View Full Version : Unmarked Brass Portrait Lens

31-Mar-2014, 20:42
I bought this a couple of years ago on Ebay, and am now getting ready to mount it on the 8X10 Seneca. It's way too heavy and the flange is too big to mount on a lens board and hang on the front standard, so I will need to build some kind of a cradle to rest on the bed and slide the lens back into the front standard. If I install the extension rail and rack the rear standard back onto it, I should be able to focus the beast somewhat closer than infinity.

The lens is lacquered brass and completely unmarked except for the shell of a Wollensak Studio shutter No. 3, Style B. Some previous owner removed all the shutter's innards, so now it's wide open and shutterless. Checking the old Wollensak catalogs, the lens looks externally very much like a Series A (Vesta) No. 5., except the hood is longer.

But internally, I think it's different. I gather the Series A and later Vesta were Petzval types, but after taking the cells apart to clean all the surfaces, which it needed, the design seems to be different from a Petzval. I did some careful checking of reflections and curvatures, and this lens appears to be like an extra rapid rectilinear with an extra thin weakly positive meniscus element mounted next to the rear cemented doublet on the diaphragm side. This meniscus element is spun into it's own thin cell that screws into the back of the rear doublet cell, so it wasn't added as an afterthought. There is a faint hint of overall haze in the cement layers of both doublets that can be seen by shining a strong light on the doublets at a shallow angle and by looking through the doublets at a strong light source. It shouldn't be bad enough to seriously impair performance, but it does allow me to see the deeply curved cement interface in each doublet.

I drew a rough freehand sketch diagram, not to scale, but it should show the optical layout. I haven't found this in Kingslake or any other reference I can find.

Any ideas who might have made this lens or what type it might be?


Jason Greenberg Motamedi
31-Mar-2014, 20:51
The schematic looks a little like a Heliar, but it is much too long.

1-Apr-2014, 09:02
Could it be a Vitax? I know the Vitax is a modified, soft focus petzval with adjustment. Is that the extra cell? If the FL is at the short end of what you estimate, you're right around f3.8


1-Apr-2014, 09:32
I've never handled a Vitax, but they have an adjustment knob sticking out the side of the barrel. This one has no adjustment knob, no hole where one might have been, and no internal parts for an adjustment mechanism. The 'extra' cell screws into the back of the rear cell, with no markings for adjustment. I could probably get some kind of adjustment by unscrewing the extra cell part way, but I don't think it was designed to be adjustable.

Jason Greenberg Motamedi
1-Apr-2014, 09:44
The schematic looks a little like a Heliar, but it is much too long.

I reread what you described, and see that you said the middle element was positive, so I retract my statement, on a Heliar it is negative.

This is certainly not a Vitax, which is just a Dallmeyer type Petzval.

Steven Tribe
1-Apr-2014, 10:01
I would call this a Petzval - with a very complex and untraditional air-spaced pair. Perhaps an attempt to reduce the curvature of the focal plane? This was period when Voigtländer was¨"improving" the Taylor/Cooke triplet to the more complex Heliar.

1-Apr-2014, 10:27
Well then, I'd call it a Rapid Rectilinear with an additional simple miniscus added. Much closer to that.

1-Apr-2014, 14:39
Thanks for the replies. There are people here who have worked with an awful lot of old portrait lenses, so I get a sense that this one was not manufactured in large numbers or commonly encountered, if at all. On a hunch, I took it apart again and did a rough check of the focus of the two doublets, focusing an image of trees in the distance through a window onto a wall. The doublets seem to have roughly the same focal length, and to the unaided eye the element curvatures that can be seen look about the same. I don't have a spherometer to measure the curvatures so all I can do is guesstimate. The single meniscus element was removed for this test. This seems to indicate the lens system was based on an extra rapid rectilinear with a single element mounted near the rear doublet. This could have been as an aberration corrector, or possibly an aberration introducer for soft focus.

It doesn't seem to be a soft focus type lens based on the limited testing I was able to do, more like a petzval or RR, sharp near the optical axis and soft at the edges. I won't really know until I get it mounted on the camera somehow. I'm working up a theory on how it might have been made, but someone here may have a similar lens and know more about its history, so I'll hold off on speculating for now.

Here is the lens with the cells disassembled. In the front row, left to right are the rear doublet, the meniscus element that screws into it, and the front doublet. The doublets can be screwed into either the front or rear of the barrel, but the cells are shaped differently so not interchangeable.

The lens assembled

Looking at the front. The reflections from the flash make the haze look really bad.

