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psychoanalyst
25-Jul-2011, 14:12
Hello,

A friend of mine recently acquired a Benjamin French lens and from what I read, I believe its a Darlot.

The lens construction, according to what he told me, consists of 2 separate elements in the back and a single element in the front.

Are such designs common? Especially for Darlots? I initially assumed that it must be a Petzval, but a single element in front changes that.

In any case, would the above Darlot swirl like conventional Petzvals do under the right conditions?

Thanks.

Avi

davehyams
25-Jul-2011, 14:18
Its most likely a Petzval, a cemented doublet up front and an air spaced doublet in the rear. I had a Benjamin French Darlot, and it swirled a when coaxed, but its not the over whelming swirl some of the faster lenses out there have. Great lenses in my experience. What focal length is it?? Is it cut for stops?

psychoanalyst
25-Jul-2011, 14:23
Dave,

Thanks! I hope its a Petzval since I want to loan it from my friend!:)

It is apparently a 5". I will check with him about the stops, but I believe he mentioned that it had a slot for waterhouse stops, but the stops themselves were not provided.

The target format is a Speed Graphic 4x5. I wonder how much it would swirl on that?

Avi

goamules
25-Jul-2011, 14:46
... according to what he told me, consists of 2 separate elements in the back and a single element in the front.

Are such designs common? Especially for Darlots? I initially assumed that it must be a Petzval, but a single element in front changes that...

What he thinks is a single piece of glass is almost certainly a cemented double. It's a petzval, and may have that swirl you need, the only way to tell is to try it. The faster lenses, F4 or so, do it more.

CCHarrison
25-Jul-2011, 15:37
If you go to my site, you will find an 1890 Benj French Catalgoue carrying all the Darlot lenses at the time....

http://antiquecameras.net/1890lenscatalogue.html


Dan

psychoanalyst
26-Jul-2011, 05:01
What he thinks is a single piece of glass is almost certainly a cemented double. It's a petzval, and may have that swirl you need, the only way to tell is to try it. The faster lenses, F4 or so, do it more.

You are spot on. My friend confirmed that the front is indeed a doublet. I am now in the process of acquiring the lens from him!:)

Thanks.

Avi

psychoanalyst
26-Jul-2011, 05:04
If you go to my site, you will find an 1890 Benj French Catalgoue carrying all the Darlot lenses at the time....

http://antiquecameras.net/1890lenscatalogue.html


Dan

Dan,

Thanks. I have checked your site and according to that there does not seem to be a 5" portrait lens with rack and pinion. Its either 41/2" or 51/2".....so I am guessing my friend got the focal length wrong.

Anyways, I will know soon enough.

Its an amazing website you have there. I hope to setup something very similar for my beloved Kilfitt lenses.

Avi

psychoanalyst
28-Jul-2011, 09:56
I got the lens today. Am a bit confused.

The lens has only one engraving on the brass body that reads :

Benj French & Co
Boston

I have not opened up the elements yet to confirm its Petzval design. I will go home and upload detailed pictures.

But I was expecting either a B.F. and Co. or a Darlot engraving somewhere..

Avi

goamules
28-Jul-2011, 11:35
Now I'm confused! You say it's engraved, but that you were expecting it to be engraved? Sometimes these import lenses weren't marked by the maker, sometimes they didn't have any mark, and the BF company had several different engravings.

As far as the order of the rear element, make sure the most curved surfaces of the two lenses are nested together, with the metal ring between. The thin lens faces the film. On the front, the curved part faces outwards, towards the sitter.

psychoanalyst
28-Jul-2011, 12:22
Garrett,

That is a relief. Well..I was expecting an engraving of some sort...no reason. I was under the impression that all Darlot imports had the engravings B.F. and Co.

According to Dan's website: http://antiquecameras.net/1890lenscatalogue.html

it should say that.

But mine says Benj. French and Co. and what is interesting is the footnote on the above website (in the Darlot section) also reads Benj. French and Co.

Hence the confusion.

I will take pictures and share with all of you soon.

Avi

psychoanalyst
28-Jul-2011, 14:06
Below are pictures of the lens itself. Maybe this might both clear my confusions as well add to the knowledge base on Benjamin French lenses?

I believe it has all the signatures (minus actual picture) of a Petzval construction. Though I need to verify the front cell. It comes with a mounting flange and it should be easy to mount onto my Speed Graphic board by drilling holes into it and using screws.

Thanks.

