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tomas eichinger
12-Oct-2005, 12:30
I recently purchased a Linhof IV Technika which came with a Symmar 5,6/150mm. The lens has some fungus inside, nevertheless I love the image-quality despite that its very soft and has problems handling backlight situations. Thats why I purchased an additional lens on ebay and thought I will try out the famous Voigtlaender Apo-Lanthar 4.5 / 150mm and see what it's all about. I payed 550 US $ for a very clean lens which came in a Synchro-Compur shutter ... (maybe that was too much ? I am not very familiar with the value of vintage Voigtlander lenses). But when I inspected the lens I noticed that the front element has a serialnumber and the rear-element does not. Symmar lenses have the serial# engraved on both parts. Also the glass of the frontelement is perfectly clean but the rear shows several tiny airbubbles. Is it possible that the rearelement is not the original part ? Plus is there a way to figure out the age / production-year by means of the serial# ?

many thanks in advance for your comments

Bill_1856
12-Oct-2005, 13:09
It's important for the serial numbers of both elements of an "old" Symmar to match, but I can't think of any reason for the Lanthar to have a number on the rear element. Little bubbles in the glass was once the sign of high quality optical glass -- not to worry.
Please be sure to post your impression of the Apo-Lanthar lens (after you've used it for a while).

Ole Tjugen
12-Oct-2005, 13:54
The rear group of the APO-Lanthar contains the lens element that gave it its name. It is made of a glass containing Lanthanum. Most of these special glasses are rather tricky to make, requiring the glass to be just barely melted for a minimum of time. This automatically leads to the prescence of tiny air bubbles.

There are bubbles in my 150mm APO-Lanthar as well, and they don't harm the image quality at all. It's good - it's my favorite 150mm lens, and I own/have owned about 11 different ones.

The price you paid is good.

Michael S. Briggs
12-Oct-2005, 14:49
It's relatively uncommon for both front and rear cells to be labeled with a serial number. Don't worry about it.





Besides lanthanum, the high-index, low-dispersion glass used in the Apo-Lanthar also contains thorium. This makes the glass slightly radioactive and subject to discoloring with age. If you look carefully, you will probably notice a warm, or tea color to your lens. This can be mostly removed with exposure to UV light.
Today there are other high-index, low dispersion glasses that don't use thorium. There is more information about thorium glass on my Aero-Ektar webpage: http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html.

Mike Kovacs
12-Oct-2005, 15:07
For $550 you probably could have gotten a near new, multicoated 150mm set in a Copal shutter.

Steve Hamley
12-Oct-2005, 16:02
Mine is similar, late in Synchro Compur. It does not have a serial on the rear element.

$550 is a average price IMO. I paid about $100 less for mine with a sticky shutter that only needed a cleaning.

They have a wonderful character, like the Heliars from which they were derived. However, all of them seem to shoot "warm" if you shoot color; the yellow-orange cast is very noticeable. Some attribute this to the "browning" from the radioactive glass some of the Apo-Lanthars used, but mine does not show a cast and is not radioactive. I asked Jim at MPEX and he said all of them he's used exhibit that "warmness" - but they're great for B&W.

They also have little excess coverage on 4x5 though.

Steve

Scott Sharp
12-Oct-2005, 18:03
I too was fortunate that I found a late 150mm Apo Lanthar in a Compur shutter. Serial number is only on the front barrel not on the rear. I haven't shot any color with mine yet but what blk. & wht. polaroids I've shot have been sharp and contrasty even without a filter. Perhaps the slightly discoloured glass acts as a filter. You can do a Google search for "Age of Voigtlander Lenses " to be directed to a post with a list of Voigtlander serial numbers and dates. This is an invaluable resource. I dated my 180mm Collinear lens to 1900 and my 150mm Apo-Lanthar to 1965. As to your Symmar if you want a crisper image from that lens I would send it in to Paul Ebel for lens cleaning. My Symmar was hazy and produced lackluster images until it was cleaned. Just a thought. Enjoy both your lenses and your new Technika.

Michael S. Briggs
12-Oct-2005, 21:56
Steve, how do you know that your Apo-Lanthar is not radioactive?

Arne Croell
12-Oct-2005, 22:08
I'd like to chime in with Michael here. No discernible color cast does not necessarily mean it doesn't contain Thorium glass. It could either be a late model (what is the serial number, Steve?) or has seen a lot of UV to bleach the coloration. I had the chance to compare an early 1950's and a late 1960's version of the 210mm Apo-L. and both showed the same radioactivity, but the discoloration in the older one was much more pronounced. Btw, the lens element containing the Thorium and Lanthanum is the front element, not the back.

Ole Tjugen
13-Oct-2005, 00:11
Arne, that's strange.

Because when I took a Geiger counter to my lens, the rear group was clearly radioactive, the front not...

