Go Back   Rangefinderforum.com > Cameras / Gear / Photography > Rangefinder Forum > Optics Theory -

Optics Theory - This forum is aimed towards the TECHNICAL side of photographic OPTICS THEORY. There will be some overlap by camera/manufacturer, but this forum is for the heavy duty tech discussions. This is NOT the place to discuss a specific lens or lens line, do that in the appropriate forum. This is the forum to discuss optics or lenses in general, to learn about the tech behind the lenses and images. IF you have a question about a specific lens, post it in the forum about that type of camera, NOT HERE.

Reply
 
Thread Tools Search this Thread Display Modes

Summicron Radioactive--Is this true?
Old 04-27-2010   #1
kkdanamatt
Registered User
 
kkdanamatt's Avatar
 
kkdanamatt is offline
Join Date: Jan 2008
Posts: 285
Summicron Radioactive--Is this true?

SUMMICRON

This lens was based on a Gauss design modified by Lee of Taylor and Hobson and known as the Cooke Opic lens. It was similar to Zeiss Ikon's Biotar and Sonnar lenses. It is a little known fact that when Summicron lenses were first
introduced they contained radioactive glass. You can identify some radioactive Summicrons by the fact the lens will have a red star engraved on its aperture ring.

Last edited by kkdanamatt : 04-27-2010 at 03:34.
  Reply With Quote

Old 04-27-2010   #2
Dave Wilkinson
Registered User
 
Dave Wilkinson's Avatar
 
Dave Wilkinson is offline
Join Date: Feb 2007
Location: Hull, Yorkshire, U.K
Posts: 2,281
Quote:
Originally Posted by kkdanamatt View Post
SUMMICRON

This lens was based on a Gauss design modified by Lee of Taylor and Hobson and known as the Cooke Opic lens. It was similar to Zeiss Ikon's Biotar and Sonnar lenses. It is a little known fact that when Summicron lenses were first
introduced they contained radioactive glass. You can identify some radioactive Summicrons by the fact the lens will have a red star engraved on its aperture ring.
mmm.....that rumour hasn't reached these parts yet!
  Reply With Quote

Old 04-27-2010   #3
kossi008
Photon Counter
 
kossi008's Avatar
 
kossi008 is offline
Join Date: May 2008
Location: Dresden, Germany
Age: 52
Posts: 927
I don't really know, but I think it's bogus.

First of all, the Cooke triplet, Biotar and Sonnar designs are similar to the Gauss design but, (a) they are not derived from it afaik, and (b) the Summicron is a double-Gauss. So I fail to see the relation between the Summicron and the aforementioned class of lenses.

Second, there have been quite some "radioactive" lenses in the 60s and 70s containing (correct me if I'm wrong here) Thorium Fluoride elements (e.g. the famed Canon FD 35mm f/2 SSC with concave fromt element), but (a) I fail to see what's the big deal here (other than novel optical properties at the time) and (b) I don't think the Summicron ever had that.

I could be wrong on some points, as I am not really an expert in Leica history. So maybe someone else will shed some more light on this?
__________________
Photon Counter
My flickr: http://www.flickr.com/photos/[email protected]/
  Reply With Quote

Old 04-27-2010   #4
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
The original Summicrons use Thorium Glass and they are radioactive. I own two of them. Summicrons with SN after 105xxxx do not use radioactive glass.

The original prototype Summicrons were marked as Summitars, and had the asterisk (or star) next to the name. I have only seen photographs.

http://www.imx.nl/photo/leica/lenses/lenses/page92.html

The Summar is a double-gauss, 6 elements in four groups, 1-2-2-1 configuration. The Summitar and earlier Summicrons are evolutions of it, 7 elements in 5 groups. The type 2 Rigid Summicron (black, the 70s version) was 6 elements in 5 groups. The modern Summicron went back to the 1-2-2-1 configuration.

Last edited by Brian Sweeney : 04-27-2010 at 03:52.
  Reply With Quote

Old 04-27-2010   #5
Chriscrawfordphoto
Real Men Shoot Film.
 