Avi

http://farm7.static.flickr.com/6136/5985846440_3eb1b17ec4_m.jpg (http://www.flickr.com/photos/smiling_buddha/5985846440/)

SUPPOSEDLY A 5" PETZVAL. SHOT AGAINST A BOX OF MY 120 FILM TO GIVE YOU AN IDEA OF THE SIZE..

http://farm7.static.flickr.com/6135/5985283283_ce18742b73_m.jpg (http://www.flickr.com/photos/smiling_buddha/5985283283/)

http://farm7.static.flickr.com/6124/5985846116_a903986678_m.jpg (http://www.flickr.com/photos/smiling_buddha/5985846116/)

THE ITEM ON THE LEFT FORMS THE GROUP OF REAR ELEMENTS. AS SEEN BELOW, THE TWO ELEMENTS ARE SEPARATED BY A THIN RING.

http://farm7.static.flickr.com/6007/5985284099_7b10a5f3fc_m.jpg (http://www.flickr.com/photos/smiling_buddha/5985284099/)

THE REAR ELEMENT MEASURES ROUGHLY 1.5" IN DIAMETER, MAKING IT A ROUGHLY F3.3 LENS? THE FRONT I GUESS HAS TO BE A CEMENTED DOUBLET, BUT WITH IT IN THE HOUSING I CANNOT REALLY TELL.

Steven Tribe
28-Jul-2011, 15:23
Attractive lens! Given the dimensions you have mentioned, if your Speed Graphic is 4x5", I think you will have dark corners.

psychoanalyst
28-Jul-2011, 19:54
Attractive lens! Given the dimensions you have mentioned, if your Speed Graphic is 4x5", I think you will have dark corners.

Steven,

Yes...my Speed is a 4x5. But if I get dark corners it would be ok, because I am looking for the swirlies and I can crop off the dark edges after scanning.

Am I making sense here?

Avi

psychoanalyst
28-Jul-2011, 19:57
Can anyone confirm that this is a Darlot Petzval?

Thanks.

Avi

Steven Tribe
29-Jul-2011, 03:25
I don't recall seeing a Darlot where the front achromat couldn't be unscrewed from the inside? I would guess this is an early B.French import when he still bothered to have the more complete engraving. If you can remove the front achromat from the front cell, it may have text on the ground edges.
If it isn't a Darlot, it really doesn't matter. Darlot was the most organised and biggest french maker - but everyone else supplying to B.F & Co. was just as a competent a Petzval maker.

psychoanalyst
29-Jul-2011, 04:54
Steven,

I confirmed. Can't figure how to remove the front doublet from its housing. But given the thickness of the whole thing.

Lets see if someone knows a bit more about this guy. The mystery of the B.F. Darlot!

Btw....any advice on how I could clean the elements? I am going to shoot before I decide it needs cleaning or not, but I wanted to know anyway.

Thanks a lot.

Avi

goamules
29-Jul-2011, 06:28
It looks like a nice petzval of unknown manufacturer. Like Steven says, sometimes you cannot tell who made them. I see things in the knob and front element that look Darlot, but the back element doesn't. Who knows, but I'm sure it will take good pictures. The very small and the very large Petzvals are the hardest to find. It's missing it's hood/sunshade.

You can clean the glass with soapy water. Just don't drop it!

psychoanalyst
29-Jul-2011, 06:58
It looks like a nice petzval of unknown manufacturer. Like Steven says, sometimes you cannot tell who made them. I see things in the knob and front element that look Darlot, but the back element doesn't. Who knows, but I'm sure it will take good pictures. You can clean the glass with soapy water. Just don't drop it!

Soap water and cleanroom paper it is......

I don't really care who made it as long as its a Petzval (which is does look like), but I would would be nice to get it identified and ball park dated.

How can one tell that the front is a doublet? Just curious.

Thanks a lot.

Avi

goamules
29-Jul-2011, 07:03
...I don't really care who made it as long as its a Petzval (which is does look like), but I would would be nice to get it identified and ball park dated.

How can one tell that the front is a doublet? Just curious. ...

It's a petzval. The rear air-spaced elements and the length to diameter ratio are all you need to know to confirm. The front will show a glue line on the edge, very close to one side. Or you can play with the reflections, you should see one dim one in there when you hold it under a small light. That's the harder way.

I've never seen a script Benj French engraving like this. Could be early, could be late. The company was in business a long time, so you have a wide range. I'd guess about 1875 or 80.

psychoanalyst
30-Jul-2011, 18:47
Just got done cleaning the lens. It was easy. Tried removing the all the elements from the housing to no avail. Just the one lens that was part of the air spaced doublet.

Anyways, its nice and clean and free of any dust etc.

Only thing left to do is to mount it to a Speed Graphic board. A trip to the machine shop is next on the list.

Btw....what the is the exact role of the radial drive? I can see that it changes the separation between the front and rear elements, but what effect does that have?

Thanks.

Avi