How long does it take to get rid of Takumar yellowing?

Started Oct 2, 2011 | Discussions
Raffwal
Raffwal Regular Member • Posts: 389
How long does it take to get rid of Takumar yellowing?

Hi. I recently bought one of the radioactive Takumars (50mm f/1.4 Super) and it's clearly yellow due to the thorium content. Well, I removed the caps and covered the lens in aluminium foil (obviously not the front lens area) like some people have advised not to warm the lens too much in sunlight. It's been now by the window for about ten days and it's clearly still yellow. Admittedly the windows here are triple glazed so they probably block much more UV than a single or double glazed one would. But I wonder just how long should the process take? I'm beginning to think that perhaps I should try to use some sort of an UV emitting lamp like some people have done.

And please, no links to the Australian way of dealing with yellowing Takumars. It was funny the first fifteen times.

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mrdc76 Regular Member • Posts: 379
Re: How long does it take to get rid of Takumar yellowing?

Raffwal wrote:

like some people have advised not to warm the lens too much in sunlight. It's been now by the window for about ten days and it's clearly still yellow. Admittedly the windows here are triple glazed so they probably block much more UV than a single or double glazed one would. But I wonder just how long should the process take? I'm beginning to think that perhaps I should try to use some sort of an UV emitting lamp like some people have done.

10 days is not enough. I kept mine in sunlight for 3 weeks and there was still some yellowing left. I wouldn't worry about the lens getting too warm unless you are keeping the lens in the window between the glass layers, as those areas tend to get very hot.

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Mikko

Peter Jonkman Regular Member • Posts: 116
Re: How long does it take to get rid of Takumar yellowing?

I have several yellowed taks, but I never took the time to de-yellow them. And it isn't even necessary on digital bodies; the auto WB takes care of any yellow color cast.

Raffwal
OP Raffwal Regular Member • Posts: 389
Re: How long does it take to get rid of Takumar yellowing?

Peter Jonkman wrote:

I have several yellowed taks, but I never took the time to de-yellow them. And it isn't even necessary on digital bodies; the auto WB takes care of any yellow color cast.

You know Peter, I actually thought that what a great B&W lens this makes with a built-in yellow filter!

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Peter Jonkman Regular Member • Posts: 116
Re: How long does it take to get rid of Takumar yellowing?

Raffwal wrote:

Peter Jonkman wrote:

I have several yellowed taks, but I never took the time to de-yellow them. And it isn't even necessary on digital bodies; the auto WB takes care of any yellow color cast.

You know Peter, I actually thought that what a great B&W lens this makes with a built-in yellow filter!

Hehe, indeed!

Do you also have a Spotmatic to put it on?

Raffwal
OP Raffwal Regular Member • Posts: 389
Re: How long does it take to get rid of Takumar yellowing?

Peter Jonkman wrote:

Do you also have a Spotmatic to put it on?

Unfortunately not. I'm actually planning to use my Taks on some EVIL camera, but am yet to decide which. Probably some NEX.

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brandrx Forum Pro • Posts: 28,337
Point the rear element towards the sun.

Point the rear element towards the sun.

The following link was done by forum member Shane Gerrish.

I tried it and it works.

Cheers.

Ron

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Raffwal
OP Raffwal Regular Member • Posts: 389
Re: Point the rear element towards the sun.

Thanks, Ron. I'll give it a try that way.

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KentG Veteran Member • Posts: 4,820
Re: Point the rear element towards the sun.

I don't know about the solar solution but I have used an old UV flourescent lamp designed for erasing EEPROM chips to do this and eliminate small cases of lens fungus (however it will come back if not cleaned properly).
Kent Gittings

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Peter Jonkman Senior Member • Posts: 1,007
Re: How long does it take to get rid of Takumar yellowing?

I've had the honor to optically disassemble my 50mm f/1.4 S-M-C Takumar this weekend (to clean it from fungus on several surfaces). I believe it's one of the rear elements indeed which is yellowed.

