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12-22-2014, 11:07 AM   #16
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The small Ikea LED desk lights do work. They also have other uses, unlike a plain UV bulb (unless you have fish or reptiles). I've heard of people using them for macro photography as they produce a crisp white light and won't pose a fire risk if you drape a tissue over them as a diffusor.

I left mine on for about a week, with an old CD underneath to reflect the light back into the lens. It's not absolutely perfect but it's a lot less yellow than it was.

12-22-2014, 11:36 AM   #17
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QuoteOriginally posted by Dangermouse Quote
The small Ikea LED desk lights do work. They also have other uses, unlike a plain UV bulb (unless you have fish or reptiles). I've heard of people using them for macro photography as they produce a crisp white light and won't pose a fire risk if you drape a tissue over them as a diffusor.

I left mine on for about a week, with an old CD underneath to reflect the light back into the lens. It's not absolutely perfect but it's a lot less yellow than it was.
Some of the lenses have a natural warm tone (it seems) that will never go away, at least with a UV treatment. Others become cool. (Looking through the glass I mean, not image tint.) Sharpness is noticeably improved when you de-yellow a heavily yellowed lens -- definitely worth doing.
12-22-2014, 01:45 PM   #18
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The best comment I've seen on the Takumar glow was along the following lines:

"We don't mind so much when Aunty Flo has a warm glow in family portraits. We'd complain if she was blue or green!"

I've tried it since the treatment, the remaining yellow tone seems have negligable impact on the images.
12-05-2015, 08:22 AM   #19
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You could also create a camera profile with a Macbeth Color chart.

12-05-2015, 09:45 AM   #20
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QuoteOriginally posted by Clavius Quote
The atomic structure of the lens glass is altered by radiation from trace amounts of radioactive thorium in one rare-earth glass element, creating the yellowish-brown color; and this change is reversed by exposure to ultraviolet light.
Huh. I thought I read the Canadian Balsam glue between the rear couplet is what changes color (which is why you expose the rear to the UV light).

FWIW, I used the windowsill method to clear a yellowed S-M-C Tak 50/1.4. It took about 2 weeks and the lens is absolutely gin clear now.

Last edited by monochrome; 12-06-2015 at 09:15 AM.
12-06-2015, 08:45 AM   #21
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Great information posted here. I find the title very misleading: "Removing yellow tint from Pentax lenses".

Should be titled "Removing yellow tint from Takumar lenses"!!

Of course since I don't have any Tak's, I wouldn't have read this thread, if the title hadn't been misleading, I was wondering which Pentax's had the yellow tint!
12-07-2015, 05:04 AM   #22
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Given that they and their immediate successors are all made by Asahi Optical Co, they are honorary Pentax lenses.
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