The Standard Deviant
inanimated.co.uk
It will eventually stop when all the thorium atoms have decayed. You may wait a long time as the time for half to decay is about 14 billion years, then the next quarter is 14 billion years, then the next eighth is another 14 billion years, etc...
hans voralberg
Veteran
Damn there's no IKEA where I live, still very good info.
Roger Hicks
Veteran
Dear Hans,
There might be, sometime in the next in 14 billion years...
Cheers,
R.
Roger Hicks
Veteran
Dear Phil,
There are no unyellowed thoriated lenses, unless they've been bleached -- so bleaching one makes it MORE unusual in 2011. Why can't you buy a lens for the individual properties it had when it was new, instead of the individual properties (which many find undesirable) resulting from what amounts to an unforeseen design fault?
Cheers,
R.
maddoc
... likes film again.
... been here, done that.
Just to cure a slightly hazy Summitar lens that now shows heavy signs of element separation after the UV light destroyed the cement... :bang:
dogberryjr
[Pithy phrase]
I don't completely agree with this. I have a Canon 55mm 1.2 AL that is quite yellowed and I loved it for Kodachrome, especially with red subjects. Of course, now that's gone, so I'll have to try it out on some other stock. I may end up trying to clear it after all.
The Canon 58/1.2 used Thorium Glass. I did not know the 55/1.2 also used it. Most yellowing that people see in older lenses is from the Balsam yellowing.
Yellowing in the thorium lenses is much more extreme, looks like a Y1 filter. It is miserable with color film. Of course with Digital, you can try changing the white balance to Tungsten to fix it.
We had some lamps used for UV cured Epoxy. I'll have to find out what wavelength they are.
Yellowing in the thorium lenses is much more extreme, looks like a Y1 filter. It is miserable with color film. Of course with Digital, you can try changing the white balance to Tungsten to fix it.
We had some lamps used for UV cured Epoxy. I'll have to find out what wavelength they are.
dogberryjr
[Pithy phrase]
Jack Conrad
Well-known
Another thing about the yellowed lenses.
I've had a couple Takumar 50/1.4's and comparing a clear lens to
a yellowed one, the clear one was a full stop faster. At 1.4, given the same dim indoor lighting conditions my DSLR wanted to shoot at 1/30 with the clear lens and 1/15 with the yellowed one.
In other words, the yellowing reduces the amount of light reaching the film by a stop or possibly even more depending on how bad the yellowing has become.
So, by all means you'll be doing yourselves a favor clearing those great old lenses.
I've had a couple Takumar 50/1.4's and comparing a clear lens to
a yellowed one, the clear one was a full stop faster. At 1.4, given the same dim indoor lighting conditions my DSLR wanted to shoot at 1/30 with the clear lens and 1/15 with the yellowed one.
In other words, the yellowing reduces the amount of light reaching the film by a stop or possibly even more depending on how bad the yellowing has become.
So, by all means you'll be doing yourselves a favor clearing those great old lenses.
Roger Hicks
Veteran
Or indeed downright brownish, if you leave it long enough. I assume you have a pre-1950 Aero Ektar swilling around somewhere?
(Preferably not under the bed. Conversation between a friend and a third party: Third party, "How radioactive are they?" Friend, "Not very, but you wouldn't want to store them under the bed." Friend, reporting story to me: "He went a bit pale. He'd been storing five under his bed.")
Cheers,
R.
fates
Established
I have a made in Germany Wetzlar with a 24331XX serial. It's yellowing was very much like the Thorium (I've read Lieca denied using thorium, but then later admitted that they did) yellowing... actually, let's call it "monkey sh*t browning & dark clouding" so people don't confuse this process with removing desirable properties. A yellow or center filter is vastly superior to the decayed glass. Like others have said the discoloration will return. Might take a decade+ tho...
It cleaned up faster than a Takumar, but it is also 1/3 the surface area. 2 days of exposure and it is crystal clear again, there's no discoloration at all. I've only seen horrible results of Balsam sliding out, and this really looks... well looked like Thorium yellowing. Now I'm wishing I had documented the process this time.
I thought this was the fastest way: http://web.aanet.com.au/bayling/repair.html
Dear god, somebody please contact this bloke and tell him to revamp his website to not encourage people to:
- destroy the best still photo lenses that behave like cine taking lenses ever made. They have such great long barrel throws and are super smooth. As good as Zeiss Cine mechanisms.
