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07-25-2008, 11:17 AM   #1
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Question About Super Takumar 50/1.4

Hello, all,

Do the post-Super Takumar 50/1.4 lenses have yellowing of the glass, or is it just the Super Takumar (and earlier?) versions of this lens that have the radioactive substance and thus the yellowing of the glass? I have a Super Takumar 50/1.4, and it has moderately yellowed glass. Would a S-M-C or SMC 50/1.4 have yellowed glass? I am not sure if the radioactive substances were used in making these later versions, and so I thought I would inquire.

Thanks,
Glen

07-25-2008, 04:28 PM   #2
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07-25-2008, 05:46 PM   #3
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SMC: yellowing though hasn't had the years the Super has
07-26-2008, 06:49 AM   #4
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I thank you, Nesster. Your picture tells me exactly what I wanted to know.

Regards,
Glen

07-26-2008, 07:31 AM   #5
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Glen: FWIW, my S-M-C Takumar 50/1.4 arrived with moderate yellowing of the elements. Following the numerous internet references, I wrapped the lens in foil, placed it in a southern window sitting on the rear cap with the rear element angled to receive the most sunlight possible, and waited two weeks.

I was actually somewhat surprised to discover that the glass is water-clear now - this really works.

Last edited by monochrome; 07-26-2008 at 05:02 PM.
07-26-2008, 07:45 AM   #6
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I just put the super tak on the window sill with the foil. Will take a look in a week, maybe another ref shot vs. the SMC and the Auto, to document any progress. This is interesting.
07-26-2008, 08:42 AM   #7
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Super-Tak yellow elements

Hi Nester: FWIW, my S-M-C Tak was more like your SMC Tak. Your Super Tak is darker - so it might take a bit longer.

Then again, I did this in winter sun in Missouri - summer sun in NJ might be a different angle.

QuoteOriginally posted by Nesster Quote
I just put the super tak on the window sill with the foil. Will take a look in a week, maybe another ref shot vs. the SMC and the Auto, to document any progress. This is interesting.
07-26-2008, 03:25 PM   #8
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QuoteOriginally posted by Nesster Quote
I just put the super tak on the window sill with the foil. Will take a look in a week, maybe another ref shot vs. the SMC and the Auto, to document any progress. This is interesting.
Yes, please. I might even take a look at my super tak. Probably is a little dingy.

Bill

07-27-2008, 06:55 AM   #9
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Thanks, monochrome...

Did you have the front element or the rear element facing the sun? I have heard about the sun treatment and have thought about doing it with mine. Others, though, seem to like the warm tone the yellowed lens gives to b&w photographs.

Regards,
Glen
07-27-2008, 07:47 AM   #10
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Science of curing the Takumar Yellow Curse

QuoteOriginally posted by monochrome Quote
Glen: FWIW, my S-M-C Takumar 50/1.4 arrived with moderate yellowing of the elements. Following the numerous internet references, I wrapped the lens in foil, placed it in a southern window sitting on the rear cap with the rear element angled to receive the most sunlight possible, and waited two weeks.

I was actually somewhat surprised to discover that the glass is water-clear now - this really works.
Glen: I removed both lens caps and wrapped the lens in aluminum foil from the front element back to the very edges of the rear element. The purpose of the foil is supposed to be to reflect some sunlight back through the lens from front to back (double dose of sunlight), and keep the lens cooler (since the black paint would absorb heat) so the grease in the aperture blades doesn't melt.

QuoteOriginally posted by zx-m Quote
Thanks, monochrome...

Did you have the front element or the rear element facing the sun? I have heard about the sun treatment and have thought about doing it with mine. Others, though, seem to like the warm tone the yellowed lens gives to b&w photographs.

Regards,
Glen
Glen: I have a NOS SMC Y2 49mm filter I can supply you to duplicate the warm tone after you cure your lens . I did remove it from the packaging, but it is like new. I have a 52 still in the hang-card bubble packaging.

I arranged the lens so the rear element (open to the light) was pointed upwards and directly at the angle of the noon sun.

Here is a link to one of the first posts on this subject, at Asahi Optical Historical Club Yellow cast Follow the second link to the discussion of the radioactive isotope Thorium in the SMC coating on one element that causes the yellowing.

I have since read the UV rays in sunlight cause the cure, and that other sources of UV might also work. Here is a cached article from Pentax-Forums.com, but I could not link to it from a Google Search. PENTAX MANUALS

Here is Brian Ayling's cure for the Yellow Curse Brian Ayling's photographic repair tips (Not for the faint of heart where old Pentax stuff is concerned!)

Last edited by monochrome; 07-27-2008 at 07:54 AM.
07-28-2008, 06:40 AM   #11
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monochrome: I thank you for offering the Y2. I have the lens wrapped in foil, and sitting in front of a south-facing window. I gather most folks have air conditioning these days, and so the matter of opening and closing the window is not an issue. We live in an old house. I hope dust does not get into the lens, as the window will be kept open (as long as it does not rain).

Regards,
Glen
07-29-2008, 03:46 AM   #12
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Someone beat me to the de-yellowing documentation, and better / more thoroughly than I'd ever have

Manual Focus Lenses :: View topic - Super Takumar 50mm f1.4
07-29-2008, 01:15 PM   #13
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While on this topic: The other day I was using my most yellowed Takumar 50, it's fun looking through the viewfinder, like having on brown sunglasses... but interestingly the drug store scan restored white balance. Whadda ya know! (the tint probably loses close to 1 stop, based on a 1 stop ND filter I have)
08-03-2008, 09:20 AM   #14
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1 week update

The lens has been on a south facing windowsill for a week now. There were a couple of cloudy/rainy days mixed in... so I was curious as to progress.

A week ago (photo above) the Super was darker than the SMC. Now it looks lighter, or similar... depending on the angle etc. So progress has been good! I'm happy
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08-03-2008, 10:36 PM   #15
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Very interesting. I'll have to do this to my 50/1.4.
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