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

[CCHarrison]

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]

Hi Dan,

It is not a real Petzval as the back flint is not flat like a Petzval. But it is not really an RR either. It resembles the Dallmeyer A type in that it has 4 turning marks to adjust softness. Even without doing any adjustment, it is much softer than a regular RR. You could get a pretty swirling picture with a D for portrait. It is more like a Portrait Euryscop, something in between a Petzval and and RR, very useful and fun to use.

Tuant

[CCHarrison]

Hi Tuant,

Not sure I fully understand... Is there an air space between the rear elements? See the attached image which shows the differences b/t the Dallmeyer PP lens (TOP) and the original Petzval design (BOTTOM)

Thanks !
Dan

[goamules]

It's a petzval. The rear glass is air spaced, and reversed order like all patent Dallmeyers, shown in your diagram. Also, the front is a thick cemented achromat, not a thin one like RRs.

[tuant]

Yes, Garrett is right in that there is always air-space between the rear elements, but unlike Petzval, its rear flint is convex instead of being flat. The design is very different from a Petzval. It is more like an RR but with a spaced rear instead. I am not sure if we can call these lenses Petzval, although I would love to so I can cash in on my D and A type for a lot more on Ebay in the future

Hi Tuant,

Not sure I fully understand... Is there an air space between the rear elements? See the attached image which shows the differences b/t the Dallmeyer PP lens (TOP) and the original Petzval design (BOTTOM)

Thanks !
Dan

[CCHarrison]

Tuant,

The Dallmeyer PP design is considered a Petzval - even if with its differing curves. The flatness of the rear flint doesnt define a Petzval.

Dan

[tuant]

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

Tuant,

The Dallmeyer PP design is considered a Petzval - even if with its differing curves. The flatness of the rear flint doesnt define a Petzval.

Dan

[Steven Tribe]

I think Dan has a valid point.
There is no doubt that the first (Portrait and Group F6) from around 1866 (the first design with the famous set of 4 rear marks) was a modified Petzval.
But when Lens VM talks about the later D3 - D8 he says "Portrait RR?" and that the glass may come from central Europe (trace radioactivity). But how a distance control of softness could be achieved, I have no idea!

[tuant]

I hope Eddie doesn't see this post If he starts selling me a 6D as a Petzval, I will sue his ass off! And if he refuses a refund and a sincere apology, I will drive all the way to Kingston to set his garage on fire! Poor Eddie Sorry, A Dallmeyer D 6 is not a Petzval for me, nor will it ever be. We should call it Nontraditional or Modified Petzval if we have to just to avoid confusion. It may be better if we don't ever mention the magic word when we talk about such lenses.

Tuant

[alex from holland]

To be honest I don't see much difference between a D and a A. As the d is a bit slower it has a bit more DOF.
They both swirl, have the sweet spot in the centre and fade towards the outside