Re: Pressure Plate Reflectance

[Steve Homer <shomer@xxxxxxxxxx>]

Andy --

I've used both 120 backing paper and black vinyl tape over the pressure
plate shooting Kodak IR Aerographic, and I did not notice a change in
overall density. I suspect there was a change -- your concern makes perfect
sense in theory -- but it was smaller than I expected (or noticed).

The number of stops you lose would depend on how efficiently the pressure
place reflects IR. I assume that my RB pressure plate didn't reflect IR very
efficiently in the first place, which is why I didn't notice a change in
density. (I was trying to hide the pattern of holes on the plate, not reduce
halation.) Very possibly, other pressure plates are much more IR reflective,
so the answer to your question could be camera-dependent.
____________________________________________________
Steve Homer    shomer@xxxxxxxxxx   Santa Cruz, CA  USA
 
> Date: Sat, 28 Apr 2001 17:16:03 +0100
> From: Andy Finney <andy@xxxxxxxxxxxxxxxx>
> Subject: Pressure Plate Reflectance
> 
> If I tape non-ir-reflective tape over the pressure plate in the
> camera I presume that will reduce the light bouncing back through the
> film and therefore reduce the exposure as well as reducing the
> halation? Is that correct.
> 
> If so, assuming a completely ir-black plate, how many stops would I lose?

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