FROM: zem_zeta@usa.net (christoph manz) SUBJECT: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Wed, 6 Sep 2000 16:39:02 +0100 NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm Tony Spadaro wrote: > I still wonder about my new Kindermann tops as they are not black but > grey - however it is an acedemic question since I will never use IR > film again. Just too much hassle for me. i guess the color of the top won't really matter as long as it is made of suitable material. as others said, IR leaking doesn't seem to be a problem with most plastic tanks any more - or at least i had never any problems myself - anyway, there's one easy way to make sure that there's no fogging: ** process in a room with fluorescent lights ** of course you still have to load the film in complete darkness but once the tank has been closed it's safe to switch on the light as fluorescent tubes emit almost no IR. frankly, every room with dimm light should do, just avoid direct sunlight... and even there Josh said it didn't fog in a test ++ christoph ++ ______________________________________________________________________ ++ for direct responses use ++ FROM: "B.B. Bean" SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Wed, 06 Sep 2000 11:45:29 -0500 (CDT) ORGANIZATION: Altopia Corp. - Usenet Access - http://www.altopia.com NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm On Wed, 6 Sep 2000 16:39:02 +0100, christoph manz wrote: >as others said, IR leaking doesn't seem to be a problem with most >plastic tanks any more - or at least i had never any problems myself - >anyway, there's one easy way to make sure that there's no fogging: > > ** process in a room with fluorescent lights ** > >of course you still have to load the film in complete darkness but once >the tank has been closed it's safe to switch on the light as fluorescent >tubes emit almost no IR. YIKES! In my experience, flourescents emit IR for several seconds after turning them off. I have several rolls of striped film that taught me this lesson the hard way. BB -- B.B. Bean bbbean@beancotton.com Peach Orchard, MO www.cris.com/~Bbbean/gallery.html FROM: zem_zeta@usa.net (christoph manz) SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 7 Sep 2000 00:20:25 +0100 NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm B.B. Bean wrote: > On Wed, 6 Sep 2000 16:39:02 +0100, christoph manz wrote: > > >as others said, IR leaking doesn't seem to be a problem with most > >plastic tanks any more - or at least i had never any problems myself - > >anyway, there's one easy way to make sure that there's no fogging: > > > > ** process in a room with fluorescent lights ** > > > >of course you still have to load the film in complete darkness but once > >the tank has been closed it's safe to switch on the light as fluorescent > >tubes emit almost no IR. > > YIKES! In my experience, flourescents emit IR for several seconds after > turning them off. I have several rolls of striped film that taught me > this lesson the hard way. hmm... i'm very surprised by this and i don't have any idea how something like this would be possible to happen... frankly i'm pretty sure that this must be an misunderstanding but i'm always eager to learn something new... are you sure you're not mistaking the IR radiation with fluorescent afterglow? how exactly did you process your damaged film? and have you any theoretical data to explain your experience? i'm not trying to be a smartass here, i'm just curious how fluorescent lights could emit IR _after_ they have switched off if there's hardly any IR radiation when they're on. anybody else has thoughts on this topic? ++ christoph ++ [posted and mailed] ______________________________________________________________________ ++ for direct responses use ++ FROM: nospam@verio.net (PhysicsMan) SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 07 Sep 2000 01:13:59 GMT ORGANIZATION: Verio NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm On Thu, 7 Sep 2000 00:20:25 +0100, zem_zeta@usa.net (christoph manz) wrote: >>...snip... >> YIKES! In my experience, flourescents emit IR for several seconds after >> turning them off. I have several rolls of striped film that taught me >> this lesson the hard way. >hmm... i'm very surprised by this and i don't have any idea how >something like this would be possible to happen... > >frankly i'm pretty sure that this must be an misunderstanding but i'm >always eager to learn something new... are you sure you're not mistaking >the IR radiation with fluorescent afterglow? how exactly did you process >your damaged film? and have you any theoretical data to explain your >experience? > >i'm not trying to be a smartass here, i'm just curious how fluorescent >lights could emit IR _after_ they have switched off if there's hardly >any IR radiation when they're on. > >anybody else has thoughts on this topic? First, who said there's hardly any IR radiation emitted when they are on? Second, lets get some terminology down. By definition and common usage in physical chemistry / spectroscopy, within very wide limits, for phosphors, fluorescence is fast and phosphoresence is slow. I don't know what exactly you mean by fluorescent "afterglow". About the only place the term "afterglow" is used scientifically is in the gas phase, where the term phosphoresence is not commonly used. If that is what you mean, you are correct that the Hg/Ar/etc/etc gas mix in commercial fluorescent bulbs will not have any appreciable afterglow because the strongly allowed 2537 A radiative transition of Hg comes from (if I remember correctly) one of the lowest lying electronic states in the mixture and will drain all the electronic excitation in nsec after the discharge is turned off. Third, although I'm not at all familiar with exactly what phosphors are used in commercial fluorescent lights, in general, organic phosphors usually have two types of electronic transitions possible, fast "allowed" transitions (usually singlet -> singlet) and much slower "forbidden" transitions (usually between triplet and singlet states). The 2537 Angstrom photons from the Hg in the gas pumps the phosphor to quite high lying electronic states. Usually, these states radiatively decay very quickly (ie, in nanoseconds) to