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 21:22:45 -0400

On Monday, August 11, 2003, at 06:56  PM, Mark Dapoz wrote:

On Mon, 11 Aug 2003, whunter wrote:

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??

Ok, I've re-shot it using outdoor ambient light instead of the cheesy built in flash. If we need better results then I'll have to switch to using the OM's rather than this digital P&S. There is indeed a higher insensity of
yellowing in the centre than the edges.  Here are the results:

http://olympus.dementia.org/misc/55mm_yellowing_front.jpg
http://olympus.dementia.org/misc/55mm_yellowing_back.jpg

It's more obvious when looking through the rear, but you can see it both photographs. I'd say the yellowing is being caused by the glass and not
the coatings.

Mark -
Most interesting...... Certainly these images support the thesis of yaller within the glass of a convex element. From the posted picture I do not perceive a fall off in intensity from the center to the periphery to the extent expected, but expectations are empirical given the absence of thickness measurements. From the rear, the confines of a single(?( element is evident. The two white/light spots would be suspicious, but one is outside the perimeter of the affected element on the rear view. Probably the most effective would be for you to take a fairly strong loupe and examine directly for any focal defect within the perimeter of the yellow. Given the difficulty of photography with adequate magnification in this situation plus posting to the web, your first hand observation is needed. There should be a way to rig this lens to 'project' an image on a large white wall. That degree of magnification could be enlightening.

Despite all the sniping and quoting of extraneous texts on this issue, a good scientist asks the questions then searches for evidence to support or modify the hypothesis. My focus is on this group of Zuiko lenses produced in this time/technology frame. Extraneous and voluminous documentation of 'radiation effects on materials including glass', etc. are well known to those with experience in radiochemistry but will not provide the desired proof unless Olympus has published relevant data. Clearly (should I say 'yallerly'), your photos support involvement of a convex segment of the lens with extremely uniform changes within the glass. Radiation damage, chemically induced color change from either the rare earth ingredient or a contaminant or both remain equally suspect? The absence of any focal defects supports chemically induced color change. Short of more definitive chemical analysis, your photos support a non-destructive trial of 'sunlight' or other UV treatment. Again, if my lens, would remove the involved element for isolated Rx. If removed, a simple but definitive assessment can be made from the 'feel' of the lens surface. Is the surface smooth just like the other lens elements or rough like fine sandpaper. The latter would be consistent with radiation induced change in material structure; a smooth surface STRONGLY weighs towards chemically induced color change.
Will be interested in your results.
Bill


< 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