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View Full Version : Looking for info on petzval lens



Jim Cole
27-Mar-2009, 11:14
I just acquired this new petzval lens and its markings show A.T. Thompson & Co Importers. Focal length looks to be about 6 1/4 inches (although I'm a little unsure how to measure it with the focus capability). The seller said that it may have been produced by Darlot, Paris for Thompson. I'm looking for a little historical perspective. The lens is about 5" tall and about 2 7/8 " across the lens shade.

Information is pretty sparse.

Anyone have any info they would like to share to help place the lens in time and place?

http://farm4.static.flickr.com/3619/3390479952_ef0784b59c_o.jpg

http://farm4.static.flickr.com/3553/3390479854_a47c71256b_o.jpg

Thanks,
Jim

Carioca
27-Mar-2009, 11:24
If possible, you could try to carefully disassemble the rear glass elements from their housing. Some manufacturers wrote their brand and/or name on the side (rim) of the glass with a pencil.

Jim Cole
27-Mar-2009, 13:07
If possible, you could try to carefully disassemble the rear glass elements from their housing. Some manufacturers wrote their brand and/or name on the side (rim) of the glass with a pencil.

Thanks for that tip. I'll check it out if I don't get any other info.

CCHarrison
27-Mar-2009, 15:59
Its most certainly a magic lantern lens. A.T. Thompson & Co was known for their magic lanterns - and I dont believe they marketed camera lenses. Having said that it could be a Darlot made lens since they made both camera and lantern lenses...

Dan

Jim Cole
27-Mar-2009, 16:27
Dan,

Thanks for that piece of info. It does have only one focus knob like the Magic Lanterns. It would seem a camera lens would have dual knobs.

I'll keep fishing.

Thanks

Jim Cole
27-Mar-2009, 16:28
If possible, you could try to carefully disassemble the rear glass elements from their housing. Some manufacturers wrote their brand and/or name on the side (rim) of the glass with a pencil.

I tried disassembling the lens cells to check for pencil marks as suggested by Carioca. Alas, I couldn't get the front cell apart (I wanted to look anyway), and the only marking on the rear cell elements was a penciled number "12" on the edge of the thicker of the two elements. No sign of a manufacturer.

Thanks

Gene McCluney
27-Mar-2009, 16:55
Dan,

Thanks for that piece of info. It does have only one focus knob like the Magic Lanterns. It would seem a camera lens would have dual knobs.

I'll keep fishing.

Thanks

You are incorrect, camera lenses of this period also have just one focusing knob. But..camera lenses have provision for waterhouse stops, and your lens does not, which is a sure giveaway for it being a Magic Lantern lens. Now magic lantern lenses and camera lenses are the same in optical construction if a Petsval design, except for the slot for waterhouse stops.

a 12" lens is about right for a focal length for a magic lantern, as the magic lantern slides which are approx. 3x4" would just use the central "sharp" area of a 12" Petsval.

Jim Cole
27-Mar-2009, 17:08
You are incorrect, camera lenses of this period also have just one focusing knob. But..camera lenses have provision for waterhouse stops, and your lens does not, which is a sure giveaway for it being a Magic Lantern lens. Now magic lantern lenses and camera lenses are the same in optical construction if a Petsval design, except for the slot for waterhouse stops.

a 12" lens is about right for a focal length for a magic lantern, as the magic lantern slides which are approx. 3x4" would just use the central "sharp" area of a 12" Petsval.

Gene,

Thanks for the correction. Being new to these old lenses I did not know that the waterhouse stop slot marked the difference. I wasn't sure if it was a developmental time line or a camera/lantern difference that designated the waterhouse stops.

Focal length is about half of the suggested 12". If I project a sharp image on a piece of mat board, the focal length is about 6 1/2" as measured from the center of the lens, which is where I assume I should start the measurement with a dual group lens. I haven't had a chance to make a lens board yet to put this on my 4x5.

Thanks again

Jim Galli
27-Mar-2009, 20:51
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. It really doesn't matter much in any case. If you like the signature that a Petzval lens gives it matters little whose name is on it. Usually if you look real close on the focus knob you can find a tiny Made in France. Typically there are lots of 6" and a few less 8" that share that body. There were 10" ones but they are a magnitude larger. You should have some fun with it on a 4X5.

Jim Cole
27-Mar-2009, 22:03
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. It really doesn't matter much in any case. If you like the signature that a Petzval lens gives it matters little whose name is on it. Usually if you look real close on the focus knob you can find a tiny Made in France. Typically there are lots of 6" and a few less 8" that share that body. There were 10" ones but they are a magnitude larger.

Jim, Thanks for the additional info.


You should have some fun with it on a 4X5.

Looking forward to it. Your work has inspired me.

