What is a A. J. Thompson & Co Petzval lens about?

[SteveKarr]

Hi Eveyone,
I have a lens & camera that is part of a Learning Channel program I am working on about Wet Plate & the cameras they (we) use.

So the producer sends me an 8x10 camera (he got at auction)
that needs some love in terms of wood work & bellows. So I'm looking for anything you guys and gals may know about restoration of this period stuff.

But the big question I have in about the lens:

A.J. Thompson & Co : Importers : Boston

It seems like a 10" Magic Lantern lens because it is without a slot for stops. It has a 10" distance from the rear element to the paper when focused at infinity and a 76 mm rear element diameter, and is 150mm from front lens to back lens. Is this how you can somehow find the speed? And the flange as "France" stamped on it.

I have removed the 2 cells but have not been able to get the glass out of the brass to clean it. Any ideas??

Any info, stories & lore would be great.

I'd also like to get a ballpark value for a lens like this. The glass is a bit dirty but seem like a cleaning would clear that all up. The brass is ok and the flange is with it.

Thanks for reading this far!

Steve

PS Jim & Eddie HELP !!!!! hahahahaha

[Mark Sawyer]

Such a coincidence! Today and last weekend, I was working with an A.T. (not A. J.) Thompson lens on some half-plate wet plates! I was using my smaller one, about an 8" f/4.6 that's 110mm long overall (90mm lens-to-lens) with a 160mm back focus, but I also have a larger approximate 10" f/5 A.T. Thompson that's 160mm long overall (115mm lens-to-lens) with a 180mm back focus. They look very much like yours, but a little smaller.

These are indeed magic lantern lenses, and I think they're quite nice little Petzvals. Garrett ("goamules" on this forum) was over today, and thinks these are Darlots by some of the hardware on them, and I tend to agree. The Vademecum doesn't mention them.

The distance from the back element to the plate is the "back focus", not the focal length, which is about from the plane of the f/stop (if it had one) to the film. I'd guess it would be maybe 1/2 an inch behind the focusing wheel's axle, but it's hard to say, as it was moved around on different lenses to flatten the field and reduce pin-cushion and barrel distortion.

To find your f/stop, measure the lens' inner diameter through the front element, and divide the focal length (not the back focus) by that inner diameter.
They aren't particularly rare or distinguished, (although I like mine!), and should only be worth $100 - $200 in the condition yours is in, but these are the days of Petzval-Madness, so that could easily be tripled on the right day.

Some images from my little one:

[goamules]

Like Mark said. But also a clue to it being a magic lantern is that the lettering is written so that it can be read when the focus knob is on top. This is how they are typically positioned, it's easier to grab on top. Why did the focus knob on camera lenses move to the bottom (though the very early ones were on top sometimes too)? Because waterhouse slots came along and you couldn't have the stops falling out....so the knobs were moved to the bottom. But Magic Lantern lenses didn't need to change. The lettering isn't always this way, but often is.

[Jody_S]

Garrett ("goamules" on this forum) was over today, and thinks these are Darlots by some of the hardware on them, and I tend to agree.

I've seen many of these come and go. I do believe it probably is made by Darlot. A T Thompson was only one of many mfrs for the magic lanterns and some of the others actually say Darlot on the lens. Family resemblance is identical. (...) Usually if you look real close on the focus knob you can find a tiny Made in France.

From: Looking for info on petzval lens


So on the strength of these threads, I recently purchased 2 rather large (approx. 18" f6) A.T. Thomson & Co petzvals from the famous auction site. They came in yesterday and I started taking them apart to clean. Externally, the only indication was a "France" on one of the flanges. This would indicate a date after 1902 (?) since that is when country of origin labeling was mandated, however it seems some European countries started earlier than this and it says simply "France" rather than "Made in France" as would be required by Country of Origin laws.

Against the Darlot hypothesis was the fact that Benjamin French & Co was the sole agent for Darlot for North America, however B.F. & Co went out of business in 1890 and my lenses may have been made after that. Also, there's no reason to assume that A.T. Thomson sourced all of their lenses from the same supplier for their entire production. Also they may well have purchased these locally from B.F. & Co., which might not have stamped them as they normally did, since Thomson did their own engraving.

Upon opening the first lens, I found rice writing on both the front and the larger of the 2 rear elements:

Front


Rear


So my question: has anyone ever seen a Darlot lens marked this way? Because to me, this would more likely indicate Gasc & Charconnet or some other French manufacturer.

[Jody_S]

Maybe I should show off the lenses to get people interested?



The focusing knob, and especially the 4 screws that attach it, are 100% Darlot. The rounded heads are quite distinctive. I no longer own any Gasc & Charconnet, but there is a large and stupidly overpriced polished one on fleabay right now that shows their screws are quite different (flush, with tapered recessed heads).

[Jody_S]

The Gasc & Charconnet lens from eBay, crop of their photo:

[Steven Tribe]

I’ll some ideas I will check out tomorrow.

But as a starter, I don’t believe that Darlot - at least by the 1890’s - actually Manufactured their own brasswork.

The tall 4 iron screws on the “gear box” and the wide double rilled turning wheel look familiar!

[cuypers1807]

I have one just like that. Mine is 300mm f/4 and covers 8x10 at infinity.
I was able to take mine apart and the glass had no markings on the edge. It unfortunately didn't have a flange so I sent it to SK Grimes to have one made.

[Jody_S]

But as a starter, I don’t believe that Darlot - at least by the 1890’s - actually Manufactured their own brasswork.

If the French lens-making industry was anything like the British camera-making industry, there were specialty shops that sold standard barrels and fittings, which would explain why so many of my lenses of different manufacturers fit the same flanges (from that period anyway).

[Jody_S]

I have one just like that. Mine is 300mm f/4 and covers 8x10 at infinity.
I was able to take mine apart and the glass had no markings on the edge. It unfortunately didn't have a flange so I sent it to SK Grimes to have one made.

I was lucky enough to get 1 flange with the pair, I'm going to copy it as best I can on my lathe in the spring (unheated garage). Honestly I think I would have preferred 300mm f4 than 18"/f6, though I don't know if there will be much difference in practice with the image, the dof might be similar. Yes I know there are formulae that would give me the answer with 14 significant digits. The seller didn't give much info, just overall dimensions, so I paid my money and took a gamble.

I certainly don't need the extra speed, it's hard enough to shoot an f6 lens with no shutter nor aperture on X-ray film. I might have a Packard somewhere that covers this, but that creates problems for mounting also, since it's too heavy to hang completely off the front of any of my 8x10s, and my Packard will only cover the barrel, not the hood so I can't front-mount it either. I might end up shooting paper.