[Jellygeist]

Much has been written about the SMC lenses tendency to yellow over time, thanks to the use of thorium, our radioactive friend.

Much has also been written about how to get rid of it. Sunlight is one way, the other is the legendary Jansjo LED lamp from IKEA, our Swedish retailer friend.

I have a fairly yellow (you'll see in the pictures) SMC lens. The yellowing is such that I've never been satisfied with the colours on the rolls I've run through it.

Instead of spending money on the Jansjo, my dad let me use some LED pot lights that he had lying around. They're actually the perfect size to illuminate the whole lens, and they were free, free, free. One hopes that the LEDs in these pot lights will have the safe effect as the ones in the IKEA lamp. Given how physics works, I'd imagine they will.

Pictures!

Here is how yellow the lens is:





Here is the "rig" I set up:





And here is the improvised body cap I made to protect the 6x7 while the lens is off it:





Yes, it all looks very stupid, and it is, but it was all at a cost of zero dollars. I'll probably leave it for a day and see if any progress has been made.

[Alex645]

Very cool. Do the LED lights give off high doses of UV? Because they are non-continuous light sources and strobe, I imagine it may take longer although I like how you put a mirror at the opposite end. Any reason you attached it to the rear instead of the front?

For your lens cap, Iʻd suggest using plastic wrap instead. Napkins are fine, but they arenʻt a 100% filter block and wonʻt stop the champagne from flowing into it.

Let us know how well this works and how long it took.

[Jellygeist]

Very cool. Do the LED lights give off high doses of UV? Because they are non-continuous light sources and strobe, I imagine it may take longer although I like how you put a mirror at the opposite end. Any reason you attached it to the rear instead of the front?

For your lens cap, Iʻd suggest using plastic wrap instead. Napkins are fine, but they arenʻt a 100% filter block and wonʻt stop the champagne from flowing into it.

Let us know how well this works and how long it took.

I have a feeling they don't put out much UV, but many other people have used LEDs for this purpose and it's worked for them, at least according to my Google searches, especially with the IKEA lamp (I'm sure IKEA is confused but appreciative of the niche that lamp has found). I heard about the mirror from other sources so I commandeered one from my mom. According to my sources, using LEDs should take about 24-48 hours to improve the yellowing.

I attached it to the rear because I couldn't get the lens to sit flat going the other way, what with the little pin that controls the DOF-preview sticking out of the rear of the lens.

I'm going to keep the camera body with the napkin filter in a dark, clean room while the lens is undergoing treatment. Far away from the gallons of champagne that is always flowing around here

Thanks for the encouragement! We'll see how this goes.

[tuco]

Good tip, thanks.

[Alex645]

I'm going to keep the camera body with the napkin filter in a dark, clean room while the lens is undergoing treatment. Far away from the gallons of champagne that is always flowing around here

You ARE a Jets fan, right? They made it to the second round!

I went to my first NHL game ever and it was a Jets game (in February). Mahalo nui loa to our book publisher Friesens in Manitoba for being such a great host during our press check. If youʻre ever looking for an excellent commercial or digital book printer, they are in your province.

[Jellygeist]

You ARE a Jets fan, right? They made it to the second round!

I went to my first NHL game ever and it was a Jets game (in February). Mahalo nui loa to our book publisher Friesens in Manitoba for being such a great host during our press check. If youʻre ever looking for an excellent commercial or digital book printer, they are in your province.

I'm a Jets fan insofar as I have to be in order to keep my life I'm glad they made it to the second round, though. Winnipeg is a rough place to be a lot of the time, so it's good that they have something to cheer about.

Where did you see the Jets play?

I looked up Friesens, and I was a bit flabbergasted that they are based in Altona of all places.

[Alex645]

I'm a Jets fan insofar as I have to be in order to keep my life I'm glad they made it to the second round, though. Winnipeg is a rough place to be a lot of the time, so it's good that they have something to cheer about.

Where did you see the Jets play?

I looked up Friesens, and I was a bit flabbergasted that they are based in Altona of all places.

The game was in Winnipeg. They lost to the LA Kings. I had been to the Bell MTS Place once before to see the minor league Manitoba Moose. Great atmosphere. Great fans. (I was raised in San Diego and have been a diehard fan, but regardless of the sport, the seats are always disproportionately filled with the visiting teams tourists. Home games feel like away games.)