Thanks,
Jim

goamules
28-Mar-2009, 08:13
<quote>If possible, you could try to carefully disassemble the rear glass elements...</quote>

Bear in mind that often the front element is the one with the signature. I have several Darlots with just the cemented front marked. Enjoy the lens.

Jim Cole
28-Mar-2009, 08:42
Bear in mind that often the front element is the one with the signature. I have several Darlots with just the cemented front marked. Enjoy the lens.

I'd like to take a look at the front elements, but don't know how to remove the retaining ring in the cell. It does not extend past the housing like the rear cell and I can't figure out how to torque it loose without risking the glass. Any suggestions?

Thanks

Jim Cole
5-Apr-2009, 18:19
Just started experimenting with this lens today and I do not seem to be able to get the signature swirlies from it.

I checked to make sure the elements are arranged as per the beginning of this essay:

http://www.antiquecameras.net/petzvallens.html

and also checked to make sure the image circle is not so large as to make the swirlies outside the image area on my 4x5. Seems to have about a 6" image circle which I can easily reach the end of with rise on my Ebony RW45.

Any ideas???

Thanks

goamules
5-Apr-2009, 19:54
Well, don't forget the swirl was an abberation, and it's not "easy" to get the effect. You need scattered light and dark patterns to see it best. Try this: position the camera in front of foliage at, say, 8 feet. Focus on the leaves, then slowly focus further out (as if there was a model or subject between you and the leaves) and see if you get the effect. If not there, move the camera back to 20 or so feet and try again. Etc....

Also, I didn't see what you calculated the speed to be, but the slower petzvals have a less curved field and are less likely to have swirl. I have a f6 Dallmeyer that doesn't do it, but the f3.8 does.

Jim Cole
5-Apr-2009, 20:05
Also, I didn't see what you calculated the speed to be, but the slower petzvals have a less curved field and are less likely to have swirl. I have a f6 Dallmeyer that doesn't do it, but the f3.8 does.

I assumed the aperture to be somewhere around f4 and my first studio exposure came out pretty darn close, so it could be a standard f3.7.

Thanks for the tips. I'll give it a try outside tomorrow and see what it looks like.

It was also the first time I tried the Galli special shutter technique with two pieces of black mat board held in the hand. Calculated shutter speed was 1/8 and I was amazed that I nailed it on first try. Who needs a shutter?

Carioca
7-Apr-2009, 12:02
It's mainly a matter of camera to subject focus distance as well as the following out of focus distance to the background.

If you manage to disassemble the rear part, you can try to inverse the rearest lens element (the one facing the film). This will accentuate the swirl effect with some Petzval lenses.
Don't give up!

Sidney

Jim Cole
7-Apr-2009, 13:49
Thanks, Sidney. Took it outside yesterday and at the extremes, only seem to get large, rather obvious, circular out OOF areas, like smal individual blurred drops of water, but no swirlies.

Could be the rear element. I notice in the diagrams for Petzvals that the rear doublet has an air space between the two elements. Mine fit together conave to convex and unless the air space is only towards the center of the doublet where I cannot see, the lenses appear to be in complete contact. There is no spacer. Is there supposed to be?

The current configuration where the lenses are nestled convex to concave places an almost flat lens surface (of the thinner element) towards the front of the lens. If I reverse the thin element, it provides a definite air space between the two lenses and a much more convex surface to the front of the lens. I guess I just need to go outside and see if this configuration changes the optical performance.

EDIT & UPDATE: Figured it out. The elements in the rear doublet were fit together properly, but the doublet itself was reversed. The swirlies have revealed themselves!

Thanks to everyone for their help.

Jim

eddie
7-Apr-2009, 14:44
EDIT & UPDATE: Figured it out. The elements in the rear doublet were fit together properly, but the doublet itself was reversed. The swirlies have revealed themselves!

Thanks to everyone for their help.

Jim

also note that the dallmeyer petzvals and the voigtlander petzvals have a different rear element configuration. so you may not have has them in backwards......i bet you do now though. remember back in the day they did not want swirls.....this is a new "art". after you finish playing with it you may try switching them back and reexamining the photos. you may have some nice shots even though you get no swirls.

have fun.

eddie

Carioca
7-Apr-2009, 15:08
I'm happy for you!
Don't get too dizzy! ;)

S.

Jim Cole
7-Apr-2009, 15:28
also note that the dallmeyer petzvals and the voigtlander petzvals have a different rear element configuration. so you may not have has them in backwards......i bet you do now though. remember back in the day they did not want swirls.....this is a new "art". after you finish playing with it you may try switching them back and reexamining the photos. you may have some nice shots even though you get no swirls.

have fun.

eddie

Eddie,

Thanks for the tip. Actually, it looks like the original Petzval configuration now. I may have reversed the doublet when I was looking for some identifying marks on the elements. Either way, I will make some shots both ways and see what kind of interesting things happen. I'm looking forward to it. It's nice to know that I can turn the effect on or off depending on the subject.

Jim