the lowest lying excited electronic state which is often a triplet. Because triplet -> singlet transitions are very slow, and because the ground state is usually a singlet, then population builds up in this low lying triplet state and leaks out as long wavelength radiation (ie, near IR) very slowly compared to the prompt radiation from the upper cascades. This radiative decay can have time scales from milliseconds to minutes and explains (in some cases) IR coming out of a phosphor long after you turn the fluorescent light off. Now, if someone can tell me if the phosphors used in commercial fluorecent lights are organic or not, we may have solved the mystery. If the phosphors used are inorganic, the same general steps can take place, but depending on the exact material, there is much more variability in which states are the lowest, which transitions are slow and which are fast, etc, etc. Hope this helps. If anyone can add their $0.02 with more details, I'll be interested. Jim FROM: "B.B. Bean" SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 07 Sep 2000 09:32:38 -0500 (CDT) ORGANIZATION: Altopia Corp. - Usenet Access - http://www.altopia.com NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm On Thu, 7 Sep 2000 00:20:25 +0100, christoph manz wrote: >frankly i'm pretty sure that this must be an misunderstanding but i'm >always eager to learn something new... are you sure you're not mistaking >the IR radiation with fluorescent afterglow? how exactly did you process >your damaged film? and have you any theoretical data to explain your >experience? Unloaded HIE from camera in light tight bathroom immediately after turning off flourescent lights. All other handling done in changing bag. Non-IR film not affected by same handling, HIE film handled entirely in changing bag not affected. HIE film handled in same room several minutes after turning off lights not affected. Hence - the just-turned-off flourescents emitted enough light (presumably IR) to cause problems on HIE, but not on Tri-X. I've built a darkroom now, so the problem is no longer relevant to me. BB -- B.B. Bean bbbean@beancotton.com Peach Orchard, MO www.cris.com/~Bbbean/gallery.html FROM: David Littlewood SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 7 Sep 2000 20:11:39 +0100 NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm In article <39b6e5f1.457173240@news.verio.net>, PhysicsMan writes [snip most of interesting explanation] > >Because triplet -> singlet transitions are very slow, and because the >ground state is usually a singlet, then population builds up in this >low lying triplet state and leaks out as long wavelength radiation >(ie, near IR) very slowly compared to the prompt radiation from the >upper cascades. This radiative decay can have time scales from >milliseconds to minutes and explains (in some cases) IR coming out of >a phosphor long after you turn the fluorescent light off. > From what you say (which sounds as if you know quite a bit about this field) the low-lying triplet state presumably exists at an equilibrium level while the light is on, and the IR decay is thus continuous throughout; it then decays (exponentially?) over a period after switching off - but the logic then suggests that it must have been emitting the maximum IR all the time while on. It is easy to imagine how one could find this out the hard way (by exposing film immediately after turning off the light) without realising it (the IR component) was there all the time. Sorry, I cannot add any facts to your informative post. -- David Littlewood London Energy Consultant and Photographer FROM: David Littlewood SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 7 Sep 2000 20:16:48 +0100 NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm In article <8p6tps$57s$1@nnrp1.deja.com>, Tony Spadaro writes > Try turning off a flourescent bulb that is the only illumination for >an otherwise dark room and you will see the bulb glowing - or I should >say Some people will be able to see the bulb glowing - much depends on >the speed at which the individual's eye adapts. I'm not referring to a >retinal afterimage. This actually does happen. Some flourescents pulse >for a few minutes. > This is why flourescents are not used in Darkrooms. I have no idea >what spectrum this "afterglow" is in - other than visible. >-- Tony, you should know by now that making an assertion like "fluorescents are not used in darkrooms" on an ng is bound to prompt some awkward type to say "oh yes they are". My DR is illuminated by 2 fluorescent tubes, has been for the whole of the 12 years or so I have had it (I mean except when not illuminated, as it were). I have had no detectable problems with them, though (since I noticed the afterglow quite early on) I do allow at least 10-15 sec for the radiation to decay before opening film canisters. You are right, not what I would do if I was starting again, but can be lived with once you know. -- David Littlewood London Energy Consultant and Photographer FROM: w.j.markerink@a1.nl (Willem-Jan Markerink) SUBJECT: Re: IR opaque tank [was: Which tank for 35mm Hewes reels?] DATE: Thu, 07 Sep 00 23:20:44 GMT ORGANIZATION: A1 de Internet Provider uit Twente B.V. NEWSGROUPS: rec.photo.darkroom,rec.photo.equipment.35mm In article , "B.B. Bean" wrote: >On Wed, 6 Sep 2000 16:39:02 +0100, christoph manz wrote: > >>as others said, IR leaking doesn't seem to be a problem with most >>plastic tanks any more - or at least i had never any problems myself - >>anyway, there's one easy way to make sure that there's no fogging: >> >> ** process in a room with fluorescent lights ** >> >>of course you still have to load the film in complete darkness but once >>the tank has been closed it's safe to switch on the light as fluorescent >>tubes emit almost no IR. > >YIKES! In my experience, flourescents emit IR for several seconds after >turning them off. I have several rolls of striped film that taught me >this lesson the hard way. Some even manage to darkload under very dim fluorescent light....the same level of incandescent light would surely have fogged the film. -- Bye, Willem-Jan Markerink The desire to understand is sometimes far less intelligent than the inability to understand [note: 'a-one' & 'en-el'!]