[MF3D.FORUM:371] Re: 1/fl

["Bill Glickman" <bglick@xxxxxxxx>]

John B

       Are you saying if we use your formula, that we should vary the
deviation based on the fl lens used?  On my test shots using your formula, I
was planning to use 2.7 for all fl lenses... is this correct?  If not, what
is the relationship between deviation and the different fl lenses I plan to
use?

Thanks
Bill G



----- Original Message -----
From: <Tloc54452@xxxxxxx>
To: Medium Format 3D Photography <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Sunday, April 02, 2000 5:36 PM
Subject: [MF3D.FORUM:370] Re: 1/fl


> In a message dated 2000/03/29 18:54:49, tmd@xxxxxxxxxxx writes:
> >>Also, I find it's been so long (relative to the length of my
> >>memory) since I've done MAOFD, that it's a bit vague now.
> >>Can someone explain the 1 over focal length argument to
> >>me or cite me on the subject?  Sure would appreciate it.
> >
> >Heck, I cite you all the time, John.
> >
> >http://www.werple.net.au/~kiewavly/bases.html is a beautiful thing.
>
> Thanks for the reference, Tom.
>
> I didn't study it really closely, but I didn't see 1/fl right off in
there.
> However, Oleg came over Friday to take pictures of the hills behind
> my house and he uses a different cheat sheet for each focal length.
> Then it dawned on me that he's keeping the on-film deviation constant
> at something like 1.2 mm regardless of focal length.  And that's what
> generates the 1/fl rule.  That's the rule that old what's-'is-name
> used to use, I'll never forget his name.  Since I've not experimented
> with viewing from other than the center of perspective, I can't comment.
> However, it does seem logical in a way.
>
> On the other hand, if you are shooting for projection, you are planning
> on a longer distance from observer to screen so you should use a longer
> focal length and can use more on-screen deviation than if your viewing
> distance were for 50 mm or 35 mm lenses   On the other other hand, I
> think Oleg said he shoots for the hand viewer, and slide competition
> is incidental to his main aim (correct me if I'm wrong).  In this case,
> going with the 1.2 mm limitation sounds right, though I've not tested it.
> I know what's-'is-name would agree, and he does 3D for a living.
>
> So it looks like we have three rules going:
> 1) Constant maximum on-film deviation regardless of focal length
> (but dependent on format: 1.2 for 35 mm format, 2.7 for MF, etc)
> 2) base = near point/30 regardless of focal length
> 3) on film deviation = focal length/30
>
> #1 I attribute to what's-'is... Aha!  Good old Bob Mannle!
> #2 is the common rule from Ferwerda, for example
> #3 is Spicer's and my rule which can be back-derived from
>    Ferwerda and Waack, at least their advanced sections
>
> John B
>