M42 50mm SMC Takumar f/1.4 Yellowed - Light Source Suggestions?

jochen · Jan 8, 2013

After my experience the 1:2/35 SMC Takumar is more difficult to clear than the 1:1,4/50. There remains a certain light warm tone. If the 35 mm gets too hot there is a strong risk for delamination of the rear lens element. The 50 mm seems to be more heat resistant.

benjiboy · Jan 9, 2013

jochen said:
After my experience the 1:2/35 SMC Takumar is more difficult to clear than the 1:1,4/50. There remains a certain light warm tone. If the 35 mm gets too hot there is a strong risk for delamination of the rear lens element. The 50 mm seems to be more heat resistant.[/QUOTE

The Ikea Jansjo worklight http://www.ikea.com/us/en/catalog/products/20169658/ produces very little heat and works in removing the yellow caste on Thorium lenses like magic, and after you have removed it makes a very useful reading lamp all for less than $10.

fenderslash · Jan 10, 2013

My experiment has ended so I'll report the results. In the end I left it under the LED lamp for a few hours short of eight straight days. The lens is for all intents and purposes clear. I compared it side-by-side with an SMC Takumar 55mm f1.8 lens, which should have no yellowing, by looking through them both outside in broad daylight on a nice sunny day, and they were identically clear. All up I'd say it's a great success.

benjiboy · Jan 10, 2013

fenderslash said:
My experiment has ended so I'll report the results. In the end I left it under the LED lamp for a few hours short of eight straight days. The lens is for all intents and purposes clear. I compared it side-by-side with an SMC Takumar 55mm f1.8 lens, which should have no yellowing, by looking through them both outside in broad daylight on a nice sunny day, and they were identically clear. All up I'd say it's a great success.

Your uncle Ben told you it works .

fenderslash · Jan 10, 2013

Thanks uncle Ben

I suppose the main thing I can contribute to the thread is that I've proven that it doesn't have to be that particular Ikea lamp. All similar LED lamps probably work fine.

benjiboy · Jan 12, 2013

fenderslash said:
Thanks uncle Ben

I suppose the main thing I can contribute to the thread is that I've proven that it doesn't have to be that particular Ikea lamp. All similar LED lamps probably work fine.

True, but the Ikea Jansjo lamp cleared the yellow caste from my Canon FD 35mm F2 Thorium lens in forty eight hours, and it makes a very useful reading lamp afterwards.

bwinter88 · Nov 12, 2013

benjiboy said:
True, but the Ikea Jansjo lamp cleared the yellow caste from my Canon FD 35mm F2 Thorium lens in forty eight hours, and it makes a very useful reading lamp afterwards.

I was struggling to find an appropriate UV source.

Here in LA finding the sun is no problem. But it has been a tad cloudy lately.

Then I remembered a light fixture I have for video production. Ta-da!

The TruColor HS is a remote phosphor LED source that uses panels of phosphor excited by purely UV LEDs.

With the panels removed, 400W of UV light is bearing down on my lenses.

Any guesses how long it'll take to remove the yellowing? A day or two? 20 minutes?

digital&film · Jan 7, 2015

I got the Ikea light (from Amazon) and the yellowed Takumar 50mm 1.4 is near perfectly clear!

Damn.. a few days (and nights) with the light and it cleared up a lens that was yellowed to the point of 1.3 stops!

Thank you for whomever discovered this.

dynachrome · Jan 10, 2015

I will look for the Ikea lamp because I have a 28/2.5 MC Rokkor-X which is being serviced. Like my older MC Rokkor, it has darkened. I think the problem element is in a rear group. When the MC Rokkor-X comes back I will want to work on it. My earlier experience is with a 35/2 Canon FD SSC (1st version). That lens was kept under a CFL bulb with aluminum foil under it. It pretty much cleared the lens but took about five months. I later got another 35/2 FD SSC (2nd version) which is also a very good lens but which has no color problem. If I read the diagrams on the Canon Camera Museum website correctly the optical formula looks like that of the later 35/2 New FD, also a very good lens.

RalphLambrecht · Jan 12, 2015

zenrhino said:
Hi,

I have a yellowed SMC Takumar in M42 for my Spotmatic. I love the lens for b/w, but I want to shoot color with it and I find the yellowing drops probably a full half-stop from getting through the viewfinder (which at my age is increasingly a problem).

I could just set it out in the sun as such: (there was a url link here which no longer exists)

But, is there a better/faster way to get UV on it?

Thanks,

Clint

afacetanner will do a nice job.the window sill may take months

dynachrome · Jan 15, 2015

The IKEA lamp arrived yesterday and I picked up the 28/2.5 MC Rokkor-X this morning. Later today I will set everything up and see what happens. The lamp looks like it will be handy for other things too.

dynachrome · Jan 15, 2015

The aluminum foil is under the front of the lens and the lamp is about half an inch from the bottom of the lens. If this works I will find my older 28/2.5 MC Rokkor and give it the treatment too.

Zathras · Jan 16, 2015

dynachrome said:
The aluminum foil is under the front of the lens and the lamp is about half an inch from the bottom of the lens. If this works I will find my older 28/2.5 MC Rokkor and give it the treatment too.

Be sure to let us know how it works. I'm thinking of getting one of these to clean up a couple of yellowed Takumars.

dynachrome · Jan 17, 2015

About four hours to go for the 48 hour look.

dynachrome · Jan 17, 2015

After 48 hours under the lamp the 28/2.5 MC Rokkor-X is tremendously improved. There is a very faint cast left. Nothing like the dark yellow/green cast it started with. I compared it to a 28/2.8 MD and a 28/2.8 MD Celtic (last version). I've decided to put the lens back under the lamp for another two days and look at it again then. Now I can find the 28/2.5 MC Rokkor.

M42 50mm SMC Takumar f/1.4 Yellowed - Light Source Suggestions?

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