Chriscrawfordphoto's Avatar
 
Chriscrawfordphoto is offline
Join Date: Apr 2007
Location: Fort Wayne, Indiana
Age: 43
Posts: 8,962
THe very first collapsible summicrons did have radioactive glass, but it was changed to non-radioactive glass during the time the collapsible was made and no summicron 50 since then has had that glass. The radioctive ones are collectibles now.
  Reply With Quote

Old 04-27-2010   #6
kossi008
Photon Counter
 
kossi008's Avatar
 
kossi008 is offline
Join Date: May 2008
Location: Dresden, Germany
Age: 52
Posts: 927
I stand corrected. Just goes to show I don't know the first thing about summicrons... well well...

It's not even Thorium Fluoride, but Oxide. Shame on me.
__________________
Photon Counter
My flickr: http://www.flickr.com/photos/[email protected]/

Last edited by kossi008 : 04-27-2010 at 04:03.
  Reply With Quote

Old 04-27-2010   #7
Rob-F
Likes Leicas
 
Rob-F's Avatar
 
Rob-F is offline
Join Date: Mar 2007
Location: The Show Me state
Age: 78
Posts: 5,984
I think that the thorium was an impurity in what was intended to be a glass containing lanthanum. Later, Leica obtained supplies of Lanthanum not contaminated with thorium. A number of Leica lenses have been made with lanthanum glass, designated LAK-9 by Leitz.

Here's what I remember about the history of triplets and Summicrons. The first high-quality lens for photography was developed at Cooke optical, in England, by Taylor. The Cooke firm, having had no interest in producing it, licensed the design to Taylor, Taylor and Hobson (no relation to Mr. Taylor, the inventor of the lens). It became known as the Taylor-Hobson-Cooke Triplet: four elements in three groups, with the rear group being a cemented doublet. The Zeiss Tessar and the Leitz Elmar were both adaptations of this design.

Sometimes in the late 1800's, Dr. Paul Rudolph at Zeiss designed a very high quality fast lens having about six elements. He knew that the lens would have too many reflecting surfaces to be practical--too many internal reflections. He put his design into a file cabinet, where it remained until, after his death, the development of lens coatings made it possible to use Rudolph's design in practical photography. This was the Zeiss Planar and its derivatives, the Schneider Xenotar, Leitz Summitar, Summicron, etc.

I would be hard-pressed to say that the Summicron came out of work done at Cooke; though what I know is undoubtedly just the tip of the iceberg.
__________________
May the light be with you.
  Reply With Quote

Old 04-27-2010   #8
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
Thorium glass was used as it was a high index of refraction with low dispersion. It is a type of glass in and of itself, not an impurity of Lanthanum glass.

It will light up a Geiger Counter. The Thorium Summicron is unusual as the first element uses Thorium. Most other "hot glass" lenses use Thoriated glass in the interior. I keep a filter over my two. It is an Alpha Emitter.

Last edited by Brian Sweeney : 04-27-2010 at 16:15.
  Reply With Quote

Old 04-27-2010   #9
John Shriver
Registered User
 
John Shriver is offline
Join Date: Jan 2005
Location: Arlington, MA, USA
Posts: 1,225
Yes, my early Summicron definitely keeps the my Geiger counter excited. I tried bleaching it using a UV light, but it was UVC. Not the right wavelength at all.
  Reply With Quote

Old 04-28-2010   #10
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
A short explanation of Thoriated Glass by Oak Ridge.

http://www.orau.org/PTP/collection/c...cameralens.htm


Another interestig piece from the same site:

http://www.orau.org/ptp/collection/c...s/cloisone.htm

I'm going to think twice before buying Cloisonne jewelry from that antique store as a Gift!

Last edited by Brian Sweeney : 04-28-2010 at 04:05.
  Reply With Quote

Old 04-28-2010   #11
Alberti
Registered User
 
Alberti's Avatar
 
Alberti is offline
Join Date: Aug 2009
Location: Holland
Posts: 413
Quote:
Originally Posted by Brian Sweeney View Post
Thorium glass was used as it was a high index of refraction with low dispersion. It is a type of glass in and of itself, not an impurity of Lanthanum glass.

