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01-28-2008, 06:26 PM   #1
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Getting rid of yellowing? How?

How would you get rid of yellowing on an old SMC takumar? Do you need to take it apart and clean it with some solution? I thought I'd read that you can get id of the yellowing by exposing it to light, or something, but I can't find where I read that now....




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01-28-2008, 06:47 PM   #2
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You got it...expose it to UV light like the sun.

Some people also say to cover the side away from the sun in tinfoil, but I have no experience with it.
01-28-2008, 06:49 PM   #3
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How about just using Manual White Balance, and see if it still effects your images.
You probably won't be able to tell then.
01-28-2008, 06:49 PM   #4
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QuoteOriginally posted by ryan s Quote
You got it...expose it to UV light like the sun.

Some people also say to cover the side away from the sun in tinfoil, but I have no experience with it.

Really? How long do you have to expose it for, and does it get rid of 100% of the yellowing?

Seems like magic.....



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01-28-2008, 10:10 PM   #5
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Here is one solution but I do not recommend it.

Brian Ayling's photographic repair tips
01-28-2008, 10:36 PM   #6
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But Wendy, some of those yellowed screwmount lenses are real gems.
Possibly not as nice as your estate sale 50mm f1.2, but still nice.

I don't use it often, but you'd have to pry my 35mm f2.0 from my dying hands.
It isn't yellowed, but it is well known for it
01-28-2008, 11:12 PM   #7
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QuoteOriginally posted by WendyB Quote
Here is one solution but I do not recommend it.

Brian Ayling's photographic repair tips
That just hurt to see that.......

01-29-2008, 12:51 AM   #8
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Ugh, I know exactly what that link is without even opening it. I would have even given him a case of beer for it

Well...I thought it was 2 weeks in the sun...? I would say just keep it there till it goes away.

01-29-2008, 02:12 AM   #9
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The Spotmatic Group Method

Here is the method we use on the Yahoo! Spotmatic group:

How to Cure Yellowing in Takumar 50mm f1.4 lenses.

Remove both lens caps and wrap the uncapped lens, except the rear element,
in aluminum foil and then set it on a windowsill that faces towards the sun.
Prop it up with something (like a rolled-up towel) so that it tilts in order
to get the most sunlight into it. Then go away and leave it.

A mild case takes about a week to ten days on a windowsill in California.
A severe one takes about a month.
The foil serves two functions. It reflects light off the lens body and
thus reduces heat buildup that otherwise would occur due to the black
finish on the lens and this could affect the lubrication inside the lens.
And by not capping the lens before wrapping it, light makes its way from
the back of the lens and reflects back off the foil at the front of the lens,
thus attacking the yellowing again.

This "sunlight cure" method has been successfully employed by a number of
members of the Spotmatic group and many 50mm f1.4 lenses which were
thought to be useless for colour photography have now been returned to
active service with "water clear" glass.
Some others have reported good results in about three weeks using an
ultraviolet light source.

The yellowing problem affects the Model II 50mm f1.4 Super-Takumars and all
other 50mm f1.4 lens through to the K-mount series.
The older Model I 50/1.4 Super-Takumars, the 8-element ones (which can be
distinguished by the protruding element at the rear NOT having a
protective metal rim), do not turn yellow because they do not have
the radioactive element, using an additional regular optical glass element to
get higher refraction instead. The Yellowing problem also affects the later
f2 35mm lenses with 49mm filters.
01-29-2008, 02:32 AM   #10
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QuoteOriginally posted by rayallen Quote
Here is the method we use on the Yahoo! Spotmatic group:

How to Cure Yellowing in Takumar 50mm f1.4 lenses.

Remove both lens caps and wrap the uncapped lens, except the rear element,
in aluminum foil and then set it on a windowsill that faces towards the sun.
Prop it up with something (like a rolled-up towel) so that it tilts in order
to get the most sunlight into it. Then go away and leave it.

A mild case takes about a week to ten days on a windowsill in California.
A severe one takes about a month.
The foil serves two functions. It reflects light off the lens body and
thus reduces heat buildup that otherwise would occur due to the black
finish on the lens and this could affect the lubrication inside the lens.
And by not capping the lens before wrapping it, light makes its way from
the back of the lens and reflects back off the foil at the front of the lens,
thus attacking the yellowing again.

