An interesting posting on the cameramakers list. I hope it's not bad
netiquette to forward it to here.
-----Original Message-----
From: cameramakers-admin@xxxxxxxxxxxxxxxxxx
[mailto:cameramakers-admin@xxxxxxxxxxxxxxxxxx] On Behalf Of Kelvin
Sent: Wednesday, 9 April 2003 9:06 PM
To: cameramakers@xxxxxxxxxxxxxxxxxx; NikonRepair@xxxxxxxxxxxxxxx;
camera-fix@xxxxxxxxxxxxxxx; camera-fix@xxxxxxxxxxxxx
Cc: Charles_Lau@xxxxxxxx; Parlin 44; Lieu WL; ClubM42@xxxxxxxxxxxxxxx
Subject: [Cameramakers] Sun bleaching yellowed lenses
Hi guys,
this may be of interest to some of you who have yellowed lenses ... for
me,
besides my super-takumars it is my nikkor 35/1.4 pre-AI. Apparantly you
can
wrap your lens in foil, front cap on, and face the rear element to the
sun for
a week and it reduces the yellowing (if not eliminate it).
I attach the post. This is an exciting development.
Gene: If you're on the list... maybe you can elaborate..?
Message: 1
Date: Tue, 08 Apr 2003 09:03:42 -0700
From: Gene Poon <sheehans@xxxxxx>
Subject: Sunlight vs. Yellow Peril: IT WORKS!
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
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