Takumar with yellow cast

xs400 · 01-20-2009, 07:22 PM

I might be able to get this Takumar 50mm f1/4 for a low price. But I am worried about the yellow cast on the lens. I'd appreciate any comments regarding the yellow cast - should I pass on this lens or is there an inexpensive way to get rid of the yellow cast.

Peter Zack · 01-20-2009, 07:34 PM

An often discussed issue. Common with this lens. I had one for a few years and partly cured the issue by putting the lens on a windowsill for 3 weeks and rotating it after 1.5 weeks. Wrapping the black body with aluminum foil to reflect heat (bad for the aperture blades) but leaving the caps off. The sunlight will partly and possibly totally clear the glass. It's due to radioactive elements used in the construction of the glass.

Cheap? Under $75.00 I would say.

**Vylen** · 01-20-2009, 07:58 PM

oh yea... that makes sense.. yellow = uranium... awasome

xs400 · 01-20-2009, 08:30 PM

Oh, it must be one of those radioactive Takumars. I'll see if I can get it for less than $20.

Thanks for the replies.

**rayallen** · 01-21-2009, 02:18 AM

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.
__________________

Peter Zack · 01-21-2009, 04:50 AM

It's a good lens and worthwhile owning. The glass element that affects the colour is made with Thorium oxide to reduce CA's and Pentax was not the only one that used this. Kodak, Nikkor, Canon, Yashinon and others used this method in some lenses. I think at some point (early 1970's??) this practice was banned.

There's an interesting article regarding the lens here:
My Favorite Lens

**Nick Siebers** · 01-21-2009, 06:15 AM

I have a yellow 35mm and a yellowish 50mm. I've had them under a CFL "black light" for about a week now, and I have seen some but not total improvement. If it doesn't work I will try sunlight once it warms up.

wildlifephotog · 01-21-2009, 06:33 AM

If you can put the lens in direct sunlight it will clear much faster. Window glass blocks a large portion of the UV light. I set ones I want to clear on the ledge outside the window. That way I can turn it as the sun moves.

Black light bulbs work very slowly for clearing the Tak lenses.

**ovim** · 01-21-2009, 01:04 PM

I have a yellowed Super-Multi-Coated takumar which I like a lot. I've been thinking about getting rid of the yellow tint but I'll have to wait for summer to get here.

I wonder has anyone opened the lens to speed up the process? I bought this lens in not so good shape and I took it apart to clear the elements. It wouldn't be too hard to take the rear element out again and put it under sunlight/UV-light if I knew it would be worth it.

**Nesster** · 01-21-2009, 01:11 PM

I've posted these before and after pics before, but let's see them again!

Before:

After:

The Super Tak in the before pic was by far the most yellowed. The after is the same lens, after a week on the windowsill in early summer, now much lighter than the control SMC. After another week it cleared even more.

Since then I did the SMC, as it was summer I'd put it out doors.

Now I kind of miss the yellowing and wish I hadn't done both!

**Vylen** · 01-21-2009, 01:47 PM

everyone should just get a black-light, or UV light... cause they're cool.... and you can burn your eyes with them :P

winglik · 01-21-2009, 02:24 PM

My Takumar 50mm 1.4 has the same issue, It's cold in NY, i put mine near the window, help a bit, but too cold to put the whole lens outside. Even with the yellow, still takes great picture with Auto WB. It just makes the view finder darker and harder to focus in low light.

Gooshin · 01-21-2009, 02:30 PM

i am currently doing the "black bulb" trick

its been 2 days, nothing substantial yet.

also, all of my "super takumar" lenses with the exception of the 135 f3.5 and 35 f3.5 show signs of yellowing, those being

the 55, 28, 35 f2 and 50 f1.4

the 35 being the worst of the bunch

also my 135 F2.5 has sslliiigh yellowing

but then again, so does my brand new cosina 55 f1.2, i think at some point its hard to discern between the coating and real yellowing.

HarryN · 01-25-2009, 12:18 AM

Interesting. If UV light is all it takes, and the heat is a problem, I can just rig up a UV LED to fix this. I play with LED lighting as one of my "other" hobbies, and unlike photography, I actually know what I am doing.

**Nick Siebers** · 01-25-2009, 08:22 PM

A black light incandescent bulb did squat for me, and others it appears via Google. Flourescent black lights seem to work better, but I haven't seen much change with a week of a compact flourescent. Then we had a few sunny days, and windowsill time seemed to make a much bigger change. an LED - who knows?