This "sunlight cure" method has been successfully employed by a number of
members of the Spotmatic group and many 50mm f1.4 lenses which were
thought to be useless for colour photography have now been returned to
active service with "water clear" glass.
Some others have reported good results in about three weeks using an
ultraviolet light source.

The yellowing problem affects the Model II 50mm f1.4 Super-Takumars and all
other 50mm f1.4 lens through to the K-mount series.
The older Model I 50/1.4 Super-Takumars, the 8-element ones (which can be
distinguished by the protruding element at the rear NOT having a
protective metal rim), do not turn yellow because they do not have
the radioactive element, using an additional regular optical glass element to
get higher refraction instead. The Yellowing problem also affects the later
f2 35mm lenses with 49mm filters.
This is the true and right method. I saw the same type of post about 2 years ago on DPreview. Everyone thought the guy who posted the fix was nuts. It works and works well. Seems the coating on the tac is a little radio active and the UV rays of the sun have the affect and regenerate the radiation on the coating. You could also use a regular UV light and get the same effects. Good luck and let us know how it works out. I know you'll be shooting with a super lens in a few weeks.
01-29-2008, 04:13 AM   #11
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rayallen has it right. I had one a year ago and put it in the window without caps for 2 weeks and then turned it around for another 2 weeks. About 85% cured

But Little Laker is also correct. Just shoot in RAW and WB correct after you get home. You will never see the slight yellow tint in your shots.

If you aren't sure about WB adjusting, have a look at the following:

https://www.pentaxforums.com/forums/165310-post9.html
01-29-2008, 08:09 AM   #12
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UV cure the (very) fast way

QuoteOriginally posted by jsherman999 Quote
How would you get rid of yellowing on an old SMC takumar? Do you need to take it apart and clean it with some solution? I thought I'd read that you can get id of the yellowing by exposing it to light, or something, but I can't find where I read that now....




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Hello, jsherman999!

I resolved a pretty bad yellowing case of my SMC Tak 2/35mm last week. When I bought it the vendor didn't told me about this and in the test photos I mistake the tint as a white balance problem . I knew about the UV cure and a friend (electrical engineer) made for me a UV source (mercury lamp, about 80w of power, no UV filter). I put the lamp and the lens in a cardboard box (warning, this kind of UV is harmful for you - especially for the eyes!) and 15 hours latter (in 2 sessions) the lens was crystal clear. To be honest I saw the lens clearing from the first hours. The light is a tantalizing electric blue!

Specific condition: wrap the lens in alu foil (including between lens cap and front element), open to max aperture, distance about 2 inches (5 cm), rotate from time to time, cover the box with some fabric or alu foil to block uv and let the interior of the box cool. I got only minor warming of the lens but also a strong, bad odor in the room so keep it in a restricted area. When I'll get my K20D I will make for sure some test photos, and yes on my K100D the manual white balance trick worked pretty well.


Hope this helps you!
Radu

Last edited by RaduA; 01-29-2008 at 08:15 AM. Reason: I forgot about opening the aperture
01-29-2008, 08:44 AM   #13
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A word of caution to the home remedies though. Make sure you keep the lens as cool as possible. The lubricant from the focus ring will warm up and get on the aperture blades. When that happens, you will have a sluggish aperture and then looking at a $60+ pro cleaning.
01-29-2008, 01:27 PM   #14
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I am also in the process of doing this for a Takumar I have. The question I have is, will the yellow start coming back right away? If I leave it in the window for two weeks, take some photos and then it goes back in the bag for a few months, how rapidly does the yellowing come back?
01-29-2008, 02:29 PM   #15
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QuoteOriginally posted by RaduA Quote
I knew about the UV cure and a friend (electrical engineer) made for me a UV source (mercury lamp, about 80w of power, no UV filter).
Never mind - I realized that my air purifier has a UV lamp. I'll just have to stick my 50/1.4 in front of it!

Thanks for the hint.

Last edited by carpents; 01-29-2008 at 02:36 PM.
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