If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
http://www.orau.org/ptp/collection/c...cameralens.htm
-- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ |
#2
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
Recently, Nicholas O. Lindan posted:
http://www.orau.org/ptp/collection/c...cameralens.htm Looks like a good addition for a variation of Olgierd's collection... Neil |
#3
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
quite interesting ;-) I knew Playboy magazine was "hot", but not radioactively "hot" ;-) (http://www.orau.org/ptp/collection/c.../magazines.htm) thanks for the link, I'll add it to my radioactive lenses pages at http://medfmt.8k.com/mf/radioactive.html ;-0) regards bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
#4
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
It's interesting that this does not mention the earlier lenses that
contained thorium. I understand that Th has been used in optics at least since the 30s, and the AeroEktars (late 40s and early 50s) are famous for it. External radiation is almost entirely from gamma rays emitted by the daughter products of thorium decay. From the top of my head and looking at the formulation given, it would seem that there is significant self-absorption of gamma radiation in the lens itself. I wonder if that was taken into account in calculating the dose rates. In any case, the regulations have the force of law. I doubt if anyone has been harmed by normal use of these products. "Neil Gould" wrote in message link.net... Recently, Nicholas O. Lindan posted: http://www.orau.org/ptp/collection/c...cameralens.htm Looks like a good addition for a variation of Olgierd's collection... Neil |
#5
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
Is this possibly the reason why some older lenses are revered over their current
counteparts in that the hazmats they used to produce them then cannot be used anymore? Norman Worth wrote: It's interesting that this does not mention the earlier lenses that contained thorium. I understand that Th has been used in optics at least since the 30s, and the AeroEktars (late 40s and early 50s) are famous for it. External radiation is almost entirely from gamma rays emitted by the daughter products of thorium decay. From the top of my head and looking at the formulation given, it would seem that there is significant self-absorption of gamma radiation in the lens itself. I wonder if that was taken into account in calculating the dose rates. In any case, the regulations have the force of law. I doubt if anyone has been harmed by normal use of these products. "Neil Gould" wrote in message link.net... Recently, Nicholas O. Lindan posted: http://www.orau.org/ptp/collection/c...cameralens.htm Looks like a good addition for a variation of Olgierd's collection... Neil |
#6
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
"Nicholas O. Lindan" wrote in message hlink.net...
http://www.orau.org/ptp/collection/c...cameralens.htm Here's a site that illustrates the method for fixing these lenses: http://www.hermes.net.au/bayling/repair.html -Karl http://pages.cthome.net/karlwinkler |
#7
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
you might make such an argument, for example with the new eco-friendly glasses in the latest hasselblad superwide 38mm lens formula against the older ("enviro-bad") glass lenses, at least from careful inspection of the lens MTF graphs. But in actual shooting, it is probably hard to see these minor differences ;-) the other issue is that many of the "classic" lenses really were outstanding performers for their time. Unfortunately, direct comparisons against the latest glass and computer optimized designs would probably not be as favorable as against their (limited) competition of the past. Rodenstock as one example has some really stellar new APO ultrawide lens designs etc. On the other hand, the older lenses may be relative bargains for their level of performance (with a good example) given decades of inflation vs. today's better replacement optic prices ;-) I know the latest super angulons are better than my oldies, but I can afford my oldies and they are paid for, and used properly, they give surprisingly good results in many non-critical applications ;-) in short, I don't think the lack of certain toxic glasses means lenses can't be designed to some high level of performance today. It just costs more to do so. I think the winning sales design trend of the future will be to reduce the quality of lenses by nearly unnoticeable amounts while greatly reducing the costs. This has long happened with 35mm lenses, esp. prosumer zooms, and now with leica clone lenses (esp. wide angles..) thanks to various mfgers (cosina..). QGdeB and I have an on-going debate about this, but my blind lens tests convince me that most of us can't tell very good from superb lens performance, and our techniques and esp. film are limiting us rather than the lenses. Given that a 10% cut in lens performance in say resolution would cut lens costs by up to 50%, while not being noticeable in prints or on-film performance due to other limits (e.g., film), seems to me the way for future tradeoffs in MF camera/lens design? grins bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
#9
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
"Bob Monaghan" wrote
Karl, you might want to be careful about promoting that site, since it may encourage readers to destroy or discard their yellowed takumar lenses, when there may be a simple and non-destructive cure for their problems, viz. [sunlight gets the yellow out]. I'm confused: why would someone want to 'destroy' a yellowed lens. They may want to, in ignorance, get rid of a slightly radioactive lens, but sunlight won't remove the radioactivity. -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/ |
#10
|
|||
|
|||
Radioactive lenses - Oak Ridge Web site
well, the site clearly shows a humorous show of a guy destroying a yellowed takumar lens with a sledgehammer. The implication is that yellowed lenses are worthless, and only good for busting up or discarding. Per a number of posters, yellowed lenses may be clarified by UV/sunlight exposure. So people who visit the site, conclude that such lenses are useless and they might as well trash or bust them up, are possibly destroying optics which could easily be returned to service. That in my book is a dis-service to people who visit the site, and an understandable conclusion on their part based on what they see there, yes? ;-) A number of radioactive (thorium) lenses develop yellowing with time; it appears per some posters experiments that these lenses can also be rejuvenated and bleached by UV exposure. The fact that these are all older lenses, using organic adhesives (rather than the modern UV absorbing adhesives), makes this treatment at least worth the (near zero) cost of trying the sunlight exposure "fix"... hth bobm -- ************************************************** ********************* * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
New Leica digital back info.... | Barney | 35mm Photo Equipment | 19 | June 30th 04 12:45 AM |
[Survey] -Prime Lenses in the kit -results | Orville Wright | In The Darkroom | 69 | June 29th 04 02:38 PM |
Pentax "K" & "M" Lenses ? | Radio Man | 35mm Photo Equipment | 16 | June 23rd 04 10:23 PM |
Radioactive lenses - Oak Ridge Web site | Nicholas O. Lindan | Large Format Photography Equipment | 5 | May 23rd 04 04:44 AM |
Asking advice | Bugs Bunny | Medium Format Photography Equipment | 69 | March 9th 04 05:42 AM |