De-Yellowing a Super Takumar

dixeyk

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I recently picked up a nice 50/1.4 and have a 55/1.8 (both yellow) so I decided to try and clear them up using the UV method. Since I live in WA state and it's Fall sunshine is in short supply so I picked up an 18" fluorescent black light and fixture at the local hardware store an am going to try the sunless method.

I'll check back in a few days to let you know how it's going.

Kevin
 

JoepLX3

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Yellow as in the plastic (or glass / optical result)?
- Sounds interesting, ensure to also include pre-photo's!!!
 

qball

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Will take about a 4=5 days depending on the severity of yellowing.

I did this with a 400 watt UV bulb (think dance club) and left my Hexanon 57mm/1.2 exposed for about 4 days and noticed a difference.
 

Brian S

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Yellow- as in radiation damage from Thorium used in the glass.

I left a lens under UV light for days, noticed an improvement. leaving in sunlight can get the lens hot and dry out the lubricants. UV did better.
 

BillN

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SMC Takumar lenses, (some - I cannot say all as I have not seen every lens), have a yellowish coating - you are not confusing it with this are you
 

Brian S

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The Takumar 50mm F1.4, in some versions, use Thorium Glass. It yellows from radiation. It is also very sharp with high color correction. The earliest 50/1.4's did not use it, and it was phased out later. But- many of the lenses from the 60s and 70s use Thorium, mine is one of them.
 

usayit

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Brian is correct. They are suppose to be clear and turn yellow because of the materials used for the optics were "unstable". I have quite a few SMC versions turning yellow. They are sharp and great optics... if you shoot B&W, the yellowing didn't really matter. Even in digital days, its fairly easy to correct in post.

It seems that UV treatment does work (although I have yet to do it myself). If you leave it out in sun exposure, it takes much longer and probably should wrap the lens in tin foil exposing just the front elements to offer some protection from the heat.
 

dixeyk

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actually...

As understand it, it is the rear element that yellows so I wrapped a 50/1.4 and an 55/1.8 that I have in tinfoil, exposing the rear element and sat them in front of fluorescent black light (no sun this time of year in WA state). In 2 days the 55/1.8 was dramatically clearer and the 50/1.4 (which was a bit yellower) was less so. I forgot to take a before picture but I'll set it up and snap a few pictures of the setup and the results.
 

JoepLX3

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Yeah, keep us posted, I am interested, also bought some old Pentax lenses...
 
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