Doesn't the SMC coating block UV light also? The process could possibly be speeded up by simply unscrewing the back part holding the first element. No screwdrivers or special tools needed; just grab the black frame holding the first element and turn it counterclockwise. It comes off in one piece (with the last element). Now you can treat the two parts separately.

photominion
photominion Forum Member • Posts: 90
Re: How long does it take to get rid of Takumar yellowing?

I recently collected some old fifties among which I also have 3 radioactive lenses with yellow color cast.

Usually people recommend putting the lens out in the sun and waiting for several weeks for the color cast to go away.

I'm very impatient and was looking for a more efficient solution.

So I followed this tip here:

http://nortega.com/fastest-tool-to-clear-yellowed-thorium-lenses/

After only 2 days the light loss (1/4 EV darker before treatment) was gone and the color cast (+650K and +12 green tint before treatment) was cut in half.

I am testing this treatment on my more heavily impacted Fujinon and Pancolar lenses now. After that I will get back to the Takumar and see if I can get completely rid of the color cast.

I presented some results in my blog here:

https://mbphotox.wordpress.com/2015/07/22/color-tint-due-to-age-radioactive-decay-or-karma/

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RichRMA Veteran Member • Posts: 4,073
Re: How long does it take to get rid of Takumar yellowing?

If you can find a high power UV source, it might be done fairly fast.  But they cost a lot of money and most are not designed for continuous duty (UV microscope illuminators, etc).

solarider
solarider Veteran Member • Posts: 4,930
Re: How long does it take to get rid of Takumar yellowing?

It looks like the Ikea Jansjo led light is on sale in u.s. through july 28 for $6.99, you need to sign up for the Ikea Family, no cost. http://www.ikea.com/us/en/catalog/products/20169658/

or you can get it for close to three times the price on amazon

photominion wrote:

I recently collected some old fifties among which I also have 3 radioactive lenses with yellow color cast.

Usually people recommend putting the lens out in the sun and waiting for several weeks for the color cast to go away.

I'm very impatient and was looking for a more efficient solution.

So I followed this tip here:

http://nortega.com/fastest-tool-to-clear-yellowed-thorium-lenses/

After only 2 days the light loss (1/4 EV darker before treatment) was gone and the color cast (+650K and +12 green tint before treatment) was cut in half.

I am testing this treatment on my more heavily impacted Fujinon and Pancolar lenses now. After that I will get back to the Takumar and see if I can get completely rid of the color cast.

I presented some results in my blog here:

https://mbphotox.wordpress.com/2015/07/22/color-tint-due-to-age-radioactive-decay-or-karma/

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The Soul Hunter
The Soul Hunter Senior Member • Posts: 1,875
Re: How long does it take to get rid of Takumar yellowing?

Raffwal wrote:

Hi. I recently bought one of the radioactive Takumars (50mm f/1.4 Super) and it's clearly yellow due to the thorium content. Well, I removed the caps and covered the lens in aluminium foil (obviously not the front lens area) like some people have advised not to warm the lens too much in sunlight. It's been now by the window for about ten days and it's clearly still yellow. Admittedly the windows here are triple glazed so they probably block much more UV than a single or double glazed one would. But I wonder just how long should the process take? I'm beginning to think that perhaps I should try to use some sort of an UV emitting lamp like some people have done.

And please, no links to the Australian way of dealing with yellowing Takumars. It was funny the first fifteen times.

Window glass blocks pretty much all of the UV light. You need to either leave the lens where direct unfiltered sunlight can shine into it or put a UV lamp over it for a few weeks.

Holger Bargen Veteran Member • Posts: 4,888
Re: How long does it take to get rid of Takumar yellowing?

That's a surprise to me. I did not expect that an LED light source that is not especially designed for emitting UV light does have any part of UV within its light spectrum. LED light bulbs usually have very narrow spikes within their light spectrum. So if the IKEA lamp has UV it should be a problem for your health if you use it for what it was made for.

