Re: Filter questions

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

On 24 Feb 01 at 20:35, Keith Zimmerman wrote:

> I'm planning for the up-coming release of this year's Konica by increasing
> my tool inventory of filters.  I have a couple of quick questions.
> 
> 1.  Can someone discuss the optical pros and cons of the various materials;
> polyester, gelatin, resin, and glass.
> 
> 2.  Is there a site anywhere that has this type of information?

You might want to check a chapter on my homepage to get some idea 
about the availability of colors & materials:

http://www.a1.nl/phomepag/markerink/irfilter.htm
 
> 3.  Which material works best?  Or are there instances when one material is
> better suited than another?

Definately....for example, the most foolproof method of mounting an
IR filter, BTFR (between the film rails), doesn't leave you much
choice....the only material thin enough is thin foil, either
gelatine or polyester, and of which gelatine is probably too
fragile, expecially when darkloading (in all 3 aspects that makes
gelatine fragile: fingerprints/humidity/scratches). 
OTOH, polyester is limited to #87C as the darkest color, darker 
thin foil only exists in gelatine (while Kodak doesn't make the 
darker ones anymore (or at least they didn't until recently), 
alternative products do exist, mail me if you are insterested).

> 4.  Which filters would be candidates for inclusion in my new IR toolbox?  I
> currently own a 25.

For all IR/deep-red films apart from Kodak HIE, I would recommend a 
#89B....HIE easily takes a #87C, but focusing & composition isn't 
easy with opaque filters, which leads you to the BTFR solution quite 
quickly....;))

Darker than #87C for HIE results in an awful slow film....I recently
tried a #87A-equivalent with 1/15s @f2.8 (effective ASA is 0.5
ASA....:)), on a bright (alpine) sunny day, but apart from some
solar disc images, all my frames were clear....:))....gotta repeat
that in summer with abundant foliage, but I am afraid it's tripod
all the way anyway....

Same argument of slow speed is for Konica & #87....you do get the 
strongest IR effect possible on that film, but the price is speed....

--                 
Bye,

Willem-Jan Markerink

      The desire to understand 
is sometimes far less intelligent than
     the inability to understand

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