Re: Novel Mounting Method

[s.spicer@xxxxxxxxx]

John Bercovitz wrote:

> In mounting to infinity, you put infinity homologues the correct distance
> apart for the format, usually somewhere around 63.5 mm.  Now if you put a
> notch in each film gate directly behind each lens as Steve suggested, you
> will create an artificial pair of infinity homologues.  This pair can be used
> regardless of whether or not actual or convenient infinity homologues exist
> in the pair.

Michael Kersenbrock wrote:

>For this method, wouldn't something like a corner or edge of the image work
>better than a notch?

That sounds like an excellent suggestion. It would be worth making sure
that the distance between the frame edges that you decide to use equals the
lens separation. That might sound silly, but on the stereo cameras I have
the film gate frame isn't made that precisely. Nevertheless - it could be
made to work. A practial point is that it would be hard to see the gauge
markings when they fell onto the black film 'tween images.



>Seems like a notch along the bottom or top (to get
>horizontal alignment) would sometimes be hidden by the portion of the mount
>being used to hold it there.

I agree - I haven't tried this in pratice - it could make the method
unworkable. But for my own mounting jig I can see image outside the mask
while mounting - although dimly lit.


>What is the other "near" notch mentioned in the suggested algorithm for, and
>when would it be used rather than the "far" notch?

I don't know what it could be used for. Maybe I'll think of a situation an
a minute. ;-)  ;-)  I sort of realised after I posted that you really only
need the infinity mark to mount-to-infinity. So I agree with that point
too.

John Bercovitz has already emphasised that this is a "mount-to-infinity"
solution. The ironic part is that my own mounting method is to
"mount-to-the-window". And here I am posting about mount-to-infinty methods
;-)  ;-) So I probably won't be pursuing the use of the scheme I oultined!
But it is interesting to know about these things.


> > Seems that if fixed spacing would work, then Kodalux machine mounting would
> > work perfectly because I assume the chips themselves are machine aligned to
> > constant distances apart.
>

Well I can't comment on Kodalux. Unfortunately, out in the nether-regions
of this world we can't get commercial mounting services. But I would
imagine that the required tolerances in the mounting machine would be hard
to acheive and maintain.

The scheme oulined (and Kodalux) will fail for close-up work (for subjects
closer than 7 feet), because the subject will fall in front of the window.
Two ways to tackle that are: use a close-up mount and increase the distance
between infinity points when mounting (eg: have a gauge that sets infinity
points further apart for close-up mounts). Or use a different type of
close-up mount with the apertures spaced closer together and keep infinity
at 63.4mm apart.  Oh dear, I've digressed onto stuff that people already
know....

Or you can do what I do, and mount-to-the-window  ;-) ;-)

I still haven't thought of a use for the near-point marks you asked me
about. How embarrassing.


Steve Spicer
Melbourne, Australia



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