P3D Re: Realist vignetting

[Eric Goldstein <egoldste@xxxxxx>]

Tony Alderson writes:

> But with ASA 10 film,
> nobody used f16 anyway.

Tony-

Not for snapshots but f/16 and f/22 were used during that period and are
useful today. One example both for then and for now would be in shooting
time exposure where we wish the shutter to remain open for a significant
period for purposes of selective motion blur (and don't want to find
matching N/D for both lenses!). The Realist 3.5s vignetting at f/16 as
you point out is indeed a design flaw and IMO not an inconsequential
one. With the individual variation you find in cameras of the period,
some Realists and Reveres are worse than others so one might test before
buying...

> Even today, f16 on a Realist doesn't get you much
> but exposure convenience.  f8 has all the depth of field you can handle for
> projectable slides, so you won't see a sharpness difference at f16 vs. f11.

I suspect that the vast majority of shooters and slides never see the
light of a projector so this might not be essential to most. Also, f/11
I think is still a useful aperture for projection and I have comfortably
viewed projected slides with 6 to 7ish ft -> inf worth of DOF and have
lived to tell about it! 8-)

If this much deviation is projectable and/or viewable, then f/16 takes
on another important role by allowing us not increased DOF but reduced
CsOC at the same points of focus, say to f/1400 from f/1000 (the
standard used by realist). If sharpness and clarity are sought, then
setting the focus for 14 feet and shooting at f/16 could serve this
useful purpose, and I feel this difference is quite visible in the hand
viewer and certainly obvious with higher orders of enlargement.

One of the well-known downsides of shooting these smaller apertures is
that lens performance (resolution) typically begins to fall off with
these lenses after about f/8-11 due to diffraction and so there is a
tradeoff here...


Eric G.


------------------------------