Looking through the lens at some objects on the kitchen counter. I think I see a slight amount of overall haze, but I think it will look better on the ground glass with the lens on the camera. There were bright kitchen lights behind me and I think some of that light got into the back of the lens while I was taking the image.

1-Apr-2014, 15:11
That's a strange one. If, indeed, the rear is a doublet and an air separated additional lens. Are you sure about that? Have you taken the glass out of the brass mount? The rear one I mean. Because a lot of petzvals just use the mount for separation, no metal ring. Which this looks like.

Jason Greenberg Motamedi
1-Apr-2014, 15:29
pretty big shade too...

1-Apr-2014, 15:30
I can't easily take the rear element out of its cell. I would need to drill two small holes in the inner retaining ring and use a lens spanner to unscrew it. But with the meniscus element removed, I can faintly see the cement interface inside the doublet, it's slightly hazy. Also, with the meniscus element removed, I can see two bright reflections and one dim reflection of a small bright light bulb. The dim reflection is very small, as would be expected for a steeply curved surface. These are the same reflections I get from a single cell of one of my RRs.

And finally, the rear 'element' (without the meniscus element attached) has about the same focal length as the front doublet and the same general curvatures. If I'm not mistaken, the rear element of a petzval is an unsymmetrical double convex lens. My rear 'element' is a thick positive meniscus. The rear facing surface is pretty strongly curved, stronger than my petzval, although it is smaller. Also if I'm not mistaken the front doublet of a Petzval is plano-convex, or nearly so, and my front doublet has a meniscus shape like a RR.

The meniscus element in the rear group of a petzval is fairly strongly curved and negative. My meniscus has very slight curvatures, the curvatures are in the other direction, and the element is positive. The element is spun into its cell, so it's impossible to turn it around backwards when screwing it into the rear cell.

1-Apr-2014, 16:56
One thing I forgot to mention above, the rear 'element' of my lens has a thin ring of balsam separation plainly visible around the periphery. Here is the assembled lens from the rear:


No, it's not crud on the outside of the lens, it's real balsam separation.

1-Apr-2014, 17:14
Well that settles it, it's a cemented doublet. Thanks for all the evidence.

Jason Greenberg Motamedi
1-Apr-2014, 17:21
... Perhaps an attempt to reduce the curvature of the focal plane?...

I like Steven's idea of an element to correct field curvature, although the field flatters I have seen are after the rear element, so this might be an idiosyncratic attempt.

3-Apr-2014, 10:40
Could any of our collectors of big lenses tell me how common it is to see an unmarked portrait lens in a studio shutter?

I understand unmarked petzvals were common in the mid 19th century, but how about the early 20th?

I'm guessing someone patented this design back in the day, and quite a few patents were never actually built, but I'm not feeling too inclined to try to search all the lens patents between 1870 and about 1920 to see if this one turns up. I guess I'll try it out, and if it seems to work OK, use it. A name brand portrait lens in this size just isn't in my budget.

I'm the meantime while I'm waiting for the black paint to dry on the lens board I made last night, I'm thinking about candidates for a name for my unusual find.



Both of those sound slightly obscene somehow.

How about Bastard Portrait? :)

3-Apr-2014, 20:15
Got the lens mounted on a board and installed it on the Seneca. It fit...just barely.


Measured the focal length by focusing on some objects in the distance and measuring their separation on the GG. Then measured their separation using a standard lens of known focal length, my 12" Dagor. The portrait lens has a focal length of 14.5". Objects in the distance could be brought to fairly sharp focus using the loupe, but there was a somewhat diffuse look also. There was a lot of curvature of field, but that might not be a big issue with a portrait lens where objects at the edge of the field probably won't be in focus anyway. With the rear standard racked back onto the extension rail to focus at portrait distances, the field of view will be smaller and curvature of field probably will be less.

Then removed the meniscus element from the rear group and tried the lens again. Going with the theory this is an extra rapid rectilinear with an added element, the lens system might behave like a RR without the element. Overall image quality looked much the same as before, except the field of view was smaller, and I had to rack the rear standard almost all the way back. This was expected, because the removed element was positive. Focal length was 17.5 inches. Coverage seemed generous at 14.5 inches, so I think this lens would cover 11X14 without the extra element. Curvature of field was much less, partly because of the smaller field of view, but I think the meniscus element made the curvature worse, so I would say it is the opposite of a field flattener.

I think the extra element may have been added to make the lens faster and shorten the focal length so it would work with the average 8X10 studio camera. The extra curvature of field might not be a big problem at portrait distances, but I won't be able to tell until I can take some test shots.

