Intended use of a large, heavy barrel lens

[Hiro]

The question is originally from a barrel lens collector who hopes to find out the intended use of his new acquisition. Although it would be harder to figure without a picture, I haven't seen it myself and following is the all information I have.

Diameter: 160mm (6.3"), front and rear have the same size.

Length: 210mm (8.3")

Weight: 10+ kg (22 lbs)

Focal length: 510mm (20", measured by projecting an image on the wall)

Open aperture (F): 3+ (calculated by 510/160)

Image circle: 4 feet or more (measured by projecting an image on the wall)

The lens has the aperture but no markings (aperture scale, manufacturer, focal length, etc.) on the barrel. There is also some kind of handle on the barrel.

What could it have been used originally for, a scientific equipment? I seem to remember reading a "huge lens" thread or two (perhaps in association with an auction item?) but couldn't find them by search. I'm not hoping for the lens' exact identification but would appreciate any clue/idea/past thread regarding the reason for its existence.

I bow to the forum's collective wisdom,

[Gem Singer]

Sounds like a processing lens for a lithography camera.

[Ernest Purdum]

It's an intriguing puzzle. An aperture in the f3 range would seem to suggest a Petzval type portrait lens, and some of those do lack markings, but the image circle estimated would be way beyond that of a 20" PetzvaL On the other hand, f3 would be far faster than one would expect of a lens intended for any sort of reproduction work.



Knowing the finish of the barrel could provide a suggestion of its possible purpose. Brass might be an ancient Petzval. Black could be indicative of some kind of industrial item, grey or O.D. a military special purpose unit.



Lack of markings on the diaphragm control suggests that perhaps the intent was to establish the setting by trial, and thereafter leave it alone.

[Struan Gray]

My guess would be a lens for an epidiascope - a large format projector. These tend to be huge, long and fast. No need for markings on the aperture.

Aerial and portrait lenses in this focal length tend to be f4 or slower. f3 is pushing it a bit.

[mark anderson]

i agree it sounds like a lens for a process camera (printing trade). is there any chance the "handle" is conected to the aperature. at the trade school i went to the aperature markings were marked on the lens board, and the "handle was used to change aperature by lining it up with the markings on the board.

if you never saw one i'll give a brief description. the rear standard would be the dark room wall, the ground glass and the film holder are on two large doors that open from either side. film size aprox 24x36". film was held in place by vacume coming through many small holes in the film back.

on the out side of the dark room the carage was about 7-8' long with a copy board to mount the subject in (flat art work or text held under glass) both the copy board and lens board were moved by turning handels inside the dark room. there was a paper tape conected to each marked in percentages. ( for the ratio of reproduction) by setting both tapes to the same ratio the image was already focused.

[Struan Gray]

The aperture is a giveaway: process lenses in this length can't be that fast and still be usable. Projector lenses on the other hand can trade sharpness for brightness.

See Willem-Jan's (http://www.a1.nl/phomepag/markerink/mainpage.htm) site for epidiascope and diascope pages, including this nice Leitz brochure (http://www.a1.nl/phomepag/markerink/epidiask.htm) that explains how they work. See also here (http://spazioinwind.libero.it/gabinetto_di_fisica/ottica/strumenti/proiettore.htm), where the handle on the episcope lens is clearly visible. Willem-Jan was going to try and use his lenses for photography a few years ago, so it might be worth emailing him for any results.

I have seen some of the BIG Zeiss episcope lenses, and they are impressive hunks of glass.

[Bob Fowler]

A couple of questions and comments:

Can you post a picture of this beast somewhere so we can have a look at it?

Was the image you were projecting on the wall something that was at what one could assume would be at infinity focus, or was it something at a closer distance?

Assuming that the focal length is indeed 510mm, just because the front and rear glass is 160mm in diameter doesn't make the lens f/3. What counts is the diameter of the exit pupil, NOT the glass. If it were based only on the glass, my 90mm f/8 W.F. Calter would be f/1.5!

The handle on the barrel... Is it atached to the iris control?

As for speculating what the lens is for, that's really impossible to say without seeing at least a picture or two. It may even be a lens from a large video projector...

[Hiro]

Thank you very much everyone for all the helpful information!

Lithography camera, Petzval, epidiascope, a turret (darkroom) camera with gun control...I didn't know about such things. They sound quite fascinating, and I'll check out some history of optics/photography/printing to satisfay my own curiosity.

Bob, your comments are just. They could change things, couldn't they?

I'll forward the obtained info and comments to the owner, and ask for a photo and some clarifications. I'll post the photo for the curious to see if I get one.

Thanks again!

[Hiro]

Some pictures of the lens have been posted here (http://photo.www.infoseek.co.jp/AlbumPage.asp?key=1266274&un=122566&id=34&m=2&s=0). It's a Japanese language site, but please just click the black "album" box in the frame.

The age is unknown, but it seems to me it could be a relatively modern contraption (makes this off topic?). The collector does own a Dallmeyer f3 (a Petzval variant?), so I guess he collects all sorts of animals.

I aplologize if I created confusion by not confirming the whole truth up front. Here are some clarifications:

- The "handle" looks (in the pics) to be for some way of attachment or a location jig, not a bar-shaped aperture control/pointer.

- Aperture control is done by a small bar coming out from the side of the barrel (visible in the first pic, PICT0665).

- Focal length was measured using a light source at infinity, i.e. the sun, but the distance is from the rear of the lens and not from the rear nodal point. So 510mm is rather the flange back.

- Actual f-number should be larger than 3 due to a smaller "effective" lens diameter.

- The barrel is made of metal.

Adjusting for the method of estimation for both the focal length and f-number, the lens moves at least closer toward the process lens range (or aerial?), and the existence of the aperture seems to support it. At the same time, the appearance resembles lenses used for modern 3-tube (RGB) projectors if a bit large. But would a projection lens have aperture? I'd appreciate any futher comments if the pictures and added info tell you anything.

A frined of the owner is entertaining the idea to use the lens on a big astro camera. I can't envision how big a "camera" it may be.

Thanks,

[Bob Fowler]

From looking at the photos, my guess is that it's a lens from a video projection system of some sort.

[Hiro]

Bob, thank you for the additional comment.

"The aperture in a projection lens" still bothers me. I'll look into it when I get around.

Thanks guys,

[wideopeniris]

I'd say its fairly conclusively an episcope lens. I have a similar one here, a Meyer Epidon 420mm f3.6. Same sort of size. It came from a 'pentascop' which looks like a zeiss machine rebadged.

Episcopes use a lamp to illuminate a solid object or a photo in print form etc. Because so much light is lost in reflection, the lenses are as fast as possible in order to keep the illumination down to manageable levels. Even so mine has 2x 1kW lamps for a 5x7 size target! Some of the leitz episcope lenses are truly huge (eg 1000mm f3.5 280mm diameter)

The lens seems to make a nice image on the wall, but I'd be interested to know if anyone knows the formula or the properties of these lenses. Shining my HeNe through it reveals its a triplet design. Has anyone tried seeing what its performance is like as a taking lens for portraiture (right sort of magnification ratios)??

Kevin.

[Ash]

Hmmm.... a three-year-old thread, I think the original poster will have moved on from this issue by now! :)