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About a Dallmeyer '3D' patent Portrait lens.


rodeo_joe1

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I rediscovered the above lens during a recent clear out - to be honest I don't even remember when or how I acquired it.

 

I did some research and realised it should have a soft-focus adjustment on the rear element, which to my dismay was seized solid.

 

After applying a few drops of penetrating oil and letting it soak in, I was then faced with applying some 'brute force and ignorance' to the stubborn adjustment ring. The 'ignorance' part was that I had no idea whether it was a right or left-hand thread.

 

Logic would dictate a LH thread to avoid unscrewing the complete rear assembly, but clockwise force just wouldn't budge the thing.

 

Long story short. I eventually managed to shift it, and it's a conventional RH thread.

 

It's now cleaned, re-lubricated and turns smoothly.

 

So if you ever come across one of these rarities with a stuck rear ring. Now you know!

 

FWIW, as far as I can tell the serial number dates it back to 1878 or 1879. Only 2 years after Dallmeyer's patent application. Making it a very early example of the 3D Patent Portrait. Glass is clean too. Now all I need to do is find a mounting or retaining ring to try it out.

Edited by rodeo_joe|1
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How large a negative will the image circle cover?

At least 10"x8". Some say 10"x12", but it's a modified Petzval design, so the edges and corners are going to be fuzzy anyway.

 

The patent application and optical design can be found here. Part of the patent applies to the ability to alter the separation between the rear elements, introducing (more) spherical aberration and thus softening the overall image. It was that mechanism - a simple screw thread - that was seized on my lens.

I don't see any "lens above" at all, but I'd like to. :)

 

I've been looking for something of this sort for a long time, but with no success.

I'll post a picture or two of the lens when I've cleaned it up a bit. There's patina, and then there's a century-and-a-half of accumulated handling gunk! I want to keep it looking its age, but not filthy and uncared for.

 

There was one up for sale when I Googled it a few days ago, but I don't think you'd like the asking price.

 

I'll be moving mine on when I've had a bit of a play with it.

Edited by rodeo_joe|1
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As promised here are some pictures of the lens after its clean up. Dallmeyer_3D_top.thumb.jpg.6bcdb3ad79b43fe9325ce166c6690a3a.jpg

Dallmeyer_3D_Back.thumb.jpg.e90c2de58aad83df21d80344fc365f08.jpg

Dallmeyer_3D_Front.thumb.jpg.b5ade5540fc50385943c7e551a4cd8ff.jpg

Pity that the brass has lost a lot of varnish and become coppered.

 

Here are two close ups of the soft-focus 'mechanism' - basically the rear element is just partly unscrewed by one turn.

Dallmeyer_3D_Sharp.thumb.jpg.2e608d34286b80e6e842e8efc64267c6.jpg

P. S. I just came across Dallmeyer's spec sheet for the Patent Portrait series. The 3D version is only supposed to cover Whole-plate wide open, and 10"x8" with an f/11 stop fitted. Contrary to what's posted elsewhere online.

Dallmeyer_3D_Soft.thumb.jpg.2477fd658d1339e5d67731885406d1a4.jpg

Edited by rodeo_joe|1
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