01-20-2009, 07:22 PM	#1
xs400 Pentaxian	Takumar with yellow cast I might be able to get this Takumar 50mm f1/4 for a low price. But I am worried about the yellow cast on the lens. I'd appreciate any comments regarding the yellow cast - should I pass on this lens or is there an inexpensive way to get rid of the yellow cast.

01-21-2009, 02:18 AM	#5
rayallen Site Supporter	How to fix yellowing 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. __________________

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01-20-2009, 07:34 PM	#2
Peter Zack Moderator Site Supporter	An often discussed issue. Common with this lens. I had one for a few years and partly cured the issue by putting the lens on a windowsill for 3 weeks and rotating it after 1.5 weeks. Wrapping the black body with aluminum foil to reflect heat (bad for the aperture blades) but leaving the caps off. The sunlight will partly and possibly totally clear the glass. It's due to radioactive elements used in the construction of the glass. Cheap? Under $75.00 I would say.

01-20-2009, 07:58 PM	#3
Vylen Site Supporter	oh yea... that makes sense.. yellow = uranium... awasome

01-20-2009, 08:30 PM	#4
xs400 Pentaxian	Oh, it must be one of those radioactive Takumars. I'll see if I can get it for less than $20. Thanks for the replies.

01-21-2009, 04:50 AM	#6
Peter Zack Moderator Site Supporter	It's a good lens and worthwhile owning. The glass element that affects the colour is made with Thorium oxide to reduce CA's and Pentax was not the only one that used this. Kodak, Nikkor, Canon, Yashinon and others used this method in some lenses. I think at some point (early 1970's??) this practice was banned. There's an interesting article regarding the lens here: My Favorite Lens

01-21-2009, 06:15 AM	#7
Nick Siebers Site Supporter	I have a yellow 35mm and a yellowish 50mm. I've had them under a CFL "black light" for about a week now, and I have seen some but not total improvement. If it doesn't work I will try sunlight once it warms up.

01-21-2009, 06:33 AM	#8
wildlifephotog Veteran Member	If you can put the lens in direct sunlight it will clear much faster. Window glass blocks a large portion of the UV light. I set ones I want to clear on the ledge outside the window. That way I can turn it as the sun moves. Black light bulbs work very slowly for clearing the Tak lenses.

01-21-2009, 01:04 PM	#9
ovim Site Supporter	I have a yellowed Super-Multi-Coated takumar which I like a lot. I've been thinking about getting rid of the yellow tint but I'll have to wait for summer to get here. I wonder has anyone opened the lens to speed up the process? I bought this lens in not so good shape and I took it apart to clear the elements. It wouldn't be too hard to take the rear element out again and put it under sunlight/UV-light if I knew it would be worth it.

01-21-2009, 01:11 PM	#10
Nesster Site Supporter	I've posted these before and after pics before, but let's see them again! Before: After: The Super Tak in the before pic was by far the most yellowed. The after is the same lens, after a week on the windowsill in early summer, now much lighter than the control SMC. After another week it cleared even more. Since then I did the SMC, as it was summer I'd put it out doors. Now I kind of miss the yellowing and wish I hadn't done both!

01-21-2009, 01:47 PM	#11
Vylen Site Supporter	everyone should just get a black-light, or UV light... cause they're cool.... and you can burn your eyes with them :P

01-21-2009, 02:24 PM	#12
winglik Senior Member	My Takumar 50mm 1.4 has the same issue, It's cold in NY, i put mine near the window, help a bit, but too cold to put the whole lens outside. Even with the yellow, still takes great picture with Auto WB. It just makes the view finder darker and harder to focus in low light.

01-21-2009, 02:30 PM	#13
Gooshin Pentaxian	i am currently doing the "black bulb" trick its been 2 days, nothing substantial yet. also, all of my "super takumar" lenses with the exception of the 135 f3.5 and 35 f3.5 show signs of yellowing, those being the 55, 28, 35 f2 and 50 f1.4 the 35 being the worst of the bunch also my 135 F2.5 has sslliiigh yellowing but then again, so does my brand new cosina 55 f1.2, i think at some point its hard to discern between the coating and real yellowing.

01-25-2009, 12:18 AM	#14
HarryN Forum Member	Interesting. If UV light is all it takes, and the heat is a problem, I can just rig up a UV LED to fix this. I play with LED lighting as one of my "other" hobbies, and unlike photography, I actually know what I am doing.

01-25-2009, 08:22 PM	#15
Nick Siebers Site Supporter	A black light incandescent bulb did squat for me, and others it appears via Google. Flourescent black lights seem to work better, but I haven't seen much change with a week of a compact flourescent. Then we had a few sunny days, and windowsill time seemed to make a much bigger change. an LED - who knows?