It will light up a Geiger Counter. The Thorium Summicron is unusual as the first element uses Thorium. Most other "hot glass" lenses use Thoriated glass in the interior. I keep a filter over my two. It is an Alpha Emitter.
Oh my, will this then expose the film?
Well, for me LOL, the amount of radiation will not be more than the background in many a house.
alberti
__________________
Nil camera, sed usus (after an emblematic text)
  Reply With Quote

Old 04-28-2010   #12
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
If you leave the lens, face down, on print paper in a darkoom; it will expose the paper.

It will not damage film in a camera.

Do not hit the glass with an axe or hammer. You do not want to inhale the debris.
  Reply With Quote

Old 04-28-2010   #13
Rob-F
Likes Leicas
 
Rob-F's Avatar
 
Rob-F is offline
Join Date: Mar 2007
Location: The Show Me state
Age: 78
Posts: 5,984
I have also read that in such lenses the rear element is made of leaded glass, to block radiation from reaching the film.

This (mis)information may very well be worth what you paid for it.
__________________
May the light be with you.
  Reply With Quote

Old 04-28-2010   #14
rxmd
May contain traces of nut
 
rxmd's Avatar
 
rxmd is offline
Join Date: Apr 2006
Location: Kyrgyzstan
Posts: 5,806
Quote:
Originally Posted by Alberti View Post
Oh my, will this then expose the film?
Well, for me LOL, the amount of radiation will not be more than the background in many a house.
alberti
I tried that with two Ektars once, an 178/f2.5 Aero Ektar and an 113/f4.5 Printing Ektar. Both are radioactive lenses. We put a 400-speed 4x5" negative in a changing bag and put the Ektars on top of the changing bag for 48 hours, both with the rear element towards the film. The film got fogged.

Since I'd expect a cloth shutter to be rather thinner than a changing bag, your film might get fogged, depending on which lens element is the thoriated one and on how long you leave the camera without advancing the film.
__________________
Bing! You're hypnotized!
  Reply With Quote

Old 04-28-2010   #15
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
Automatic Film Pre-Sensitization...

It's a Feature, not a Flaw!
  Reply With Quote

Old 04-28-2010   #16
John Shriver
Registered User
 
John Shriver is offline
Join Date: Jan 2005
Location: Arlington, MA, USA
Posts: 1,225
Well, lead glass is called "flint glass" when it's used in a lens, and it's been a key ingredient in optical design since the beginning. The front element of Summar and Summitar lenses is soft flint glass, that's why they are so commonly found scratched to hell.
  Reply With Quote

Old 05-02-2010   #17
Carterofmars
Registered User
 
Carterofmars's Avatar
 
Carterofmars is offline
Join Date: Sep 2009
Location: NYC
Age: 51
Posts: 772
Quote:
Originally Posted by Brian Sweeney View Post
Summicrons with SN after 105xxxx do not use radioactive glass.
Brian- are you sure about these serial numbers?

Thanks,

Joe
  Reply With Quote

Old 05-02-2010   #18
Brian Sweeney
Registered User
 
Brian Sweeney's Avatar
 
Brian Sweeney is offline
Join Date: Jan 2004
Posts: 14,912
I have two in the 104x range that use "hot glass". These lenses were original to Leica IIIf Black Dials. 105x was the cross-over point, and I would expect a couple to pop up- but have never seen one. I've seen some places state that only lenses with Sn under 1Million used hot glass, but know from first-hand experience that this is wrong.

The M-Mount lenses start in the 112x range, well-past the range that used Hot Glass. Personally, I find my later Summicrons in the 13x range to have improved coatings, and are terrific performers. I think this is a case of the lens being tweeked throughout it's production run.
  Reply With Quote

Old 05-02-2010   #19
Mackinaw
Think Different
 
Mackinaw is offline
Join Date: Mar 2005
Location: One hour south of the Mackinaw Bridge
Posts: 3,562
Quote:
Originally Posted by Brian Sweeney View Post
Do not hit the glass with an axe or hammer. You do not want to inhale the debris.
Bob Shell, when he was actively involved in photo forums, said that one reason thorium fell out of favor was because of the possible hazard to those who worked in lens manufacturing facilities. I guess making a lens can (or did) produce a lot of fine dust.

