Dallmeyer "D" f/6 Patent Portrait Lens - Petzval or not ?

[CCHarrison]

Tuant,

I am just finishing a 23 page article on Petzval lenses and can tell you that historians and manufacturers dont define Petzvals by a flat or convex back lens. As soon as my article is published, I can share the information with you. Petzvals are typically defined as a cemented doublet in the front (crown in front, flint in back), derived from a telescope objective, with a rear, air spaced, component - originally, flint followed by crown. The precise curves of these elements dont define the Petzval design. Dallmeyer, with the PP lenses, went on to flip the rear component so it went crown-flint and he also altered the curves. Still a Petzval. In fact, Kingslake mentions that the order of the rear elements doesnt matter much at all in terms of performance.

Dan

[goamules]

In the shooters world, there is a big difference. Everyone wants to know if the back is flat or convex to decide if the lens is worth certain money. I am still not sure if we can call the other kind a Petzval, at least I won't if I want to sell a PP design lens on Ebay some day. This could get you in trouble with an angry buyer demanding for refund I decide the value of a lens based on that too myself. So maybe we should call the flat-flinted ones "traditional Petzval" instead? I think there should be a difference, otherwise, this could be a very chaotic world. Anyways, the feel and degree of softness can be very different between a traditional Petzval and a PP design. I am curious to see how others would respond to this when they wake up this afternoon. This debate may help right some wrong on Ebay for the Petzval confusion out there. No matter what people decide to name here in the end, I would never call a PP design lens a Petzval lens if I am selling such a lens on Ebay! You are just asking for trouble with 99% of the buyers.

Tuant

I think we better let Tuant keep thinking the sky isn't blue too. I've sold hundreds of lenses, and several Dallmeyer D's including a 5D. I've never heard of anyone asking "how flat is the glass", most buyers barely know the rear should be airspaced. I'm contacted weekly by people wanting to buy Petzvals. Not once, ever, have I heard this discussed. Dan and I associate with a LOT of lens experts, worldwide, for years. Dallmeyer Ds were, are, and always have been a Petzval design. The reason they sell for less is they are an f6 group speed, not the cultish F3.

The Petzval design was adjusted many times, from Lerebours in the 1850s, to Ross and Dallmeyer in the 1860s, to Wollensak in the 1910s. Slight adjustments and optimizations, but the basic design is like no other, they're all Petzvals.

Tuant, if you think the Dallmeyer Patent Portrait lenses are not Petzvals, you are talking about all of them, The A, B, and D series. So a 3B isn't a Petzval either? But you are going against what both Dallmeyer said and what lens scientists know. See page 384 of Lens Design Fundamentals
By Rudolf Kingslake, R. Barry Johnson. Or his A History of the Photographic Lens:

"The Dallmeyer Patent Portrait Lens - In the design of a portrait lens of the Petzval type, it is immaterial whether the crown or flint element in the rear component comes first." And he mentions that thickness, thinness, curves and flatness vary with each manufacturer.

[tuant]

Well, Garrett, there are azure, light, dark blue and so on. We guys have never been good with colors as long as Eddie doesn't all of a sudden start offering me lots of "petzvals" lenses, I am all right with it. Checking in eBay, we can see that most stick to this flat-glinted rule, or we will see so many more petzvals under petzvals on eBay. We LFers just need to take a quick look or hear the exact wording on a lens with no confusion at all. I have a chevalier which I will not call it a petzval even though he is the godfather of all petzvals. I am curious to see what others have to say, especially Eddie, the future safety of his garage is in question here

From tuant's iphone

[goamules]

deleted....ah...skip it.

[CCHarrison]

Chevalier the godfather of Petzvals ? Not even close. First, he mistakenly thought Petzval copied his design (not true). Second, he tried to suggest his L'Objectif Double ou à Verres Combinés was superior for portraits to Petzvals design (not true). Chevalier reluctantly made Petzvals in the 1850s. Voigtlander is the godfather and Lerebours is probably the uncle of Petzval lenses. Tuant, with all due respect, I would read up a bit more.

Dan

[Amedeus]

I have a 6D and a 3D ... These are petzvals ... Air spaced rear elements and an achromatic in front.

All these years I assumed the "D" series was a Petzval, but given I have never owned one, and Dallmeyer's advertising mentions it as "free from distortion," I am now not sure. Is it an RR type ? Can someone please confirm.

Thank you
Dan

[tuant]

Sorry, Dan, I know he didn't make a successful one because his was slow and not very sharp, but because of that, people started looking for ways to improve on his design and eventually Petzval came up with his design. I feel we need to give Chevalier a lot of credit for the lenses after his design. You must have done a lot of research when writing up that 29 page article on Petzval. Please share that with us when published. I have been reading Corrado's lately. I could find quite a few places for disagreement simply based on the samples in my collection. There are so many exceptions when it comes to old brass--Dozens of lens makers spanning over decades with some trying inventions and many more trying copying and modifications. You need no less than an encyclopedia just for that.

Chevalier the godfather of Petzvals ? Not even close. First, he mistakenly thought Petzval copied his design (not true). Second, he tried to suggest his L'Objectif Double ou à Verres Combinés was superior for portraits to Petzvals design (not true). Chevalier reluctantly made Petzvals in the 1850s. Voigtlander is the godfather and Lerebours is probably the uncle of Petzval lenses. Tuant, with all due respect, I would read up a bit more.

Dan

[tuant]

This post is becoming very interesting. Just for the sake of argument with no feelings hurt of course, I am curious to see if and if so, how many people would like to offer their opinion on this. We all know the argument from both by now, let's skip the ifs and buts, if you have to choose between a simple yeah and nay to the question: "Do you consider Dallmeyer 6D a Petzval lens?", what is your answer?

Mine is still Nay.

[CCHarrison]

At this point, I am with Garrett.... "ah...skip it."

[jodyake]

from my reading and research the Petzval lens had a few modifications over the years. I have some voightlanders, a scovil and a 5D. they are all petzvals. Slight variations between all of them but they are still all petzvals.