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/

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

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*************************

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

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

"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

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*************************

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."

A number of users have reported being able to bleach out the yellow
discoloration of those pentax lenses by strong sunlight/uv - see gene
poon's posting (on "Sunlight vs. Yellow Peril: IT WORKS!") on my lens
faults pages at http://medfmt.8k.com/bronfaultsp.html pages for details,
quoting viz.:

From camera fix mailing list:
Date: Tue, 08 Apr 2003
From: "Gene Poon"
Subject: Sunlight vs. Yellow Peril: IT WORKS!

I just posted the following to the Spotmatic group. Perhaps some
members on camera-fix will find it useful:
---------------------------------------

About the experiment to see if sunlight would bleach Yellow Peril, the
radiation-caused yellowing of internal elements afflicting the
7-element 50/1.4 Super Takumar, Super-Multi-Coated TAKUMAR and SMC
TAKUMAR lenses for the Pentax Spotmatic cameras:

IT WORKS!

It has only been since Thursday, April 3 that I put two 50/1.4
Takumars on the windowsill. Since then, every day except Saturday has
been at least mostly sunny here in Northern California. Today I got a
bit impatient, and besides, I had to go into the box containing my
Pentax M42 stuff anyway, so I figured I may as well find out what was
happening and get out the rest of the 7-element 1.4 lenses to start on
them, if the sun bleaching was actually proceeding.

The experimental subjects were my very yellowest Super-Takumar and a
Super-Multi-Coated TAKUMAR which was moderately yellowed and had
filter ring damage and slightly stiff focusing. I figured I should
experiment with the two worst lenses, in case something bad happened.
The UNCAPPED lenses got completely wrapped in aluminum foil except
for the rear element, to reduce heat buildup in the sun, and also
because doing so would reflect light back through the lens, hopefully
attacking the yellowing from both sides.

This morning, after only five days, I unwrapped the lenses, and
compared the two experimental subjects with the rest of my 50/1.4
Takumars. THE SUN BLEACHING WORKS! The two experimental lenses are
now the least yellow (the comparison is not even close) of all my
50/1.4 Takumars except for the very early, 8-element Super Takumar
that is not prone to yellowing. Compared to that lens, and to the
55/1.8 and 55/2.0 lenses which also are not prone to yellowing, there
is still a slight tinge of yellow, about the same as the pink tone
from a weak skylight filter. They are being rewrapped for another stay
in the sun, and the rest of my yellow Takumars are going to join the
first two on the windowsill in a few minutes.

Probably many Pentax M42 collectors and users will have Takumars on
their windowsills, very soon if not already!

-Gene Poon

--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

"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/

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*************************