Jim B.
__________________
My fancy-schmancy gallery:
http://snowcountryphotography.com

My RFF Gallery:
http://www.rangefinderforum.com/phot...user=1453&sl=m
  Reply With Quote

Old 05-02-2010   #20
Matus
Registered User
 
Matus's Avatar
 
Matus is offline
Join Date: Jan 2008
Location: Frankfurt, DE
Posts: 1,843
That may well be true. Alpha radiation has range about 5cm in air and is very easy to shield (it does not penetrate a sheet of paper). But once the radioactive material finds its way in human body it causes heavy damage to the tissue its vicinity. On top of that half lives of alfa emitters are very long and these heavy elements tend to remain in the human body.

Often forgotten point is that the heavy elements (whether radioactive or not) are mostly very poisonous - so the befallen person will more probably suffer the chemical effect rather than radioactive ones.

I feel like I should get one too ...
__________________
________
Matus
... Flickr galleries: New Zealand , Spain
... per camera: Olympus XA , Jupiter J3 , Rolleiflex T, Mamiya 6, Ricoh GRDIII shots
  Reply With Quote

Old 05-02-2010   #21
rxmd
May contain traces of nut
 
rxmd's Avatar
 
rxmd is offline
Join Date: Apr 2006
Location: Kyrgyzstan
Posts: 5,806
Quote:
Originally Posted by Matus View Post
On top of that half lives of alfa emitters are very long.
There are some alpha emitters with a long half-life, but alpha decay doesn't mean long half-life all by itself. There are other alpha emitters with pretty short half-lives, such as Polonium-218 with a few minutes.

Of course those with the longer half-life are around longer. But that doesn't mean they're more dangerous, rather the opposite. The longer the half-life, the safer it is. If the half-life is longer, it radiates less. A material with a half-life of a few million years is much less hazardous than one with a half-life of five minutes. Thorium in optical glass, for example, is pretty harmless.
__________________
Bing! You're hypnotized!
  Reply With Quote

Old 05-02-2010   #22
CameraQuest
Head Bartender
 
CameraQuest is offline
Join Date: Mar 2005
Location: over the hills from Malibu
Posts: 5,697
Quote:
Originally Posted by kkdanamatt View Post
SUMMICRON

This lens was based on a Gauss design modified by Lee of Taylor and Hobson and known as the Cooke Opic lens. It was similar to Zeiss Ikon's Biotar and Sonnar lenses. It is a little known fact that when Summicron lenses were first
introduced they contained radioactive glass. You can identify some radioactive Summicrons by the fact the lens will have a red star engraved on its aperture ring.
Where did you get this quote from ?

Stephen
  Reply With Quote

origin of rumor
Old 05-02-2010   #23
kkdanamatt
Registered User
 
kkdanamatt's Avatar
 
kkdanamatt is offline
Join Date: Jan 2008
Posts: 285
origin of rumor

That information was forwarded to me from someone who knows someone, etc. who attends R.I.T.
  Reply With Quote

Old 05-02-2010   #24
CameraQuest
Head Bartender
 
CameraQuest is offline
Join Date: Mar 2005
Location: over the hills from Malibu
Posts: 5,697
Quote:
Originally Posted by kkdanamatt View Post
That information was forwarded to me from someone who knows someone, etc. who attends R.I.T.
OK, where did they get it?

Stephen
  Reply With Quote

Old 06-16-2017   #25
edwliang
Registered User
 
edwliang is offline
Join Date: Oct 2016
Posts: 63
Quote:
Originally Posted by Brian Sweeney View Post
Thorium glass was used as it was a high index of refraction with low dispersion. It is a type of glass in and of itself, not an impurity of Lanthanum glass.

