Dallmeyer f/6.5 Wide Angle lens dimensions ?

[John Hancock]

I recently got a Dallmeyer f/6.5 Wide Angle lens, the 2.375" (~60mm) version. It came in a Size 0 Synchro-Compur shutter.

The lens mounting diameter, as manufactured, is 31mm for mounting in a flange.
This one had been machined down and re-cut to fit the Size 0 shutter. Due to the thinness of the remaining metal, some thread and length of the mount tube was lost, over at least part of the circumference.

I am just curious in case anyone is in a position to tell me what is the specified distance of the rear cell from the rear mounting face of the Dallmeyer assembly ? (I doubt if any loss is sufficient to cause significant optical degradation at the small stop apertures that I use.).

I will be mounting the lens on a Size 0 Epsilon shutter (re-built from 'parts' scraps), in which I have ground away an internal bevel, in the mounting tube, to minimise geometric vignetting by the shutter structure.
(This is copies the bevelling of the shutter used in my Envoy Wide Angle camera. That camera uses the optically-similar Taylor-Hobson Envoy Wide Angle f/6.5 64mm lens. The latter however is factory-manufactured to fit on the front of Size 0 shutters.)



[I have found a previous thread with some related data here
http://www.largeformatphotography.in...4inch-MOUNTING
just for information]

[Dan Fromm]

John, I've been fascinated by that class of lens for years, have wondered how people made them usable. I'd speculated they might be front mounted on a #1 via a threaded bushing. That someone would turn the rear tube down to fit a #0 never occurred to me. I've always thought that the ancients used them on large behind the lens shutters or on cameras with focal plane shutters.

Strong suggestion. Put the lens back together, screw it into the #0 Compur, mount it on your camera and see what sort of image it puts on the ground glass. I understand that this is a poor way to evaluate a lens, also that the lens was made to be focused wide open and shot at much smaller apertures. The VM suggests stopping down to at least f/11, says that f/22 is better. I'll bet that the lens' tube length wasn't reduced when the tube was turned down.

What format do you want to shoot it on?

It took me a moment to understand why you'd want to grind an internal bevel in the shutter's rear tube, then I did a quick calculation and saw the possibility of mechanical vignetting. I don't think that y'r bevel will solve the problem. My crude model, which isn't particularly good, says that as long as the shutter's tube length is unchanged (20 mm) vignetting will prevent the lens from covering even 2x3.

I had a similar problem with my little 60/14 Perigraphe Ser. VIa. Its barrel is too wide to fit a #0 or even a #1, the likely shutter for front mounting it was an Ilex #3. The Ilex 3's tube length is 1.025" and the model said it would prevent the lens from covering even 2x3. I had SKGrimes cut an Ilex 3's rear tube off more-or-less flush with the back of the shutter and drill and tap holes in the back of the shutter body for holding the shutter to a board. Set up this way the lens gets full coverage with no mechanical vignetting by the shutter.

You may have to resort to similar heroic measures to get all that y'r little Dallmeyer w/a can give.

[John Hancock]

Dan, Thank you for your fast and informative response ( I was hoping it would catch your eye !).

I do indeed intend to go ahead with the assembly - I just thought I'd get the question out there before final assembly, as fresh scenic opportunities are a bit limited in February unless I have occasion to travel somewhere.

I'm going to fit it to an adapted, pocketable, 120 film 6x9 camera which I have already test-driven with the TTH Envoy borrowed from my Envoy Wide Angle camera.
This for example is acceptable to me for a February day using Portra 800 at f/22. If you click on the Flickr image you can 'pixel-peep' - that renders well on my browser/screen.
Oh, I have to admit, the Lab's scanner cut a bit off the frame - I'll have to do a full scan on my flat-bed ...



'6x9' is right on the limit for both lens installations, due to the shutter structure vignetting. (I read that the Dallmeyer, and I would expect the Envoy, would cover more in a 'proper LF camera' mounting.)

By 'on the limit' I mean when I can just see the light 'disc' unobscured by camera/shutter furniture, at f/32 or f/45 as the case might be, close into the corners of the film gate. Obviously, at wider apertures I would rely even more on film latitude as a larger fraction of the light would be obscured.
Here is a picture of the camera (before black-painting the bevelled surface of the shutter). More details may go on to Flickr after I have some results with the Dallmeyer.



Looking forward to seeing how the Dallmeyer compares with the TTH !

I'm going to stick with the Epsilon shutter, which works fine (I'm happy with these, having used or brought a few 'back from the dead', I don't need a delayed-release timer). The Synchro-Compur was not 'bevelled' (which would have limited it more on its LF host), and I'll not modify it, so it will remain a nice shutter for LF use with a longer focal length lens.
EDIT: Oh, the mounting tube of the Epsilon shutter was shortened (as far as possible) during the bevelling. (As was also done in Envoy WA camera manufacture.)

