[MF3D.FORUM:999] Re: Mounting tips?

["David Lee" <koganlee@xxxxxxxxxxxxx>]

----- Original Message -----
From: David W. Kesner <drdave@xxxxxxxxxx>
To: Medium Format 3D Photography <MF3D.Forum@xxxxxxxxxxxxx>
Sent: Monday, July 31, 2000 6:16 AM
Subject: [MF3D.FORUM:998] Re: Mounting tips?


> Paul Talbot writes:
>
> > However, shouldn't the
> > new Fn marks that you propose have different spacing than the
> > Fn marks for infinity?  When bringing something through the
> > window, it's usually a small amount of the overall depth, not
> > nearly a full 2+mm of OFD.
>
> I may be really confused here so is the maximum on film
> deviation the distance between the farthest homologous points
> when the window is at zero or is it when the closest object is
> at zero?

It seems to me that the point of even talking about deviation is in relation
to what looks best to the average viewer's eye. From that standpoint it
makes no difference where the near point is compared with the window or even
if the window is placed accurately. The deviation would be the same whether
the window was at the near point, the far point, or anywhere else. By the
way, because some people call it the "maximum on film deviation" does not
mean that it has to be that way. I wouldn't go much more than that myself,
but in practice I find that 50% more than that is no problem.

> If your closest object is at the window then you will have a
> "v" with the overlapping points at the apex of the "v" which
> is at the window. If your closest object comes through the
> window then you will have an "x" with the overlapping points
> at the cross-over which is at the window.
>
> Let's say you have an image with 4.0mm deviation at infinity
> when mounted with the closest object at the window ("v"). If
> you bring the close object through the window ("x") to a point
> where infinity is now at 2.0mm deviation that means that the
> near point will also be at 2.0mm deviation (from the window).
> Is this still 4.0mm total on film deviation or is it 2.0mm?

It would be 4.0mm by definition. (Far point separation minus near point
separation.)

If the window placement really affected the way the deviation was
experienced by the viewer, then anytime there was an excessive deviation one
would just have to mount it so that the excess was in fromt of the window.
Discounting the problem of incorrect window placement this obviously could
not be a solution to the problem, because the amount of deviation would not
have changed.

David Lee