Re: IR pol's & 70mm (was: Newton Rings)

[Willem-Jan Markerink <w.j.markerink@xxxxx>]

On 19 Jul 96 at 15:36, Chris Eastwood wrote:

> >FotoMagazin (German): two nekkid kids playing along the shoreline 
> >(sp?), resulting in two sparkling bright bodies in front of a pitch 
> >black sea, with nice white gulf breakers. 24mm wide angle 
> >perspective. Very nice. 
> 
> Yep ... when you gettin that IR polarised bit goin?  I stil wanna get rid of
> reflections off the water in my IR's (and I know you do too) ... 

Well, that project is sorta stuck in the middle.
First, for all pondering what on earth an IR pol should do: according 
to many sources (including my highly technical German books, and a 
tech rep at B+W), polarizers don't polarize much beyond 750-800nm.
In real life, I hear mixed opinions about this, so I would welcome 
any practial comment from you. Keep in mind that the lack of effect 
mostly shows with a dark IR mounted, otherwise you see also the still 
existing pol effect of visible light in the picture.

(PS Ken Sinclair: you said one of your friends was fiddling around
with this too....could you or your friend elaborate on that? (could
you introduce him to this list?)

Anyway: 
Real IR dedicated polarizers are insanely expensive, about $600 for a 
10x10cm piece of foil, not even glass mounted. They also incorporate 
a rather dark red filter, so their practial use is limited (a pol is 
no good if you can't check the effect with your bare eye). The next best 
solution was a custom order thing, but the final product was not 
suitable for image purposes, it was far from optically flat. For 
light purposes, such as with IR lasers, this would be fine, but not 
for photography. The second best solution I now also have a sample 
from, but I have not managed to do extensive testing.
I must note that I currently test these filters with one of my night scopes, 
added with a dark IR filter. That way I want to exclude general density 
differences that would show on film, due to different IR colors (the 
best pol has an filter build in). 
Major confusing stuff, not to mention the extinction and cross 
polarizing data tables my supplier sent me.
 

> >I only once took HIE to the beach, but it was soo hot I think I 
> 
> Winter?

Mmm....that might get me sued for child abuse....don't think I can 
get kids playing in the surf at those temperatures....;-))
Mmm....maybe I should add one of those thermo electric coolers on the 
back of the camera....mmm....;-))

 
> >Must remember to do this again with my Horizon; beaches are a perfect 
> >subject for panoramas.
> 
> Anything is perfect fer Panp's but that is another list mate ... you weren't
> a bee in yer past life (cross polinating and all ;-)

Who knows....my 8mm Sigma surely launches me into the world of 
fish....;-))
 
> 
> Is that Horizon of yers 35mm or 70mm??  I didn't think that HIE was
> available in 120 roll...

Nope. It is said to have something to do with IR leaks through the paper 
backing of 120. That's why 70mm in cartridges does work. Both HIE and 
IE are available in that size, Aerographic IR and Aerochrome IR 
respectively. I can only hope they also convert Aerochrome IR to E-6!

Regrettably there are no swing lens pan cameras for 70mm, only a
film rotating pan camera from Seitz, for about $6000....:-(( The
bright side is that this one also accepts 220 roll film, otherwise
it would become an insanely dedicated investment....

I once even haunted some Noblex engineers about this, but the 70mm 
sprocket mechanism is much to complex to add to a camera. Spools are 
much easier.
*A* solution, one that I would like to try sometime, is respooling 
70mm down to 120 size, and load the camera/back in complete darkness. 
If you load several backs, this could get you going for some time.
Dark loading inside a bag seems horror (it already is in my Horizon), 
so this is certainly a dark room job.
Anyone done this?



--
Bye,

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The difference 
between men and boys
is the price of their toys

<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]