The clear aperture inside the shutter is just under 3 inches, so the aperture appears to be about f5. With the extra element removed, the aperture is more like about f6.

It occurred to me that this lens may have been a prototype, and when it was assembled and tested it may not have met expectations. :(

There may be a good reason why more of them haven't been seen. :(

I won't really know until I have a chance to use it for some portraits and still lifes. But I haven't given up hope yet.

20-Apr-2014, 18:32
An auction just ended a few minutes ago for another unusual portrait lens, Ebay item number 301153039843. It was made by the Scientific Lens Company, is probably for 8X10, and looks strangely similar to my unmarked lens. The extra long lens hood looks about like mine, and the seller's description of the lens elements seems particularly interesting:

The thin flat lens is most interesting, because the single meniscus element in my lens looks like that at a casual glance. It's very thin and seems completely flat until looked at closely. For the most part it looks like a clear filter. The radii of curvature are very large and one surface is nearly plane.

If I'm not mistaken, there are no thin nearly flat elements in a Petzval or a Dallmeyer modified Petzval. The two thick elements are obviously not concave, otherwise the lens wouldn't have positive power to bring an image to a focus. If the two thick elements are actually thick meniscii, then this lens could be the same design as mine.

If it was snagged by a forum member, if you would be interested in doing an inspection of the lens elements I would be very interested in reading what you found out.

Steven Tribe
21-Apr-2014, 04:56
I think you are on the right path!

There is a previous thread from 2012 - so use search for scientific lens portrait in titles.
The information will be depressing, I'm afraid - Jim Galli had one disappear under repair!
It gives a possible explanation of why it is anonymous and the connection with the Scientific .......

21-Apr-2014, 16:26
I think you are on the right path!

There is a previous thread from 2012 - so use search for scientific lens portrait in titles.
The information will be depressing, I'm afraid - Jim Galli had one disappear under repair!
It gives a possible explanation of why it is anonymous and the connection with the Scientific .......
Thanks for the link, that was an enjoyable read. Apparently my lens was made by Nehring or his successor Koehler, and the lack of markings could be due to having been manufactured and sold under dubious circumstances. Garrett mentioned Nehring had a few patents, so this could be a starting point for looking up his patents some time in the future.

I haven't made any images with it yet, but I got it focused on some bottles set on top of an empty 55 gallon drum, and it looks like it will work OK for portraits and still lifes and such.
Fortunately I didn't pay a lot for it compared to what even a humble Wolly Vesta would sell for, so all in all not a bad deal.

Steven Tribe
22-Apr-2014, 01:28
Certainly an interesting sub-chapter in American lens manufacture! These days, it would have been a "kick start" project.

6-Jul-2015, 21:55
I have been searching for information on the Scientific Lens Company Ocular 8x10 Lens for quite awhile and thought I had seen everything.
I know of one in Tonapaugh that turned to dust and one other listed on bay not much info on the Ocular out there. I just saw this post from last year
and contacted desertrat who suggested i post to the old thread so everyone can get the info, so here goes. I am new to posting on LFPF other then
dropping in now and again to look around. I needed some advice on a whole plate camera, plate holders and a frozen lens, now I have to
contribute. I am fairly new to Large Format cameras and Lens but have been shooting film and Digital for a long time.

Follow up on Unmarked Brass Portrait Lens
My lens looks like desertrats but it is engraved.

Scientific lens Co NY

License #275 Ocular 8x10

Patent Feb 2 1904 April 12 1904 May 31 1904

when I got the lens looking thru the glass was like a looking at a snowflake or cobweb i thought this was fungus. The elements were easy to unscrew from brass barrel and take out of mounts. I soaked the two front elements in peroxide and alcohol they looked just like the doublet in the schematic but were
two lens's not cemented.The rear cells were cleaned the same way and were almost identical not cemented and there was a thin positive meniscus element
pressed in a threaded mount that screwed into to the rear doublet on the diaphragm side.

When I put the lens back together there were newton rings. I thought maybe because they were almost identical i might have mixed them up switched them around and found out that if i loosened them a little the newton rings would disappear.

After a little research I decided the front element was a cemented doublet and the snowflakes i cleaned up was Balsam now I am thinking the same in the rear unless there is a spacer missing. Another thing i noticed after taking the lens apart yesterday was that one of the doublets when nested is a perfect fit the other is not I found the photos of the Lens that was listed on Ebay and It looks like there is something missing on mine the front and rear elements are not interchangeable. I put the lens back together today put it on my camera and it focus's, looks like a Petzval Boca Monster and no Newtons rings, but I really will not know intel i shoot some film.