It will light up a Geiger Counter. The Thorium Summicron is unusual as the first element uses Thorium. Most other "hot glass" lenses use Thoriated glass in the interior. I keep a filter over my two. It is an Alpha Emitter.
I have a summicron 50 LTM with s/n: 109XXXX. The front element doesnt show yellowish, but it lights up a emission counter, the figure is: 1.88 usv/h.

is it normal for Lanthanum glass to have emission? or i may have a thorium glass version of summicron?

thanks a lot.
  Reply With Quote

Old 06-16-2017   #26
HuubL
hunter-gatherer
 
HuubL's Avatar
 
HuubL is offline
Join Date: Mar 2006
Location: Netherlands
Age: 67
Posts: 2,360




__________________
Grain, not Noise!
My cameras
  Reply With Quote

Old 06-16-2017   #27
Rob-F
Likes Leicas
 
Rob-F's Avatar
 
Rob-F is offline
Join Date: Mar 2007
Location: The Show Me state
Age: 78
Posts: 5,984
Huubl, what is the serial number of this Summicron?
__________________
May the light be with you.
  Reply With Quote

Old 06-16-2017   #28
ckuwajima
Celso
 
ckuwajima is offline
Join Date: Sep 2016
Location: São Paulo, SP - Brazil
Age: 61
Posts: 148
Nice! What about the Geiger count at the rear of the lens?
__________________
Celso
Flickr
  Reply With Quote

Old 06-16-2017   #29
David Hughes
David Hughes
 
David Hughes's Avatar
 
David Hughes is offline
Join Date: Dec 2007
Posts: 7,461
Hmmm, but a lot of users of those lenses seem to have lived to a ripe old age...

Regards, David
  Reply With Quote

Old 06-17-2017   #30
HuubL
hunter-gatherer
 
HuubL's Avatar
 
HuubL is offline
Join Date: Mar 2006
Location: Netherlands
Age: 67
Posts: 2,360
Quote:
Originally Posted by Rob-F View Post
Huubl, what is the serial number of this Summicron?
The number of the lens is 1024500 - made around 1952.

The front element was pretty yellow, so yellow that it didn't need a yellow filter for increasing contrast

Only the front element radiates. The monitor doesn't count above background level when aimed at the rear.
__________________
Grain, not Noise!
My cameras
  Reply With Quote

Old 06-17-2017   #31
raid
Dad Photographer
 
raid's Avatar
 
raid is offline
Join Date: Nov 2005
Location: Florida
Posts: 30,607
So we are mainly talking about the collapsible Summicron. Right?
__________________
- Raid

________________


http://raid.smugmug.com/
  Reply With Quote

Old 06-17-2017   #32
HuubL
hunter-gatherer
 
HuubL's Avatar
 
HuubL is offline
Join Date: Mar 2006
Location: Netherlands
Age: 67
Posts: 2,360
Yes, well that was the subject that the OP launched-- ages ago. I'd be interested in other radioactive lenses though.
__________________
Grain, not Noise!
My cameras
  Reply With Quote

Old 06-17-2017   #33
ferider
Registered User
 
ferider's Avatar
 
ferider is offline
Join Date: May 2005
Posts: 11,250
Quote:
Originally Posted by HuubL View Post
Yes, well that was the subject that the OP launched-- ages ago. I'd be interested in other radioactive lenses though.
My only other LTM yellow lens is the Nikkor 35/1.8.

There are plenty of SLR fast radioactive 50s though. I have one left:



Roland.
  Reply With Quote

Old 06-17-2017   #34
ChrisLivsey
Registered User
 
ChrisLivsey's Avatar
 
ChrisLivsey is offline
Join Date: Jul 2007
Posts: 2,066
Interesting to resurrect this thread as the OPs second point on the star marking was never explored.
This link, Google Translate:
http://translate.google.com/translat...ag.htm&act=url

Details where the star was used for prototypes but goes on to show radioactive glass in several elements of a lens design with a rear flint glass plate to "protect" the film. Not that star being used to identify the radioactive lens.

