This is just plain wrong

xplus93 · 09-13-2014, 02:57 AM

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Asahi Pentax Super Takumar 50mm 1 4 M42 UV Cured for Yellowing of Thoriumelement 894948000402 | eBay

This really upsets me to see this. Somebody is permanently damaging a lens to make it "better". It's not even something excusable like changing the mount to work with a modern DSLR. The sad thing is I know a bunch of hipster with EOS rebel cameras are going to love this. Does anybody else think this is wrong or am I just being a whiny prick?

Stone G. · 09-13-2014, 03:12 AM

I am not quite sure, what the problem is?

It is a known fact that vintage lenses with thorium glass lens elements may yellow over time. This is due to the slight radioactive decay of Thorium (NOT dangerous for the user). The radiation will induce chemical changes to the cement bonding duplet lens elements together, (at least that is my understanding that the changes to the cement is the main cause of this yellowing).

It is also an established procedure to cure this yellowing by exposing the lens to UV-light of certain wavelenghts. You will find a lot of posts about "curing takumars" in this forum

So, no "bettering", only "curing".

.

AquaDome · 09-13-2014, 05:13 AM

I would be more concerned about the "proper coating for your chip" advice. I seriously doubt this round of "chicken-little-syndrome" was preceded by any actual scientific research.
Some people just don't have enough stuff to over-think.

vonBaloney · 09-13-2014, 07:05 AM

Originally posted by xplus93

Asahi Pentax Super Takumar 50mm 1 4 M42 UV Cured for Yellowing of Thoriumelement 894948000402 | eBay

This really upsets me to see this. Somebody is permanently damaging a lens to make it "better". It's not even something excusable like changing the mount to work with a modern DSLR.

They aren't damaging anything -- they are just returning them to the condition they ought to be in (i.e. clear glass, not yellowed). (At least if they do it right and aren't actually cooking them in the hot sun for 45 days. And it isn't just about the color cast -- it does make them sharper. I use an LED desk lamp jammed right into the lens and it only takes a day or so. (In other words, you can buy a yellowed one and fix it right up yourself quite easily.)

I agree that whatever he is saying about the coatings and the chip is dubious, or at least no reason to stay away from a lens.

digital029art · 09-13-2014, 08:01 AM

Mmmmm .. it's a tray of delicious Takumars! White chocolate is my fav!

stevebrot · 09-13-2014, 08:42 AM

Originally posted by vonBaloney

I agree that whatever he is saying about the coatings and the chip is dubious

I must remember to properly match my chips to my coatings.

Steve

**c.a.m** · 09-13-2014, 10:08 AM

Clearing (or 'de-yellowing') the lens does not damage it, provided the lens does not get overheated. I have cleared my own SMC Takumar 50/1.4 with a UV lamp and I'm absolutely delighted with its optical qualities.

However, despite the seller's apparent 100% positive feedback record and self-claimed credentials, I would shy away from this sale. The listing has a couple of self-inconsistencies (e.g., is it an 8-element or 7-element design?), and his narrative is odd. I'm not sure what is meant by "DSLM" and the comment on matching a lens coating with a camera "chip" is bizarre. Furthermore, there are no close-up images of the actual lens that is for sale.

- Craig

Last edited by c.a.m; 09-13-2014 at 10:18 AM.

**luftfluss** · 09-13-2014, 12:00 PM

Originally posted by c.a.m

Clearing (or 'de-yellowing') the lens does not damage it, provided the lens does not get overheated. I have cleared my own SMC Takumar 50/1.4 with a UV lamp and I'm absolutely delighted with its optical qualities.

However, despite the seller's apparent 100% positive feedback record and self-claimed credentials, I would shy away from this sale. The listing has a couple of self-inconsistencies (e.g., is it an 8-element or 7-element design?), and his narrative is odd. I'm not sure what is meant by "DSLM" and the comment on matching a lens coating with a camera "chip" is bizarre. Furthermore, there are no close-up images of the actual lens that is for sale.

- Craig

DSLM = Digital Single Lens Mirrorless.

Yeah, I'd shy away from this guy, too. Like you said, his narrative is odd.

johnyates · 09-13-2014, 12:04 PM

I think 'curing' a yellowed lens is a good idea. But I wouldn't buy from this guy. I have no way of knowing whether or not 25 days in the sunshine has melted the grease and fouled the aperture blades. And as mentioned above, he doesn't actually show you the lens. And, he can't differentiate between 'to' and 'too'.

The Tak 50 1.4 is a *great* lens--I'd encourage you to get one. . . .just not from this guy. They're pretty common and if you're patient can be had quite cheaply. If the one you buy has yellowed, by all means cure it. One benefit is that it'll get faster. That yellowing absorbs light.

Keep an eye out locally for people selling spotmatics as this lens is often included.

09-13-2014, 02:57 AM	#1
xplus93 New Member Join Date: May 2012 Posts: 14	This is just plain wrong Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. Asahi Pentax Super Takumar 50mm 1 4 M42 UV Cured for Yellowing of Thoriumelement 894948000402 \| eBay This really upsets me to see this. Somebody is permanently damaging a lens to make it "better". It's not even something excusable like changing the mount to work with a modern DSLR. The sad thing is I know a bunch of hipster with EOS rebel cameras are going to love this. Does anybody else think this is wrong or am I just being a whiny prick?

