A different version of the Darlot Petzval - or a standard "add-on"?

[Steven Tribe]

This is a large 1864/1865 Jamin Darlot which I had decided to prepare for possible sale. You can have too many Portrait lenses!

This is not a lens I had taken much notice of when I bought it as part of a job lot. It has been lent out for a couple of years to a more active portrait photographer. It's only claim to fame has been the unique brass flange and a very extensive edge lens text with named people in addition to "A. Darlot a Paris"

However, taking it apart to-day, to photograph the text, I discovered that lens barrel can be screwed apart near the front lens. This gives a extension piece of 1.5cm width.
Without the extension tube fitted, the Waterhouse slot is exactly midway in the barrel.

There are a number of explanations for this that I can think of:

1. The lens was sold with 2 front achromats for different focal lengths and the distance piece is used with one of these (unlikely!).

2. Darlot used a extended barrel to introduce "flou" in the Universal lens he introduced at the same time. So a soft lens add-on?

3. It is for sole use when the front cell is used at the rear for a landscape lens. That is, it extend the distance from the aperture control to the achromat. Or lengthens the lens hood effect of the front part of the barrel?

Anyone have any opinions about these or other ideas? There are markings to the thread that indicate it is supplied by Darlot. It could be an item that was a option.
The original lens hood has gone, which is pretty common in Petzvals with the landscape alternative.

[Steven Tribe]

While I had the lens split up, I decided to see if the extra text on the achromat would give any response through Google.
For once, the text was absolutely clear. It reads:

A. Chouffet a Montecheroux Doubs.

Montecheroux is small town (pop.about 500) in region of Doubs in the extreme east of France.

There are still people with this surname living in the town. There was an Armand Chouffet who was a Socialist politician, but Photography was not listed as a Hobby!
This the second time I have found names of users/repairers on Petzval achromats!

[Mark Sawyer]

An interesting variation with a touch of mystery! I doubt this was for soft focus purposes; the first experiments with that (that I know of) would be the 1867 Dallmeyer Patent Portrait lenses.

Jamin-Darlot's larger Cone Centralisateurs had variable spacing for achieving optimum aberration balance, (mostly the field curvature, I suspect). Maybe it's a variation on that, but I doubt it...

Maybe this was part of a casket set? Maybe a way to shorten the barrel to prevent vignetting when used in landscape configuration?

The mystery goes on...

[Steven Tribe]

I think Francophiles would suggest that the Darlot Universal Petzval "flou" beats the Dallmeyer Patent by about a year!

When I can find time, I'll have a go at documenting the "flou" effect as I have the Universal casket set.

I wasn't aware that the bigger cones had something similar - perhaps even back to the Jamin period. Dallmeyer was unlucky with the RR Patent as well, although he and Steinheil reached an agreement!

[franzcalab]

There was another Armand Chouffet, born in 1903. He was a pilote and a photographer specialized in aerial photography. Unfortunately few information on the web.
I found only this page:
http://www.leuropevueduciel.com/musee-photo-aerienne-armand-chouffet.php

P.S.: I follow this forum for some time but is my first message... Hello Folks!!!

[Steven Tribe]

Thanks Franz!

Whoever A. Chouffet was, he had a very good teacher in writing with pen and ink! By far the best writing I have seen. And he made a decent job of recementing the achromat too!

[Mark Sawyer]

I think Francophiles would suggest that the Darlot Universal Petzval "flou" beats the Dallmeyer Patent by about a year!

When I can find time, I'll have a go at documenting the "flou" effect as I have the Universal casket set.

I wasn't aware that the bigger cones had something similar - perhaps even back to the Jamin period. Dallmeyer was unlucky with the RR Patent as well, although he and Steinheil reached an agreement!

Here's a quote from an Eastman House publication on the Cone Centralisateur (online at http://image.eastmanhouse.org/files/GEH_1962_11_05.pdf )

"Although basically nothing but a Petzval objective, this lens embodied several interesting features, the most distinguishing characteristic being the conical shape of the rear half of the lens barrel (cone centralisateur) which was intended to prevent internally reflected light from reaching the photographic plate. Also the separation between the front and rear components could be varied, either by simply drawing out the front portion of the barrel or by use of a rack and pinion mechanism, the purpose of this being to enable the user to obtain the best possible aberration correction for any particular object distance."

Do you know if Jamin-Darlot were using "flou" effect as a deliberate aesthetic choice? My understanding is that soft focus as an end in itself wasn't done until the 1880's. (Dallmeyer's "soft focus" was about depth of field, not a softened image.) Certainly the landscape lenses were soft focus when used wide open, but that's why early users kept them well stopped down...

[Amedeus]

Another option ... not enough long barrels in stock to deliver the correct length, so add a spacer to get there ... pragmatism ... lol

Not as "flou" but still flou

[Steven Tribe]

I think I may solved the question of what Darlot intended with this particular construction.

D'Agostini's book has a final section, written by U.Menichini, with further examples of Convertible lenses.

Under the Darlot section (pages 350 - 356) there is a discussion of a second variant which has a great deal in common with mine. This is a combination of a Portrait lens and a Landscape lens. The main part of the barrel has the Waterhouse stop in exact central position - like mine. There is a small extension, which Menichini suggests is added to the rear just converts to a "normal" Petzval- that is, the ratio between from lenses and the WHS distances. He measures the data for the short Petzval as efl 18.73cm and F.2.9 and the long (normal) Petzval efl 19.57cm and F3.05. Mine measures up the same - or very close to this. He argues that these two (very slightly!) different represent a real choice for the portrait photographer. I don't think this is very likely. I think it is a question placing the aperture at the best position from the landscape lens.

There can be little doubt that the short section was intended to be placed at the rear as it was painted black like the Cone Centalisateur. Perhaps mine lost its paint like quite a lot of Cones have due to misguided owners.

[alex from holland]

Mark,

Do you have a picture of that adjustable spacing.
I have several cones, but none of them have this.
Or do you mean the possibility to pull out the landscape (front) part?

Alex


An interesting variation with a touch of mystery! I doubt this was for soft focus purposes; the first experiments with that (that I know of) would be the 1867 Dallmeyer Patent Portrait lenses.

Jamin-Darlot's larger Cone Centralisateurs had variable spacing for achieving optimum aberration balance, (mostly the field curvature, I suspect). Maybe it's a variation on that, but I doubt it...

Maybe this was part of a casket set? Maybe a way to shorten the barrel to prevent vignetting when used in landscape configuration?

The mystery goes on...