Vogtlander Petzval rear optical element dimensions

[Scott Davis]

https://dcphotoartist.files.wordpress.com/2020/08/video-1598313525.mp4?_=0

I have a friend in Colombia who just recently bought a Voigtlander nearly identical to the one I bought. His is missing the rearmost element in the rear group. He has someone who is willing to try and make him a new element, but he needs the specifications for it. Assuming it is the same as my lens (pictured below - they're only a few digits apart in serial number), mine looks to be an 11 inch f3.4 (I don't know what model number it is, because there's no model number marked on the barrel, just a serial number). I'd pull my rear element out to take measurements off of it but the retaining ring is completely stuck and I don't want to force it and damage something in the process.

Do any of you all know the formula and specifications for the rearmost element on such a beast? I'm sure they are public domain by now but I don't know enough to know how to find them. I've included the video of the lens he sent me so you can see exactly what he's looking for.

207080

My serial # is 16311. I believe his is 16631 or 16637. If someone has a reference to look those two lenses up by serial # and confirm exactly what they are, it would be even more appreciated!!

[karl french]

LOL. Good luck with that. Actually, I do have one of these as well (286mm f3.6) for which I swapped out the horrible front achromat for something better. I do have the rear air spaced pair from the donor lens still. I'll see if the rearmost element fits into the Voigtlander housing as well...

[karl french]

Nope. Too small.

[Scott Davis]

Nope. Too small.

Well, thanks for trying!

[karl french]

Happy to take whatever measurements your friend needs from my lens. You shouldn't worry too much about giving that retaining ring on top of the rear group a good hard twist. Put some dishwashing gloves on, get a good grip on the face of the retaining ring and twist. It's a stack inside with the inner most element proud of the lens carrier. The ring holds the stack in place.

[Steven Tribe]

Unfortunately, physical size ( diameter of lenses ) doesn’t identify the specific 1864 Petzval you (by proxy!) have!

Voigtlander was already making many versions of Petzvals (Speed/Focal length). For instance, the front lens with 79.3 mm diameter was made in versions with 214, 305 and 362 mm focal lengths (D’Agostini page 78).

Replacing a missing lens in any antique lens is a lost cause! Many have known radii and, sometimes, known refractive index, but there is no availability of original glass sources. Attempts to create replica Dallmeyer Patent Petzval lenses have used alternative glass designs to mimic the original lens effect, rather than replicate.

What might be possible is to replace the rear air-spaced group with another pair, taken from a scrap projection/photographic Petzval. It is no secret that Petzval Used the known balsam achromat as a basis for developing the combination with the innovative rear air cell. It could be argued that the Petzval design is such that any achromat from any maker - combined with a rear cell from another maker - would make a workable Petzval lens! I certainly have found that Petzvals made up from orphan achromat and orphan rear cells do produce OK images.

[karl french]

Yes, it's definitely better to try find a complete rear group that will fit the Voigtlander barrel. I'm surprised how good the image quality is on my hybrid Voigtlander 286.

[goamules]

"He has someone who is willing to try and make him a new element, but he needs the specifications for it."

The specifications for a petzval should be in lots of optical writings, it was a mathematical formula. But based on the refractive indexes of the two types of glass.

Is his person an optical engineer or manufacturer? Because if he wants to actually use the lens, not sell it to some sucker, the cost of making a rear group from scratch that is any good will be a lot more than the lens is worth. The sharpness of a lens with the rear made by a novice will be pretty suspect.

Voigtlander Serial No. 16673 it appears to be, if it every shows up on the market, buyer beware.

[Scott Davis]

"He has someone who is willing to try and make him a new element, but he needs the specifications for it."

The specifications for a petzval should be in lots of optical writings, it was a mathematical formula. But based on the refractive indexes of the two types of glass.

Is his person an optical engineer or manufacturer? Because if he wants to actually use the lens, not sell it to some sucker, the cost of making a rear group from scratch that is any good will be a lot more than the lens is worth. The sharpness of a lens with the rear made by a novice will be pretty suspect.

Voigtlander Serial No. 16673 it appears to be, if it every shows up on the market, buyer beware.

My understanding is that he wants to use the lens, not re-sell it. He's in Colombia- the optician (I think that's who's making the element for him) is in Brazil. I think the optician already has a blank of glass that's a reasonable approximation, and is willing to do it for the love of the exercise, rather than for profit, so he may be able to get it done at a cost-effective price. If he goes ahead and does it, I'll recommend to him that he includes some documentation in/with the lens to let people know the rear element was re-created.

[Steven Tribe]

Here are the best optical formulae Available for early Petzvals!

You can choose between various Voigtlander and others.

http://www.dioptrique.info/base/obj_1914/avant-1900.HTM

[Scott Davis]

Thanks for that! I'll pass it along.