I will certainly bear your suggestion, to cut off the mount tube and bolt directly to the lens standard, in mind! If I like the lens, there's nothing more to lose further cutting the Epsilon about. To get the full benefit I might also have to shorten the camera helicoid and its furniture a bit more. I'll just get the results as presently configured first.

[John Hancock]

I've also played around with the 75mm Tominon and Ysaron out of curiosity, which taught me that the #1 COPAL and PRONTOR are not nice on a small camera . And of course the TTH Envoy is better for that sort of job anyway.

[Dan Fromm]

John, thanks for the two replies and kind words.

You're a braver man than I am. I'm not sure I could manage replacing a 6x9 folder's bellows, front door etc. with a plate as you've done.

I use essentially two 2x3 cameras. 2x3 Graphics, Speed and Century/Crown (yes, that makes two) and 2x3 Cambo SC-1. Both accept #1 shutters and even Ilex #3 with no problems. But they're not that small ...

Good luck, have fun and please tell us how well y'r 60 Dallmeyer shoots and whether it is as good as y'r 64/6.5 TTH.

When I was building my kit I badly wanted a 64/6.5 TTH ex-Envoy, never found one I could afford. I now have too many decent 60 mm +/- lenses that cover 2x3 to be able to justify getting more but still wonder about the TTH. They made such good lenses ...

[John Hancock]

Dan, Thank you again. I did start my mucking about a few years ago with a rail-bed folder, but for wider angles the opened bed door got into the field of view , this one is not too clear from the thumbnails, it was actually a bakelite meniscus lens camera, with the curved film gate replaced by one from a scrap Billy Record. The well-built helicoid was its 'sale point' for me. Well, it keeps me amused. I'll post here when I have any further progress to report.
Thanks again, I only recently signed up here, but I've profited from your postings on other forums.

[Roger Hesketh]

Hi John I have a 60mm Dallmeyer too and I also have a number of other TTH and Dallmeyer lenses of that design. The smaller ones up to 133mm all have the same thread 31mm. I have a threaded bushing to allow them all to be front mounted to a Compur shutter. The problem I found with the 60mm was not vignetting caused by the shutter but the extra extension that the shutter added to the set up. With many 2x3 cameras it makes it impossible to achieve infinity focus.The lens cannot be brought sufficiently close to the film to allow infinity focus. For instance I think on a miniature speed graphic the only way the 60mm lens can be made to come close to infinity focus is if it is used unshuttered and on a flat board. Even then it does not quite make infinity focus but will focus just and only just as far away as the hyperfocal distance if the lens is used at small stops. Distant subjects can then be rendered just sufficiently sharp if the lens is stopped right down. I seem to remember the lens could be used shuttered on a Century Graphic. There is nearly 5mm difference in focal length between the Dallmeyer lens and the TTH Wide angle lens. So you are not comparing like with like. I would caution you to check that you can achieve infinity focus with the set up you intend before you make too many modifications. The lens has plenty of coverage and will cover quarter plate at f16.

[Dan Fromm]

Roger, since you mentioned 2x3 Graphics, here are their minimum extensions:

Miniature Speed Graphic, 58.7 mm
Pacemaker Speed Graphic, 61.9 mm
Pacemaker Crown/Century, 34.9 mm

When you factor in the extension a shutter adds, whether the lens is in or on it, its easy to see why even old-style 65 mm lenses (65/6.8 Angulon, 65/6.8 Optar/Raptar, and those UK-made lenses that are really scarce in the US) in or on shutter don't work on Speed Graphics.

More modern lenses, e.g., 65 Super Angulons and Fujinon SWs, also 58/5.6 Grandagon/Technikon and 58 and 60 mm lenses for Koni-Omegas focus through infinity on 2x3 Speeds. I'm all for tinkering so wouldn't push anyone who wants to play with older w/a lenses for 2x3 towards modern ones, but modern ones are not without their advantages.

I shouldn't have added confusion by mentioning my Graphics. John has a properly short camera.

Cheers,

Dan

[John Hancock]

Roger, Thank you for your reply. As you say, the Dallmeyer does need to sit further back than the Envoy; measurements of lens standard positions agreed with the difference in specified focal lengths, not that I was in any doubt.

The beauty of this camera hack is that the helicoid (shortened) can be screwed in so that the lens standard could be well INSIDE the camera if there was an even shorter length pancake lens (I don't know of one) that I wanted to fit (I wouldn't) .

I will post the build details in due course. However, to summarise, it's based on the Wembley Sports / Arti-Six (they're the same - different marketing) bakelite camera which has a very nice helicoid lens standard that screws directly into the body. (It doesn't 'wobble' like some of that sort do). The helicoid has multiple threads so it is possible to choose a position where the click-stop for Infinity is close enough to correct for whichever lens is fitted.

[John Hancock]

As a parallel activity I'll prepare a subassembly, from spare bits, that follows Dan's suggestion of cutting the mount tube off a shutter base and bolting it to the lens standard face. I've got another helicoid with a large hole (previously used with a #1 shutter) which will do nicely.