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09-13-2014, 03:12 AM	#2
Stone G. Pentaxian Join Date: Jun 2010 Location: North Zealand, Denmark Photos: Gallery \| Albums Posts: 1,516	I am not quite sure, what the problem is? It is a known fact that vintage lenses with thorium glass lens elements may yellow over time. This is due to the slight radioactive decay of Thorium (NOT dangerous for the user). The radiation will induce chemical changes to the cement bonding duplet lens elements together, (at least that is my understanding that the changes to the cement is the main cause of this yellowing). It is also an established procedure to cure this yellowing by exposing the lens to UV-light of certain wavelenghts. You will find a lot of posts about "curing takumars" in this forum So, no "bettering", only "curing". .

09-13-2014, 05:13 AM	#3
AquaDome Veteran Member Join Date: Jan 2014 Location: New Carlisle, IN Photos: Gallery \| Albums Posts: 1,475	I would be more concerned about the "proper coating for your chip" advice. I seriously doubt this round of "chicken-little-syndrome" was preceded by any actual scientific research. Some people just don't have enough stuff to over-think.

09-13-2014, 07:05 AM	#4
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by xplus93 Asahi Pentax Super Takumar 50mm 1 4 M42 UV Cured for Yellowing of Thoriumelement 894948000402 \| eBay This really upsets me to see this. Somebody is permanently damaging a lens to make it "better". It's not even something excusable like changing the mount to work with a modern DSLR. They aren't damaging anything -- they are just returning them to the condition they ought to be in (i.e. clear glass, not yellowed). (At least if they do it right and aren't actually cooking them in the hot sun for 45 days. And it isn't just about the color cast -- it does make them sharper. I use an LED desk lamp jammed right into the lens and it only takes a day or so. (In other words, you can buy a yellowed one and fix it right up yourself quite easily.) I agree that whatever he is saying about the coatings and the chip is dubious, or at least no reason to stay away from a lens.

09-13-2014, 08:01 AM	#5
digital029art Inactive Account Join Date: Jan 2011 Posts: 440	Mmmmm .. it's a tray of delicious Takumars! White chocolate is my fav!

09-13-2014, 08:42 AM	#6
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by vonBaloney I agree that whatever he is saying about the coatings and the chip is dubious I must remember to properly match my chips to my coatings. Steve

09-13-2014, 10:08 AM	#7
c.a.m Site Supporter Join Date: Jan 2013 Location: Ottawa, Canada Photos: Gallery \| Albums Posts: 4,191	Clearing (or 'de-yellowing') the lens does not damage it, provided the lens does not get overheated. I have cleared my own SMC Takumar 50/1.4 with a UV lamp and I'm absolutely delighted with its optical qualities. However, despite the seller's apparent 100% positive feedback record and self-claimed credentials, I would shy away from this sale. The listing has a couple of self-inconsistencies (e.g., is it an 8-element or 7-element design?), and his narrative is odd. I'm not sure what is meant by "DSLM" and the comment on matching a lens coating with a camera "chip" is bizarre. Furthermore, there are no close-up images of the actual lens that is for sale. - Craig Last edited by c.a.m; 09-13-2014 at 10:18 AM.

09-13-2014, 12:00 PM	#8
luftfluss Site Supporter Join Date: Jun 2011 Location: NJ Photos: Gallery \| Albums Posts: 11,627	Originally posted by c.a.m Clearing (or 'de-yellowing') the lens does not damage it, provided the lens does not get overheated. I have cleared my own SMC Takumar 50/1.4 with a UV lamp and I'm absolutely delighted with its optical qualities. However, despite the seller's apparent 100% positive feedback record and self-claimed credentials, I would shy away from this sale. The listing has a couple of self-inconsistencies (e.g., is it an 8-element or 7-element design?), and his narrative is odd. I'm not sure what is meant by "DSLM" and the comment on matching a lens coating with a camera "chip" is bizarre. Furthermore, there are no close-up images of the actual lens that is for sale. - Craig DSLM = Digital Single Lens Mirrorless. Yeah, I'd shy away from this guy, too. Like you said, his narrative is odd.

09-13-2014, 12:04 PM	#9
johnyates Pentaxian Join Date: Aug 2011 Location: Saskatoon, SK Photos: Albums Posts: 1,345	I think 'curing' a yellowed lens is a good idea. But I wouldn't buy from this guy. I have no way of knowing whether or not 25 days in the sunshine has melted the grease and fouled the aperture blades. And as mentioned above, he doesn't actually show you the lens. And, he can't differentiate between 'to' and 'too'. The Tak 50 1.4 is a great lens--I'd encourage you to get one. . . .just not from this guy. They're pretty common and if you're patient can be had quite cheaply. If the one you buy has yellowed, by all means cure it. One benefit is that it'll get faster. That yellowing absorbs light. Keep an eye out locally for people selling spotmatics as this lens is often included.