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Petroglyph
Petroglyph Veteran Member • Posts: 6,096
Re: How long does it take to get rid of Takumar yellowing?

The Soul Hunter wrote:

Raffwal wrote:

Hi. I recently bought one of the radioactive Takumars (50mm f/1.4 Super) and it's clearly yellow due to the thorium content. Well, I removed the caps and covered the lens in aluminium foil (obviously not the front lens area) like some people have advised not to warm the lens too much in sunlight. It's been now by the window for about ten days and it's clearly still yellow. Admittedly the windows here are triple glazed so they probably block much more UV than a single or double glazed one would. But I wonder just how long should the process take? I'm beginning to think that perhaps I should try to use some sort of an UV emitting lamp like some people have done.

And please, no links to the Australian way of dealing with yellowing Takumars. It was funny the first fifteen times.

Window glass blocks pretty much all of the UV light. You need to either leave the lens where direct unfiltered sunlight can shine into it or put a UV lamp over it for a few weeks.

Ordinary window glass passes 90% of 350nm (UVA) light through but blocks 90% from 300nm (UVB) and below.  So if UVA does the trick you can get it pretty much unfiltered through ordinary window glass.  If you need UVB most of that is blocked, so a lot of time in the window will be required.

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photominion
photominion Forum Member • Posts: 90
Re: How long does it take to get rid of Takumar yellowing?

You don't need any UV at all...

The IKEA lamp does not emit a measurable amount of UV (I checked, see my blog post about that) but it does emit more than 20 times the energy than the sun does in average over a day.

A high powered UV lamp will get the job done faster as long as its beam is focused on a small area.

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RichRMA Veteran Member • Posts: 4,073
Re: How long does it take to get rid of Takumar yellowing?

Nice to see all these "alternative illumination methods" (CFL, LED) the progressive-environmentalists push on us is also bad for the skin!

KentG Veteran Member • Posts: 4,820
Re: How long does it take to get rid of Takumar yellowing?

You need to find one of the small flourescent UV lamps designed for erasing EPROM chips about a decade or so ago. You can run those continuous for several hours. I have run them as much as 12 hours straight in those days. Most EPROM erasers these days are shielded units with trays for the chips so hard to use for lenses. A UV curing lamp should work OK also. A small fluorescent fixture and a good UV tube is what I used although it took longer than a dedicated eraser.EPROM erasers usually output UV light at around 237nm and like that what you are trying to do it put enough energy thru the glass that the captured electrons (Beta particles from Thorium decay) are freed up. Glass is one thing that will shield Beta particles by them losing energy and being absorbed by other elements in the glass. Paper blocks Alpha particles, glass blocks Beta particles, and lead is needed for Gamma rays, those being the 3 types of nuclear decay.

Kent Gittings

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RichRMA Veteran Member • Posts: 4,073
Re: How long does it take to get rid of Takumar yellowing?

KentG wrote:

You need to find one of the small flourescent UV lamps designed for erasing EPROM chips about a decade or so ago. You can run those continuous for several hours. I have run them as much as 12 hours straight in those days. Most EPROM erasers these days are shielded units with trays for the chips so hard to use for lenses. A UV curing lamp should work OK also. A small fluorescent fixture and a good UV tube is what I used although it took longer than a dedicated eraser.EPROM erasers usually output UV light at around 237nm and like that what you are trying to do it put enough energy thru the glass that the captured electrons (Beta particles from Thorium decay) are freed up. Glass is one thing that will shield Beta particles by them losing energy and being absorbed by other elements in the glass. Paper blocks Alpha particles, glass blocks Beta particles, and lead is needed for Gamma rays, those being the 3 types of nuclear decay.

Kent Gittings

And just for reference, any gamma-emitter that civilians are likely to encounter would be at least 90% attenuated by a 1/2cm of lead or so.  But, if you come across a cm cube of Cobalt-60...

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