- NEVER do this and poison themselves.
A Summicron with a serial number that late is well past the use of Thorium Glass. I have taken apart 8 or so of this series Summicron.
However: it is possible that the lens has radiation damage, depends what it was used for in the past. I've locked cameras into a vacuum chamber with radioactive elements before.
However: it is possible that the lens has radiation damage, depends what it was used for in the past. I've locked cameras into a vacuum chamber with radioactive elements before.
JFH
Established
Not to divert the OP's original intent, but for my MC Rokkor 28mm f2.5 SI lens with a yellow/brown internal element, I found that simply screwing on an 82A filter seems to restore good color performance... and it's really fast, goes on in less than 15 seconds...
charjohncarter
Veteran
What kind of bulb is in the IKEA lamp?
sevo
Fokutorendaburando
It looks very much like a Seoul P4 LED.
charjohncarter
Veteran
Thanks.....
fates
Established
The bulb is pretty much encased in the lamp, and I can't see a quick way to pull it out and read any markings.
Yeah, I was surprised to see a rigid 1970 lens that appeared to have Thorium "Monkey Sh*t Browning", but I figured I was new to Leica glass ownership... and what I don't know can fill an 80 gallon drum. I'll post back in another ten years and let everyone know how the discoloration is proceeding.
I was so apt to clear it up, I didn't think too much of it's possible odd nature, and in retrospect should have documented the process. :bang:
Sure, if you like loosing light, can't stand to put the camera down for 6-12 hours (or attach another lens in the interim), or part with the 5.99 USD for a lamp...
Wow, I thought most shooters liked their glass clear, non-tinted, and as fast as it was designed to be?
Yeah, I was surprised to see a rigid 1970 lens that appeared to have Thorium "Monkey Sh*t Browning", but I figured I was new to Leica glass ownership... and what I don't know can fill an 80 gallon drum. I'll post back in another ten years and let everyone know how the discoloration is proceeding.
I was so apt to clear it up, I didn't think too much of it's possible odd nature, and in retrospect should have documented the process. :bang:
Not to divert the OP's original intent, but for my MC Rokkor 28mm f2.5 SI lens with a yellow/brown internal element, I found that simply screwing on an 82A filter seems to restore good color performance... and it's really fast, goes on in less than 15 seconds...
Sure, if you like loosing light, can't stand to put the camera down for 6-12 hours (or attach another lens in the interim), or part with the 5.99 USD for a lamp...
Wow, I thought most shooters liked their glass clear, non-tinted, and as fast as it was designed to be?
fates
Established
Originally Posted by hans voralberg 
Damn there's no IKEA where I live, still very good info.
Roger,
I just wanted to say this was one of the funniest posts ever... at least to me. Really cracked me up!
Damn there's no IKEA where I live, still very good info.
Roger,
I just wanted to say this was one of the funniest posts ever... at least to me. Really cracked me up!
ampguy
Veteran
yes, this is correct
yes, this is correct
This was my reason for deciding against an old Pen 38/40/42 lens as they will give a brown cast to the images unless cleaned of the light.
I have a low power UV laser, but it's not powerful enough to clean a lens, but is useful for being able to tell if a vintage lens is blocking UV light or not.
yes, this is correct
This was my reason for deciding against an old Pen 38/40/42 lens as they will give a brown cast to the images unless cleaned of the light.
I have a low power UV laser, but it's not powerful enough to clean a lens, but is useful for being able to tell if a vintage lens is blocking UV light or not.
michel v
Member
Hello,
I bought this very lamp yesterday and have let my Takumar 50 1.4 bask in its light for over 20 hours.
I really should have taken accurate pictures of the lens before the process, because I'm not sure that it was actually bleached when I look at it now.
Just in case, would a serial number of 1725xxx still fit with the period when they used thorium?
Or is shining LED light in it useless?
Thanks.
(And I just noticed my Pen F 40mm is a little bit yellow too. Did every lens in this serie use thorium?)
I bought this very lamp yesterday and have let my Takumar 50 1.4 bask in its light for over 20 hours.
I really should have taken accurate pictures of the lens before the process, because I'm not sure that it was actually bleached when I look at it now.
Just in case, would a serial number of 1725xxx still fit with the period when they used thorium?
Or is shining LED light in it useless?
Thanks.
(And I just noticed my Pen F 40mm is a little bit yellow too. Did every lens in this serie use thorium?)