front mounting a B&L 10x12 (210mm) Protar V

[John Schneider]

Has anyone ever done this? I can certainly design the adapter, but I'd like to find out (or calculate) how big a shutter I need so that there is no mechanical vignetting. A Copal 3 is almost certainly too small, but I can use an Ilex 4, Ilex 5, or Compound 5.

[Leonard Robertson]

The "hole" dimensions of a #5 Ilex Acme are: Inside thread dia. (front and rear) 75mm. 12mm deep into the front is a smaller dia. ring which contains the shutter blades. This ring is 63mm inner dia. and about 5mm deep (looks like if the aperture blades were removed it would decrease this depth slightly). From the rear of this ring to the back opening toward the ground glass is 10mm. If you have the Protar in hand, maybe you could make up a ring of cardboard or plastic pipe or something to tape behind the lens board to approximate the rear of the shutter and see how it looks on the focusing screen using movements on whatever camera you are using. I can give measurements for a #4 Ilex if it looks like a #5 is lots larger than you need, but a #4 is quite a bit smaller. Holding up a lens with glass in it, I'm guessing the interior ring is about 44mm inner dia. Of course if a #4 would work, it would be much cheaper and easier to find. I can only think of one larger Compound I have, a #4 I think, if you need specs. on that.

Len

[Tracy Storer]

For the best edge to edge results with the Protar Vs, you'll be stopped down far enough you may not need a shutter.....
However, if you really want to put it in a shutter, I would suggest mounting it "right" in a Copal #1.
Copal 1s are relatively inexpensive, and are better shutters (with much faster max speeds if you really want them) than the big Ilex you'd need to front mount.
You didn't say what format you're using though, so, that'll dictate your real coverage needs.

[John Schneider]

Tracy, I had heard that the elements of a Protar V were too close together to allow mounting in a modern shutter with separate aperture and shutter blades. If not I'll certainly sketch up the adapters to put the cells in a Copal 1.

[Tracy Storer]

John, I'm sure that is true for the shorter focal lengths, but I have a 315 Protar V in a Copal #1, and have seen Protar Vs as short as 140mm in shutters.

Also, definitely confirm that your lens performs as you expect before committing to mounting. (I have a 6" B+L PV that doesn't even come close to what they are "supposed" to do, as well as both B+L and Zeiss examples that cover like crazy.)