[pure-silver] Re: (slightly OT) Film flatness in a 4*5 holder

  • From: <C.Breukel@xxxxxxx>
  • To: <pure-silver@xxxxxxxxxxxxx>
  • Date: Wed, 4 Apr 2007 13:57:49 +0200

Hi Rob,

Thanks for your input: I guess the main object of the test is its
infrared chracteristics, ie how well it will record the infrared
spectrum (the film is said to be senstised upto 820 nm). So sharpnes
isn't the main issue yet.

I'll be shooting mainly landscape with some houses. Tonight I'll check
if sliding a piece of normal sheet film underneath the thin film is a
solution (i.e. if the film will be lying flat than, theoretically the
sandwich is too thick, but I assume for the landcape stuff I indend to
shoot at f16-f32 that should not matter).

On the antihalation layer: at one time MACo markerted AURA film, which
was basically a MACO 820c film (aka EFKE PL100 plus IR senstive dyes)
without an anti halo layer. I was asked to test it out, but no matter
how hard I tried I could never obtain the halo effects chracteristic of
Kodak HIE, there was a very small difference between the AURA and the IR
820c film.


Best,

Cor

> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-
> bounce@xxxxxxxxxxxxx] On Behalf Of Rob C
> Sent: woensdag 4 april 2007 13:28
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: (sligthly OT) Film flatness in a 4*5 holder
> 
> I don't think anyone could answer your question with 100% certainty
for
> several reasons.
> 
> For starters, if the film is loose in the holder, then it may be
tilted
> one way or another and also the center may or may not be in the
correct
> plane.
> And it depends on what you have focussed on in the subject. i.e. was
the
> focus point in the center of the frame.
> Also, some IR films have no antihalation layer and different IR films
will
> react to halation in different amounts. This may cause some films to
> appear less sharp than others.
> And was your subject planar and fill the frame completely so that you
> would expect the same sharpness from edge to edge.
> And was your lense at optimum aperture to obtain sharpness edge to
edge.
> 
> Depth of focus increases the closer your subject is to the camera so
if
> you want to remove depth of focus as a significant factor from your
> testing, do some macro shots. But of course you then have to worry
about
> depth of field which is much reduced. But then if your subject is
planar
> then depth of field won't be an issue either.
> 
> So your test results would depend on many factors and I guess it also
> depends on what you are supposed to be testing. i.e. subjective or
> objective tests.
> 
> Rob C
> 
>
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  • » [pure-silver] Re: (slightly OT) Film flatness in a 4*5 holder