Arne Croell
13-Oct-2005, 08:50
Ole,

that is indeed strange. I did the very same thing with several Apo-Lanthars, and the Geiger counter showed the fronts to be radioactive. The front group is also the one that shows the discoloration. In addition, the patent shows the front lens as the one with the unusual (for the time) combination of refractive index and Abbe number.

Ole Tjugen
13-Oct-2005, 12:34
I'll check it again - and bring my Zeiss Planar as well (a very slight hint of warm tone discoloration might indicate a "special glass" element).

Michael S. Briggs
14-Oct-2005, 00:24
Here's my measurements of a 150 mm Apo-Lanthar. The front cell is very obviously tea colored. The measurements are one minute integrations with a Geiger counter. The background reading was 38 counts per minute. All of the measurements of the lens were made with a glass surface approximately 10 mm from the window of the Geiger counter.





Front surface of front cell: 13,990 counts. Rear (inner) surface of front cell: 886 counts. Inner surface of rear cell: 39 counts. Rear surface of rear cell: 25 counts.





The cross section diagram shows the five elements in two groups, with the first and last elements being positive. Clearly the front element is the radioactive one.





My guess is that all Apo-Lanthars use thorium glass. But there are lens models that have been redesigned to omit the thorium glass. Early Xenotars have thorium glass, late ones don't. The same for the 35 mm f1.4 Nikkor. This is based on radiation measurements I've made of a few samples. Color cast is only a clue and not definitive about the presence or absence of thorium glass.





And a link to a serial number table: Age of Voightlander Lenses at
http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004OCu.
The lens I measured has serial number 3,645,xxx -- the table says it is from 1954.

Arne Croell
14-Oct-2005, 08:52
Michael, thanks for the measurements., which are in line with what I have seen. I am still interested in Ole's remeasurement though.

As far as changes in the lens formulation go, there is a claim in the Vadenecum that Voigtländer changed the formulation in 1956 to a non-radioactive one. The "youngest" Apo-Lanthar that I had access to was a 210mm from 1966 according to the age table (a 6,xxx,xxx number) and that was as radioactive as the ones from the early 1950's, with a reduced discoloration (but still visible), which I would attribute to the 12 years difference in age. So if there was a glass change, it would have to be after 1966.

Steve Hamley
15-Oct-2005, 08:31
Michaael and Arne,

Sorry I dropped out of the thread for a while, my home DSL has decided to act like dialup, soon to be replaced. How do I know it's not radioactive? Well, I'm a senior health physicist (radiationprotection) and I have plenty of radiation detectors just sitting around. It's clear to me that thorium has not been intentionally added.

Steve

Arne Croell
15-Oct-2005, 10:31
Steve, the Thorium (as Thorium oxide) was put into the glass intentionally to influence the optical parameters (Abbe-number vs. refractive index). Lanthanum and Thorium glasses were a development from WWII; nowadays only the former are used, for obvious reasons. Thorium glasses were used in a variety of lenses sometime up to the late sixties/early seventies.

Arne Croell
15-Oct-2005, 10:34
Btw, Michael has a nice web site on the first lenses to use thorium glasses, the Aero-Ektars:

http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html

Michael S. Briggs
15-Oct-2005, 18:28
Arne, there have been cases of manufacturers redesigning lenses to replace thorium glass. Of the several Schneider Xenotars and 35 mm f1.4 Nikkors that I have measured, early ones are radioactive, and late ones are not, so I believe that there was a design change. As far as I know, the manufacturers didn't disclose the design change.

Arne's article in View Camera magazine has Voigtländer LF lens production ending in 1972, so the 1966 Apo-Lanthar that Arne measured as being radioactive is fairly late production. Steve, is your lens more recent (serial number table link above)?

Steve Hamley
17-Oct-2005, 05:21
I'll check the serial when I get home and post the date.

Steve

Steve Hamley
17-Oct-2005, 16:29
Mine's 6939xxx, which would date it about 1968?

Steve

Arne Croell
18-Oct-2005, 13:13
Thanks Steve! Have you measured (the front lens) whether it is hot? Since you mentioned you have the equipment at hand...
If its not radioactive, that would point to a changeover in the 1966/67/68 time frame.

Steve Hamley
18-Oct-2005, 15:38
Arne,

Neither is radioactive. I was surprised that they weren't.

But I will double check and post the results if I detect anything indicative of added radioactivity. I can also run a gamma spec on it (although I don't see any real reason to), thorium being rather easy to identify.

Steve

Arne Croell
18-Oct-2005, 15:46
Steve, I don't question your measurements. It just wasn't clear to me from the preceding posts, if you had measured already.
That clears up the interesting question when Voigtländer made the change, apparently about 5 years before they stopped production in 1972. Since the production numbers were much lower in their last years, most Apo-Lanthars out there will be radioactive, and only a few are not.

Steve Hamley
19-Oct-2005, 08:52
Arne,

Sorry for the confusion. I'm off today waiting for the cable guy to put in a new internet connection, and checked the lens with my home made geiger counter. Neither cell is radioactive.

Steve