Olympus-OM
[Top] [All Lists]

Re: Yellowing of radioactive lens elements....Re: [OM] 55/1.2

Subject: Re: Yellowing of radioactive lens elements....Re: [OM] 55/1.2
From: whunter <whunterjr@xxxxxxxx>
Date: Mon, 11 Aug 2003 15:16:14 -0400
Hate your yaller lens, but not me in my mailbox plez........

OK - - - Mark just supplied some info to a 'logic' question which woke me in the wee of the night. Let me present as "trying to find the answer without first asking the question is like reading in the DARK" - - or should I say "shooting through a yaller lens!!". Anyway, here goes:

Key Question:
1. Is the yaller primarily confined to the surface (coating, cement, dust, film, whatever) or is it primarily in the body of the glass? - McEwen: "Yes - cutting a section through the lens shows that the discoloration is homogenous throughout the glass, not restricted to the surface." - Conditions of this cut and method of examination to exclude surface effects not provided. (Anyone who has looked at 'flash glass' understands the issues.) - Dapoz provided some interesting data, but what does it mean in terms of cause and effect? Additionally, he provided an image through a yaller lens:
http://olympus.dementia.org/misc/55mm_yellowing.jpg
- Slow brain registered the image, but not the implications. Then........ cross examine this logic A. If yaller is primarily confined to the surface, the color should be reasonably uniform across any lens or element B. if yaller is primarily confined to the glass of a biconvex or plano-convex element, yaller intensity should be more intense in the center and fall off uniformly towards the edges C. if yaller is primarily confined to the glass of a biconcave element, the yaller intensity should form a ring at the periphery. - Somewhere in all this morass, believe someone posted a note that the yaller was confined to one element?? configuration of that element?? - Mark Marr-Lyon just provided some answers to the effect that it is most likely a single convex type element whence the glass thickness is greatest in the center.

Now Sports Fans........ Take another look at the image by Dapoz. (Mark - Can you shoot this again minus the distracting reflection in the center right where the answer may lie??) - I see, aside from the reflection, a disk of yellow with greatest intensity in the center and extremely uniform falloff to the periphery. If true, this would be consistent with uniform yallering of the glass of a convex element. (????) with insignificant contribution from the surface of the lens. i.e. If the surface contained the yaller, the entire yaller area would be uniform yaller intensity. No??

Maybe we are getting somewhere?? Now the next question is WHY? Is this primarily because of chemical coloration from a rare earth (something they are purposely employed to effect) or is it primarily glass degradation from ionizing radiation???? (Again, just because 'counter' activity is detected does not link radiation damage to the yaller.) One 'next step' thought in this regard. Yes, very uniform color changes proportional to the thickness of the glass (as the picture implies) could be rendered by radiation damage. But...... my limited experience in examination of radiation altered glassware suggests inhomogeneities are always present when the damage is from ionizing radiation (i.e. not chemical induced color change). Dapoz, can you acquire a magnified view of the central region of this lens image to look for 'bubbles' or other tiny focal defects characteristic of radiation damage???

And Sherlock said, "Watson, the answer often lies in what is missing rather than what you see."

Carry on...
Bill

On Monday, August 11, 2003, at 02:23  PM, Thomas Haegin wrote:

Out of curiosity I also put pretty much all my lenses
face-down on the little "light tablet" (tray) I have
for viewing slides.

These were the lenses I checked:

mm   f   S/N      Coat  Ring
---------------------------------------
50  1.8  136xxx   SC    Silver nose
50  1.8  887xxx   SC    Black nose
50  1.8  5.7 Mio  MIJ   Black nose
50  1.4  145xxx   SC    Silver nose
28  2.8  333xxx   MC    Black nose
100 2.8  202xxx   MC    Black nose

Here is what I found:

There was only one lens that actually was REALLY white
: the 50/1.8 with serial 887xxx. Interesting this was
my very first lens I obtained in 1979. It has always
been with me... no idea why it refuses to change
color.

The 50 MIJ had a slight tilt towards reddish and
warmer, as had the 100/2.8 MC.

The early 1.8/50 S/N 136xxx was darker/warmer than the
S/N 887xxx, but not as red/warm as the 100mm.

The 1.4/50 had a tilt towards greenish-greyish. With A
LOT OF goodwill one could see a little bit of yellow
in it as well. Certainly the taint on the 1.4 was
different in color than on the other lenses.

The 2.8/28mm was also warmer than white, about as the
100mm.

What does that all mean? I have no idea.

IMO we could probably ask all 200 members about their
600+ lenses and results will be all over the place...
This would show to me that Bill Hunter's assessment
that there are multiple factors, internal and
external, that contribute to changing the color of
glass must be quite correct, and yellowing is only one
possible variation among many.

I was quite surprised to see the differences so
clearly when putting them side-by-side. However, I
would not consider the color bias in any individual
lens as problematic. At least I never noticed
pronounced color shifts when looking at printed or
projected pictures of mine.

FWIW,
Thomas



 --- Mark Marr-Lyon <markml@xxxxxxx> schrieb: > Mark
Dapoz wrote:
Lens            Serial          Colour Cast
- ---------     -------         -----------
55mm f1.2       100584          severe yellowing
50mm f1.4       109257          minor yellowing
50mm f1.4       118622          minor yellowing
50mm f1.8       108622          no yellowing
50mm f1.8       114234          no yellowing
50mm f1.8       121253          no yellowing
35mm f2.8       103931          slight yellowing
35mm f2.8       108255          no yellowing
100mm f2.8      102159          slight yellowing

Very interesting!  My 35/2.8 with SN in the high
109k's doesn't show any yellowing either.  I would
be very curious to know if either the early 35/2.8
or 100/2.8 are radioactive too!

Mark


__________________________________________________________________

Gesendet von Yahoo! Mail - http://mail.yahoo.de
Logos und Klingeltöne fürs Handy bei http://sms.yahoo.de

< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >





< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >


<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz