Old B&L 5x7 lens: Metric or imperial retaining ring thread?

<p>I've come into possession of a B&L 5x7 Tessar, Series 1c, Pat Feb 24, 1903, S/N 3017078, purportedly under license from CZ.<br>

I'm trying to figure out the retaining ring size. The flange thread OD measures 57mm (2.25"). The thread pitch appears to be pretty close to (exactly?) 1mm (or 24 tpi? 25 tpi?).<br>

So would this be a metric or imperial thread? And if it's imperial, do you think a 57mm thread would be close enough not to jam and cause me grief?<br>

Thanks! :-)<br /> Sarah</p>

<p>The type of lens has little to do with the thread needed to retain it on the lensboard. That's a function of the shutter - assuming that the lens is mounted in a shutter.</p>

<p>I suspect from what you've written Sarah, that maybe you only have half the lens. An LF tessar should split into two halves, and if reasonably modern will have threads of 56 or 58mm x 0.75mm on each half. The two halves then screw into a shutter with iris and shutter mechanisms, or into a mounting barrel with iris mechanism only. The whole assembly is then what mounts to the lensboard.</p>

<p>Can you post a picture of exactly what you have Sarah? Because the thread size you've given is nowhere near to any current standard shutter or barrel mounting flange size. See <a href="http://www.skgrimes.com/products/new-copal-shutters/standardcopals">this website </a>for modern and obsolete mounting sizes.</p>

<p>Just noticed the age of that thing. Being B&L, it's likely to be an imperial thread. To make matters more confusing, the modern inch was redefined to be exactly 25.4 mm a few decades ago. Before that it was 25.39xxxxmm. So it's likely that the diameter is 25.25 old inches. A commonly used pitch was 26 tpi, same as the 'modern' Leica thread.</p>

<p>Cowboy, B&L sold Tessars (Ic, IIb) in barrel as well as in shutter. So did CZJ. B&L made lenses to fit US-made shutters that don't conform to the Compur/Copal/Prontor/Seiko standard. "Rochester" firms had their own standards. There's no guarantee that the cells of any lens sold in barrel by, in alphabetical order, B&L, EKCo, Ilex or Wollensak will fit properly in any standard (any of the US ones, note that each US shutter maker had its own standard, or C/C/P/S) shutter.</p>

<p>Also, lens cells threaded M56 or M58 x0.75 are pretty large. M58x0.75 is C/C/P/S #3. There were smaller Tessars (so engraved) and tessar types that fit in smaller shutters and covered at least 4x5.</p>

<p>There's no reliable map from B&L lenses' serial numbers to date of manufacture, but I have in hand a B&L Tessar IIb s/n 3250727 that has to have been made before WW II. Based on lenses I have, 2,000,000 was produced no later than 1915. Sarah's lens was made between the wars.</p>

<p>Sarah, B&L's licensing arrangement with CZJ seems to have ended around 1915. WW I, y'know. After that B&L continued to produce the Zeiss designs they'd licensed before the war.</p>

<p>When you asked about this lens in the crappy old cameras forum you mentioned that you might fabricate a retaining ring yourself. If you're equipped to do that, you should be able to measure too. Go measure. If it comes to that, send the thing to SKGrimes. They may have a stock retaining ring or flange that fits it. If not, they can make what you need. Thinking of which, do you need a retaining ring or flange?</p>

<p>As Dan says, SK Grimes. They have done a lot of work for me over the years and they are top-knoch.</p>

<p>Thanks, guys! The lens is indeed a barrel variety -- no shutter. I'll be lazy and use somebody else's picture -- second one on this page:</p>

<p><a href="http://www.lensrentals.com/blog/2013/10/the-first-annual-photogeek-geek-photo-contest">http://www.lensrentals.com/blog/2013/10/the-first-annual-photogeek-geek-photo-contest</a> <br /><br /> <br /> Rodeo, I had always wondered why the inch would be EXACTLY 25.4mm (and no more decimals). Now I know. ;-)<br /><br /> <br /> Dan, thanks for the historical bits on the lens. I do need a ring, and as I suggested, I might end up fabricating one. I'm fortunate to own a lathe (a tool no woman should be without!). The only problem is that it's currently discombobulated and located in another town. It moves to our new address when my piano gets moved. So it will take some time.<br /><br /> <br /> After some research, I am disappointed to find that 57mm filter rings are 0.75mm thread pitch. I had assumed they would be 1mm pitch and would be close enough to the lens' mounting thread. Rats! I guess that would have been too easy.<br /><br /> <br /> If I find I can't wait for my lathe, I'll keep SKGrimes in mind. Meanwhile, I think you've given me the answers to my questions. Thanks again!<br /><br /> </p>

