I read when searching Google that someone with a Dagor had used it as a long focus lens by removing the front cell.
I tried this with my 130mm and it seems to be true.
Goodness knows what the resulting image taken through the 'converted' lens would be like, I havent tried it with film yet.

There's no reason that it shouldn't work. Each group of a "Dagor" is positive and positioned correctly with relation to the stop to correct coma and (to an extent) field curvature, and is achromatic. The received wisdom suggests that using the rear group alone might produce marginally better results than using the front group alone. You might experience some distortion.

I've also heard about some Dagors being convertable, as many other lenses are also.

I don't know lens construction and designations like some here do, so I can't say other than plasmat designs are deffinitely convertable...

But I have tried a few that I own. Some work and some don't... How well they work is something entirely different But what you see on the GG is what you get on the film!

The big thing to remember is that when converted, the f-stop scale is no longer valid! If you can meter off the GG, it's easy to come up with the converted scale. If not, I'm sure there's a way but I haven't put any thought into it and have not read anything. Could there be a simple multiplication factor? Maybe someone else knows?

When I mounted my claron in an old shutter that had a shorter lens and a F/stop scale for that lens I was told. You can just multiply but the result won't be 100% right. Like I'm ever 100% right-) The proper way is to measure the size of aperture. Not the actual size but what it looks like when looking down the lens. If that makes sense. After listening to alot of back and forth I decided the error that comes from just doing the math isn't enough to keep me up nights.

So to put it into words. If you have a 100mm lens and the scale is marked F/10 that means the aperture at that point is 10mm. So if the lens is 200mm then the same spot on the scale is now 200/10 or F/20. Do the math for all the marks on the scale. It's not a perfect method but it might be close enough.

I believe the factor is 1.7x

So with a 6 inch dagor you get 10.4inch lens.

Multiply the stops the same way. I'm lazy and call it a 2 stop loss.

And keep the taking aperture in the f16 and beyond range when converted.

My personal favorite Anselpic, <A HREF="http://www.hctc.commnet.edu/artmuseum/anseladams/details/frozenlake.html">Frozen Lake and Cliffs</A>, was taken with one element of a Dagor.

Angulons (which are similar to Dagors) are also convertible, although I don't imagine you'd get the best results with the single element.

I have a 210-370 convertible. I removed the front element, and can't get it to focus at 370mm. Just can't get the bellows to extend far enough it seems. I have a Crown Graphic. Thanks.

http://graflex.org/speed-graphic/pacemaker-crown-graphic.html
According to the information posted there the Crown has a maximun of 12 1/2 inches of bellows and 1 inch equals 25.4mm so the longest lens that can be focused at infinity but no closer is 306mm. To use the longer lens on a crown then make an extender lens board, the reverse of a recessed board. A board 3 1/2 to 4 inches extension will let you focus the 370 for close-ups.
Charles

Quote:

On 2004-06-28 13:14, cmaurice wrote: I have a 210-370 convertible. I removed the front element, and can't get it to focus at 370mm. Just can't get the bellows to extend far enough it seems. I have a Crown Graphic. Thanks.

Just for the heck of it

With the old convertibles of which I am very fond, many people just leave the front element on the front and remove the rear element when using the front one. I know that's confusing. But the old convertibles were 'triple' and both could be used individually. Some say to move the front one to the rear when using it alone. I don't bother...

Why do I bring this up? Because you can do that in reverse. Move the rear element to the front of the shutter and try that. You may pick up 2 to 3 inches that way and be able to focus at infinity?

You can also try using the front element by itself. Schneider(sp? it's late) never publicized the fact that the front element could be used, but it can! Although it will not be as sharp as you may like and the f-stops will be slightly different, but it's fun to 'play'.

The rear element is 14.5 inches, so you only need an extra 2 or so. I would first try moving it in front of the shutter and see what happens.

The suggestion of an extension lens board is a good one and you could leave the lens mounted on it permanently. But you'd have to make it yourself which really wouldn't be that hard using two lens boards and a spacer between them...

Out of interest, there's a triple convertible Symmar on ebay right now. I didn't know such a thing existed. Seems to be from the early 50s from the serial number.

Lets us know the auction no of the Symmar.
I expect the speed loss if the Dagor is used 'converted' to be approx 2 stops.
The convertible Symmars seem to lose about that much.

The triple convertible Symmar is a 135/6.8 with individual cells of 210 and 260. It's from early 1952, and it's coated. I've never seen one of these before-- live and learn, eh? Happy Canada Day by the way.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3824203655