Yes, Altona. Awesome mennonite community in the middle of nowhere just north of North Dakota. As neither Hawaii nor San Diego have an NHL ice hockey team, Iʻve adopted the Jets. My daughter went to college in beautiful Vancouver, BC, but as you know, Canuck fans have gotten a bad rep.

[Jellygeist]

The game was in Winnipeg. They lost to the LA Kings. I had been to the Bell MTS Place once before to see the minor league Manitoba Moose. Great atmosphere. Great fans. (I was raised in San Diego and have been a diehard fan, but regardless of the sport, the seats are always disproportionately filled with the visiting teams tourists. Home games feel like away games.)

Yes, Altona. Awesome mennonite community in the middle of nowhere just north of North Dakota. As neither Hawaii nor San Diego have an NHL ice hockey team, Iʻve adopted the Jets. My daughter went to college in beautiful Vancouver, BC, but as you know, Canuck fans have gotten a bad rep.

I haven't been to a Nu-Jets game even though Winnipeg is only a two hour drive. Tickets are expensive and hard to get unless you know somebody.

Manitoba must have been a pretty shocking transition from San Diego or Hawaii, especially in February. The temp extremes around here are crazy: insanely hot in the summer and insanely cold in the winter. You live where a lot of us who can afford it escape to in the winter.

I have not been to SD (my parents have, and they got me a Padres hoodie which I am wearing now even though I hate baseball) but I was in Hawaii in 2000 when I was ten or so. Quite enjoyed it.

[clickclick]

If your lights don't work, I have had success with this UV bulb that fits a standard light bulb socket. I've de-yellowed several lenses using it in a little clamp on type lamp with good success:

Fashion Outlet Ultra Bright E27 UV Ultraviolet 38LED Lamp Bulb 110V Color Purple Light - - amazon.com?tag=pentaxforums-20&

[Jellygeist]

If your lights don't work, I have had success with this UV bulb that fits a standard light bulb socket. I've de-yellowed several lenses using it in a little clamp on type lamp with good success:

Fashion Outlet Ultra Bright E27 UV Ultraviolet 38LED Lamp Bulb 110V Color Purple Light - - amazon.com?tag=pentaxforums-20&

Thanks for the tip! I think I should be able to source a UV LED lamp locally...I hope. How long did it take using the UV bulb?

I checked the lens about an hour ago and didn't notice too much change...it seems to me that the rear element is the one that's really yellow. I flipped it over so that the light is stuck onto the front of the lens. I'll flip it again in the morning.

[Alex645]

I checked the lens about an hour ago and didn't notice too much change...it seems to me that the rear element is the one that's really yellow. I flipped it over so that the light is stuck onto the front of the lens. I'll flip it again in the morning.

I do believe most thoriated elements were toward the rear, but I canʻt imagine why it would matter which direction the UV source is...especially with your mirror set-up.

When Iʻve de-yellowed thoriated Takumars in full tropical sun, it took many hours and many days.

[clickclick]

How long did it take using the UV bulb?

It's taken several days, but not continuous exposure, since I don't like leaving things like this turned on unattended too long. I sit the lens on a mirror like you show, and then shield the whole thing with tinfoil. I also will flip the lens end for end just to be sure there's as even an exposure as possible. Couple pictures attached - before, after, setup. The lens on the right is another Takumar that was already de-yellowed, and I included it for reference. The pictures were taken three days apart, so that gives us a time range. Wish they were better, but didn't put too much effort in it thinking I must be crazy to be documenting it in the first place.




.

[leekil]

The "after" pictures look significantly better, but I think it's hard to say because of the significant changes in exposure and white balance between the before and after.

[clickclick]

The "after" pictures look significantly better, but I think it's hard to say because of the significant changes in exposure and white balance between the before and after.

I agree totally on the white balance and exposure, and hence my comments when I posted on wishing I had better. I'd say look at the reference lens on the right for reassurance of what you see. I did shoot them RAW+ though, so I suppose I could go back and try to make some adjustments, but I was afraid I'd introduce a distortion in color and was better to just leave it as shot. What I can say is it really does work. If anyone wants a current "after" shot, let me know. I can certainly take another one.

[TomB_tx]

I've used about a 15" fluorescent "black light" tube stashed decades ago to clear Takumar lenses. I'd mount it about 2" above the lens with foil under the lens and leave it on 2-3 days, and the lenses cleared very well.