There is also a discussion and picture of a Canadian 35mm Summilux with star engraving but on the focus ring and a very unusual type of star which does seem to be factory:

https://www.l-camera-forum.com/topic...ilux-red-star/
__________________
Fishing for shadows in a pool.
Louis Macneice

http://www.flickr.com/photos/red_eyes_man/
  Reply With Quote

Old 06-17-2017   #35
edwliang
Registered User
 
edwliang is offline
Join Date: Oct 2016
Posts: 63
according to what i have read on the internet, they use Thorium glass as front element only during the 1st year of summicron 50's production, that is 1952 (nr before 105 xxxx).

In 1953, they use Lak9 glass and not radioactive. My copy is 109 xxxx (1953), and it should be no emission. However, I tested it with a meter and there is a reading of 1.88~2.00 usv/h compared to normal background of 0.19 usv/h. This come out both from the front and back of the lens.

Anyone has tested summicron rigid, summaron 35 2.8 or other Leica Lanthanmum glass lenses?

regards
  Reply With Quote

Old 06-21-2017   #36
edwliang
Registered User
 
edwliang is offline
Join Date: Oct 2016
Posts: 63
sorry, i was wrong. English Chance Brothers' Thorium Based Glass was only used in Summitar*.

Summicron 50 has adopted Lak9 (thorium free)since its first batch production (from 993 xxx 1952). However, the first batch of Lak9 glass made in Wetzlar was 'experimental' and may contain small amount of thorium oxide.

here is the website which explains in very detail: http://www.marcocavina.com/articoli_...tro/00_pag.htm
  Reply With Quote

Old 06-29-2017   #37
HuubL
hunter-gatherer
 
HuubL's Avatar
 
HuubL is offline
Join Date: Mar 2006
Location: Netherlands
Age: 67
Posts: 2,360
Well, my 1952 Summicron is really hot! I'll check my Summitars later.



I decided to test my other 1952 Summicron with the GM-counter at work. The photos from top left to bottom right show:
1. the Leica IIIf RD-ST + Summicron
2. a close-up through the lens showing its yellow color
3. the background radiation: 1-2 cps
4. the radiation from the cron about 5 cm from the front lens: 40 cps
5. the radiation from the cron directly above the lens: 300 cps
6. the urban myth that a sheet of paper stops the radiation
7. even with the cap on radiation is detectable at 5 cm away: 30 cps
8. and immediately above the cap: 40 cps
9. and even through the rear, lens radiation still measures 10 cps.

I left my film in for 6 months. Will develop it later and show the results.
__________________
Grain, not Noise!
My cameras
  Reply With Quote

Old 06-29-2017   #38
leicapixie
Registered User
 
leicapixie is offline
Join Date: Jun 2011
Location: Toronto.Canada
Posts: 1,600
Many lenses in same period are radioactive.
I have a "newer" Collapsible Summicron that is safe..
I have a Pentax Takumar 50mm f1.4, 85mm f1.9 that yellowed.
A Canon 50mm f1.2 was highly radioactive!
I placed in darkroom, the lens on a piece of photographic paper.
After a week, I lifted lens and looked with safelight.
There was a dark mark size of lens element!
No need to develop!
Next step was sell and warn!
  Reply With Quote

Old 06-29-2017   #39
Bar8barian
Registered User
 
Bar8barian is offline
Join Date: Mar 2011
Posts: 179
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxx
__________________






  Reply With Quote

Old 06-29-2017   #40
mpaniagua
Registered User
 
mpaniagua's Avatar
 
mpaniagua is offline
Join Date: Nov 2011
Location: Tijuana, Baja California, Mexico
Age: 46
Posts: 1,075
My collapsible Summicron serial # is 1042919 and it does has some yellow tint (don't really mind, cause I use it on b/w only).

Thing is, when I use a collapsible lens on the IIIf of IIf (being Elmar, Summitar, Summicron or Summar), I normally carry it on my pants front pocket.


Should I be concerned about the radiation level from the lens? Any case for concern?

Best regards

Marcelo.
  Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 16:24.


vBulletin skin developed by: eXtremepixels
Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

All content on this site is Copyright Protected and owned by its respective owner. You may link to content on this site but you may not reproduce any of it in whole or part without written consent from its owner.