to my wife, "Come here and look at
this ***ing elephant in the front yard!" I would be more than surprised if
she came, looked out the window and said, "Elephant? That's a rhinoceros,
you moron!" Same thing here. Whether it's a whiz-bang digital sensor or a
primitive piece of Plus-X, the picture projected onto it is the same in
every respect. It's just that with a smaller format receptor, you don't get
the whole picture, and if it's an elephant, it's just going to be part of
the elephant.
Walt
--
"Anything more than 500 yards from
the car just isn't photogenic." --
Edward Weston
-------------- Original message ----------------------
From: "Michael R. Collins" <michael789@xxxxxxxxxxxx>
> >...A 24mm lens ... 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.
>
> Walt, this is where you lose me. No question the *projected* image at
> the sensor, whether it's 35mm film or 110 film or 8x10 film or small
> or large digital sensor, will have the same "sharpness" in that plane
> regardless of the sensor type or size. However, I have always
> understood DoF to be dependent not only on the lens but also the
> format - 35mm, MF, LF... (and also on assumptions made about viewing
> distance and quality of eyesight, but factor those out for now). For
> any given format, you use a factor (e.g., typically 5x for 35mm, less
> for MF and even less for LF) to account for a *viewed* image as
> opposed to the image projected on the sensor.
>
> The answer to the "digital DoF" question, then, would depend on the
> factor used, and is the same as for 35mm only if the factor is the
> same, which I doubt. I'm off to search the literature; no idea whether
> I'll find anything.
>
> There's a further issue of CoC vs. pixel size, which can be left for
> the next discussion :-) .
>
> Michael
> --
> Michael R. Collins ... Michael.Collins@xxxxxxxxxxxxxxx Toronto,
> Ontario, Canada
>
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|