The late Dean Jones (Razzlwdog) maintained that the variations in performance with early 90mm f6.8 Angulons was often down to cell spacing and that the Synchro Compur shutters they came in had inconsistent "tube length". He posted that he'd machined some shutters to correct length and the performance was greatly improved.
Ian
It's possible, for some combinations of people, lenses and shutters. Or that the latest designs (e.g., SA XL, SS XL) expand the range of person-lens-shutter combinations for which that will be true. Perhaps Nodda Duma can comment.Originally Posted by Dan Fromm
Dan asked me to check out the thread. I'll respond in detail when I get to the house, but suffice to say for now that Ian's correct on principle. "Loose" tolerances on cell position are ~+/- 0.005". That sloppy a value actually makes me cringe. So you gotta maintain your cell spacing---including relative to the shutter.
Typically a precision design will end up around +/-0.002 or 0.001" (inches) on the airgaps. So assume you need to maintain the original spacing to within that tolerance to maintain performance. Aberrations depend on shutter position, so they'll blow up if the airgap is wrong.
Newly made large format dry plates available! Look:
https://www.pictoriographica.com
Interesting conversation. Re my initial post: I found a nice Sinaron S 150mm in a Copal Press Shutter. Since I have no experience with this kind of shutter I thought maybe I could combine the lens with another (fitting) shutter.
Why? What the heck is the matter with the Copal Press shutter? They are very nice to work with with only one small caveat. The Copal Press shutter has a press open lever but the iris will not stop down when using this button (only wide open) so if you want to check shooting aperture on the ground glass you need to use the "bulb" setting with a locking cable release. Not a big deal and the few plus's are 1) no need to cock the shutter w/ the Copal Press shutter so if your banking light (multiple exposures on one plate for same subject like interiors) its a breeze as you don't have to re-cock the shutter chancing moving the camera a bit. 2) Using the press open lever in unison with the bulb/cable you can go back & forth from open aperture to shooting aperture with out changing iris setting once set. This way your less likely to forget to stop back down to the shooting aperture before the actual exposure is made. Does that make sense. They are FINE shutters if in good condition.
Last edited by Louis Pacilla; 16-Jun-2015 at 11:02. Reason: add
I have a similar question. I've got an older Schneider Symmar I bought cheap, the shutter was a mess and the lens is fairly rough, I knew that when I bought it but it got me going. I've since had the shutter serviced but the lens is still a bit rough.
How would I go about replacing the cells, is that (economically) possible?
Well, basically you buy another lens.
People offer Symmars in barrel and as enlarging lenses on eBay. I just did a search for "symmar (barrel, enlarging, db)" and found a bunch, some relatively inexpensive. Schneider's barrels conform to the Compur/Copal standard so the cells are direct fits in standard shutters.
Or you buy another one in shutter.
Thanks Dan. So would I be able to split them from a Sinar DB board too? Interesting, they usually come up quite cheap.
It seems (to me in the UK at least) quite hard to track down shutters on their own ... presumably, then, if one wants e.g. a Compur #1, one simply buys an inexpensive working shuttered lens of any old fl and hopes to flog the cells on to some mug punter while retaining the shutter?
Yep. The DB mount also conforms to the Compur/Copal/... standard.
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