I was wondering about putting oil between elements, but may not have to if neg looks as good as the ground glass.

here are some photos of my lens and some info I have collected while pulling my hair out.


Process: the photomechanics of printed illustration, Volume 12
*By Henry Snowden Ward, Process Engravers' Association, Federation of Master Process Engravers
The "Ocular" Lens.

This new portrait lens, from the Scientific Lens Co. of New York, is in the hands of C. Zimmerman & Co., on this side. The novel feature of the lens is that it alters its focal length during exposure; so that you may begin the exposure with the lens focussed on the plane of the back of head, and at the finish it will be focussed on the eyes or the tip of the nose. This alteration is produced automatically, so that there is nothing to jar or shake the camera. The lens we have tested is the 10x8 inch "Ocular." Its focal length varies from 16-2 inches to 16-35 inches maximum, and it will cover a 10 x 8 plate if required, but we should prefer not to use this focal length for anything over cabinet. The lens consists of two parts, a positive which moves, and a negative lens which is fixed. The positive is somewhat similar to the Petzval lens, except that the positive lens of the back combination is a cemented combination and not a simple lens. The negative lens which projects inside the camera screws into the outer jacket and is a very weak one (of long focal length). There is a screw-clamping arrangement in the outer jacket by which the speed of the movement may be varied to suit the exposure, and arrangements are also made by a series of grooves into which a catch drops to vary the amount of movement to suit the scale on which the subject is rendered. Large heads or groups naturally require more variation than small heads. The clamp should be so arranged that the movement occupies about two thirds of the total exposure. A pneumatic release is connected by a Y piece with the shutter and bulb, so that shutter and lens are released simultaneously. The full aperture is f/S, and the lens may be used if preferred without the movement; but as no stops are supplied, and as there is no arrangement for inserting them, the depth of field will be somewhat limited.

6-Jul-2015, 22:27
in the last photo you can see the grooves, i compressed the spring in the jacket of the lens so you can see the series of grooves that was to vary the amount of movement.
I think there is a piece missing on my lens after reading the description of the unmarked lens in the thread.

Steven Tribe
6-Jul-2015, 23:56
Interesting project. Sounds like a mechanism doomed to fatal failure (like double curtained focal plane shutters!).

I have occasionally found achromats in Petzvals that have been "dry" – that is, the cloudy balsam has been disolved, but not renewed. The first achromats, pre-photography, had tiny air spaces (thin slithers of metallic tin) or oil between components.

7-Jul-2015, 09:30
I think there is a good chance those doublets were originally cemented. You get newton's rings when the fit is very close. I don't think there would be any harm in oiling them together as a test.

Amateur astronomers occasionally use oiled doublets in the larger achromat objectives, and usually use salad oil. I think castor oil might work better as is is non drying, has a very high viscosity, and its refractive index is a little closer to crown glass. the RI of salad oil is about 1.47, and castor oil is about 1.48. Crown glass is about 1.52.

I use castor oil for immersion oil with oil immersion microscope objectives and it works fine, even though a RI is a little lower than it should be. Immersion oil matches the RI of crown glass, but is much more expensive.

7-Jul-2015, 09:50
Lens is on a Camera Image on GG looks fine no Newtons Rings. I switched the doublets around and may have mated them properly. I am Waiting for film.
and will follow up.

8-Jul-2015, 14:38
After a closer look at lenses off camera I could see newtons rings, but not like before. I used Castor Oil as a test, substitute for Balsam on both front and rear Doublets. The lens seemed much brighter and easier to focus at portrait distance, sharp in the center with nice out of focus area's like a Petzval Portrait Lens. Then I took the Meniscus off the inside of the rear doublet and could focus but needed to extend the rack all the way back, like the unmarked brass portrait lens, and image did not seem as sharp. So now i have two cemented (oiled) Doublets without the added extra Meniscus, a Rapid Rectilinear that acts like a Petzval? Is there such a lens? I thought a RR would not have as much of an out of focus area and more over all sharpness and were used mainly for Landscapes.

23-Jul-2015, 20:03
Here is the test image shot with Scientific Lens Company Ocular 8x10 portrait Lens with Castor Oil as a Balsam substitute.
1sec. exposure, My first time using 2 dark slides and wrist action as a shutter. This is a straight scan no adjustments in PS.
I am testing two other unmarked lens's that I hope someone can shed some light on. I will start another thread on these.

24-Jul-2015, 12:18
That image looks good! I think you've got a good lens for portrait work. And it's convertible, too.

I need to make some images from my lens.

24-Jul-2015, 20:35
I am starting another post for the other unmarked lens