Re: mystery filters!

[Michel Wurtz - LTE <mw@xxxxxxxxxxxxxxxxxxx>]

Jaap Los wrote:
> 
> Hi all,
> Like to have your opinion about following mystery. I have done some
> testing of HIE with all sorts of odd filters, which I placed between the
> film rails (btfr). I did 2 tests.
> 
> Test 1
> I made a filter of unexposed fresh Ektachrome Elite 1 35 mm slide film
[...snip...]
> layer of the film. So I decided to develop the film according to my
> standard procedure in XTOL 1+1 etc. (just ordinary black/white dev. on a
> colour film!). After fixation and drying I had my 2nd filter ready. This
[...snip...]
> My prelimary conclusion is, that the 2nd made filter blocks much more IR
> than the 1st made flter. I can't explain why. Next week I will run
> another test whereby I will bracket up till at least +10 with the 2nd
> filter. Is it possible to obtain sharp pictures by using these types of
> filters? Is there anybody on the list having experiences with
> "film-filters"?

I have a (theoric) explanation, maybe someone will confirm :

1st filter is made with color dyes (bleach bath remove all silver),
so the light is filtered mainly in the visible light.

2nd film is black because of the silver (no color can be generated
by a B&W developer) => it's a "metal" filter, which block IR at the
same ratio than visible Light.

For the blur, I've noticed that the optical quality of an ektachrome
slide is far from perfect.  I suspect ther is too much layers (3)
in the film and that the support is not designed to be a filter.

I prefer the solution of making a sanwich with a #29 and a #58 (green)
filter.  That gives something close to a 89B...

- -- 
Michel Wurtz    ENGEES - Laboratoire Territoires & Environnement
                1, quai Koch - BP 1039, F-67070 STRASBOURG cedex
                Tel: +33 03.88.25.34.62  Fax: +33 03.88.37.04.97
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