<p>Sarah - I'll add a bit more here to what I posted over on the Classic Forum. I found two more screw pitch gauges, good Starrett ones, and the pitch on my 5X7 B&L Tessar 1c #3163757 still looks like (probably) 22 tpi. The limiting factor here being my eyesight and the fact that neither of these gauges has 21 or 23 tpi.<br>

I'm impressed that you can cut threads on the lathe. I have a decent 9" South Bend, but I struggle with threading. I think I need to buy some sort of internal threading tool that takes inserts. Sharpening a single point tool to a fine enough point to do camera threads is frustrating to me.</p>

<p>I was curious about the 5X7 Tessar, so I looked at B&L catalogs on Camera Eccentric and held my lens in front of my Sinar (since it isn't mounted on a board). B&L shows the focal length for the 5X7 as 7 1/2"/190mm (early catalogs say 7 7/16"). Focusing my lens on infinity seems to confirm that. I set the camera and tripod at an arbitrary distance from a lamp and focused. With a distance from the focal plane to the subject of approximately 54", the distance from the ground glass to the lens flange was about 8 3/4". I didn't bother to take really accurate measurements, but that gives you an idea how much extension you need if you want to try your lens on your DSLR. Since you mentioned using extension tubes and bellows together, I suspect you already have an idea how much extension you will need. For DSLR use, cutting a hole in a body cap and gluing your Tessar flange to it may work. Usually my wife's Canon 40D is handy but she must have taken it to work today, so I don't know how the size of the Tessar compares with the Canon lens mount.<br>

Len</p>

<p>I have the exact same lens, with the retaining ring (somewhere? not sure where exactly I put the d* thing). It's a wonderful lens, you could not do better with any modern lens unless you wanted to scan your negs with an electron microscope. If you require a more precise measurement, please PM me and I'll find it, and take whatever readings I can with my digital caliper.</p>

<p>I no longer have a lathe, unfortunately I was forced to sell it when I sold my country home a few years back. But if I may comment on the process: some people have said that they can't tell the difference between different thread gauges, because of their failing eyesight; well, your lathe can't tell the difference either. It's easy enough, for a flange, to measure the TPI with whatever gauge you have at hand, then keep cutting on the lathe until the lens fits. It doesn't have to be perfect; it just has to hold the lens firmly when screwed all the way in.</p>

<p>Len, I can sympathize with your failing eyesight. I'm constantly pulling my +20 loupe out of my desk drawer to see such things. So I'll call it 22. Thanks for your improved measurement!</p>

<p>Don't be too impressed with my thread cutting. While I can cut fine threads with a sharp enough bit, I've never done a particularly great job of it. I'm not a particularly skilled machinist. But I do well enough. My lathe is an 8" Grizzly -- a competent enough machine.</p>

<p>I appreciate your researching the fl of the lens for me -- 7 1/2". I had estimated approximately the same from an image focused onto paper, but I hadn't gotten very exact. Most of that distance will be made up via a bellows. I just need to cobble the mount for the EOS flange. And no, it is not possible to mount the lens to a body cap. I tried, and it's too big! ;-) However, anyone who cobbles together lenses should be interested in these things from China for $7.50/set shipped!<br /> <a href="http://www.ebay.com/itm/For-Canon-EOS-EF-Camera-Macro-Extension-Tube-Ring-Adapters-/300667737264?pt=US_Lens_Adapters_Mounts_Tubes&hash=item46013194b0">http://www.ebay.com/itm/For-Canon-EOS-EF-Camera-Macro-Extension-Tube-Ring-Adapters-/300667737264?pt=US_Lens_Adapters_Mounts_Tubes&hash=item46013194b0</a><br /> You get a lens flange, a body flange, and a bunch of tubes that screw together. I'm sure there's a Nikon version too.</p>

<p>Jody, I appreciate your offer, but my measurements are pretty precise. I have heard great things about this lens and look forward to using it. It seems astonishingly good, even towards the edges of the image circle. I don't know whether there's much use/need for a 190mm T/S, but I've thought of using it that way. Eventually I'd like to dip my toe into LF photography, and this might be my starter lens. Before I do that, though, I need to find room to set up my darkroom again. I suppose I might also need a different enlarger, or at least ANOTHER one (as my grandfather's enlarger has too much sentimental value to part with it). My enlarger is a 6x9 (Kodak Precision Enlarger Mod 1 / Assy A). Perhaps I'll have to find an Assembly B head. :-)</p>

<p>I just picked up one of these lenses (sans flange), and am thinking of mounting it for a 3.25x4.25 Anniversary Speed Graphic. </p>

<p>Did you work out a solution? </p>