|
I noticed that the Maco Rollei R3 pdf brochure (& the Freestyle Photographic Supplies webpage based on it) describes the film's spectral sensitivity as "super-apochromatic". This of course should be "super-panchromatic", since a _film_ doesn't focus different wavelenghts at different points from the objective, not to mention the other requirements of the definition "apo"! (Thomas Back's discussion of this is the best I've come across: http://voltaire.csun.edu/tmb/definition.html ). I'm very surprised that Rollei, of all people, would allow this serious error get into their promotional material. On the plus side - this R3 film looks like it has one unexpected benefit for medium format astrophotographers: film flatness! There is quite a lot written in the pdf brochure about how stiff it is compared to "the usual triacetate films" in medium format: "The polyester film support is much stronger mechanically than normal triacetate bases. As a result, the material exhibits a certain amount of stiffness. This may cause medium-format roll film to snap open as the tape holding the roll is removed." This tendency of the film to straighten itself out and hold its stiffness should in principle be good for maintaining film flatness during long exposures, as well as reducing or eliminating the 'frame kinked from sitting on the rollers for a while' problem which afflicts cameras with a double-back film path (like Mamiya 645 & 67, Hasselblads, Bronicas, Kiev 88s, Pentax 645s, etc...) But the reciprocity specs look awful, so hypering would have to work well, for this film to be any good for deep sky. Ray "who has found film non-flatness to be the the gremlin in medium format astrophotos, more often than any other issue" Butler gbuckles@widefieldastrophotography.com wrote: Don, You may want to check this film out: Maco Rollei R3. It's a German B&W film that Freestyle Photographic Supplies carries in LA. It's available in 35mm, 120 and 4x5. The range is 380~710/730nm. Could be worthwhile. Here is Freestyle's product description. There is a link at the bottom for the .pdf tech brochure: http://www.freestylephoto.biz/sc_prod.php?cat_id=403&pid=1000000747 Freestyle also lists a Maco T64 in the OTHER film section as a "tech pan replacement". Couldn't find out much about it though. I think the Rollei R3 is the one to look at. Garth -- Dr. Ray Butler Lecturer, Physics Department & Computational Astrophysics Laboratory, National University of Ireland - Galway, University Road, Galway, Ireland. Web: www.nuigalway.ie/physics/ Email: ray.butler-AT-nuigalway.ie Tel: +353-91-493788 FAX: +353-91-494584 |
_______________________________________________ Astro-Photo mailing list Astro-Photo@seds.org http://seds.org/mailman/listinfo/astro-photo