[rollei_list] Re: new direct b&W slide film by Rollei

  • From: bigler@xxxxxxxx
  • To: rollei_list@xxxxxxxxxxxxx
  • Date: Tue, 3 Oct 2006 10:24:56 +0200 (CEST)

Yes this Slide Direkt Rollei film looks fascinating.
http://www.fotofenster.de/news/2006/09/rollei_retro_slide_50.html

I am a bit puzzled by the physics and chemistry involved beyond this.
Characteristic curves of this film can be found here :
http://www.fotohuisrovo.nl/documentatie/RolleiSD.pdf

I know that Kodak used to manufacture a direct copy film name Kodak
Direct Duplicating Microfilm 2468 

http://www.kodak.com/US/en/dpq/site/TKX/name/DuplicatingFilmsProduct
and also #5360/7360 
http://www.kodak.com/US/en/motion/products/curves/c5360.shtml

and 

KODAK AEROGRAPHIC Direct Duplicating Film 2422
http://www.kodak.com/eknec/documents/f8/0900688a802b09f8/ti0573.pdf

http://www.kodak.com/US/en/dpq/site/TKX/name/DuplicatingFilmsProduct

I have no idea whether these films still exist but a direct positive
slide is film is certainly not unheard of.

The informations I had read were that the film used the solarization
process, so the film was supposed to be pre-fogged and subsequent
exposures would place it in the negative slope of the extended H&D
curve. I had never found the explanation really satisfactory at least
as far from I had seen from solarization curves which appeared like
tiny bits of a negative slope after saturation. Something I would
never imagine to be useable in the real world, except by Ansel Admas
and his famous "black sun" image ;-)

The characteristic curve of the new Rollei direct slide film seems so
perfectly smooth and so linear (in log-log scale ;-) that it is really
puzzling.

Sure I would like to test it. 120 rolls are announced for April 2007
at a retail proce of 6.75 euros. Not cheap but definitely cheaper
(even if you include some drops or rodinal and some drops of fixing
bath) when compared to Scala film nd its dedicated professional
process.

Carlos Manuel mentions the extremely fine grain and high resolution of
this supposed-to-be orthochromatic film.

This is an excellent reason to re-visit our classics in silver halide
photography ; I have always taken for granted that ortho film
delivered a much better resolution than panchro film, simply by
reading the specs, but to date I realize that I do not have a simple
explanation why it is so. 

Why does red light sensitivity actually impairs the resolution of a
film ? I have noticed for example that the FTM curve of a color film
is not as good in the red layer as in the blue layer. Is it simply the
more complex structure of a panchro film vs. an ortho film than
degrades resolution ? or what else ?? I cannot imagine that it is only
a question of wavelength-related diffraction effect, since 320 lp/mm
are equivalent to a blur spot of about 3 microns, this is 4 times
bigger than the limit wavelength of "actually visible" red light at
about 750 nm.

BTW although the sensitiviy of the human eye to visible light is
suposed to be well-known at least since the 1931 CIE curve was
published, I have found an excellent article giving more details :

http://www.4colorvision.com/files/photopiceffic.htm


-- 
Emmanuel BIGLER         
<bigler@xxxxxxxx>
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