----- Original Message ----- From: "Laurence Cuffe" <cuffe@xxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx> Sent: Friday, April 03, 2009 3:12 PMSubject: [rollei_list] Re: RPA, Efke 25, fixer with hardener?
On Friday, April 03, 2009, at 02:52PM, "Richard Knoppow" <dickburk@xxxxxxxxxxxxx> wrote:----- Original Message ----- From: "Robert Lilley" <54moggie@xxxxxxxxxxxxxx>To: <rollei_list@xxxxxxxxxxxxx> Sent: Thursday, April 02, 2009 4:37 PM Subject: [rollei_list] Re: RPA, Efke 25, fixer with hardener?I imagine you could rig a sheet film holder to take a glass plate - just dremel out the additional depth and don't usethe other side. Rob On Apr 2, 2009, at 6:44 PM, Mark Rabiner wrote:Plate holders were available on the used market until not too long ago, perhaps a search would find some. Plateholders have a spring inside which presses the plate againstthe front of the holder. Kodak made plates coated with T-Max emulsion until about ten years ago. These were made mostly for scientific photography but electronic imaging has take over there. Astro photography has relyed on electronic sensors for decades now. The glass plates mentioned earlier sound like someone's home made jobs and might be based on very old technology. -- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxxRichardThe plates I mentioned seemed to be an Agfa product, one which it appears Dr Biggler has had some experience of from what I read on a french photo groups web site, A cursory google reveals at least two manufactures of glass photographic plates for holography still in buisness. Details are available on the following web siteshttp://www.holokits.com/holographic_film_plates.htm#hologram_film_plates and http://www.townetech.com/holoplat.htm,Plates on the second site appear to be spin coated, which is probably an appropriate modern method of achieving an even coating. Holographic emulsions tend to have a rather uniform distribution of photosensitive crystals, and as such would tend to be inherently high contrast materials. Because of the high resolution necessary for good holographic results, they will also be fine grained and thus slow. Incidentally spin coating was the technique used by Mrs Thatcher (nee Roberts) in her research into Langmuir Bloddget films when she was a scientist before she went into politics. (H.H.G.Jellinek and M.H.Roberts, J. Sci. Food Agric., 2 (1951) 391.)All the best Larry Cuffe--- Rollei List
I think all of the principle photographic material makers made glass plates for scientific photography until fairly recently. They were used for all sorts of things requiring very good dimentional stability such as astro photography, elecron microscope photoraphy and similar applications. While adaptors were available to make glass plate holders work for film I don't think the opposite is possible. The sheaths were metal sheets with edge clamps for the film just like those in sheet film holders. The thickness of the back plate was such as to locate the film in the correct plane. Some years ago I saw a lot of plate holders show up at local camera swap meets but have not seen any in the last couple of years. Sheaths were never plentiful. Glass plates were gradually supplanted by sheet film over the decades from the 1920's to 1940's but made a resurgence, especially for press work, during WW-2 when both cellulose nitrate and acetate were in short supply due to their use for explosives and other military uses.
-- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org
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