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primus96 · Posted: Sat Jun 05, 2004 12:37 pm Post subject:

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.

t.r.sanford · Posted: Sat Jun 05, 2004 1:28 pm Post subject:

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.

RichS · Posted: Sat Jun 05, 2004 2:42 pm Post subject:

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The big thing to remember is that when converted, the f-stop scale is no longer valid!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?

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Nick · Joined: 16 Oct 2002 Posts: 494

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.

Les · Joined: 09 May 2001 Posts: 2682 Location: Detroit, MI

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.

Dave · Joined: 05 Dec 2003 Posts: 78 Location: Canada

My personal favorite Anselpic, Frozen Lake and Cliffs, 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.

cmaurice · Joined: 23 Feb 2002 Posts: 34 Location: Bay area California

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.

45PSS · Posted: Tue Jun 29, 2004 3:35 am Post subject:

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

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RichS · Posted: Tue Jun 29, 2004 4:02 am Post subject:

Dave · Joined: 05 Dec 2003 Posts: 78 Location: Canada

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.

primus96 · Posted: Thu Jul 01, 2004 1:40 pm Post subject:

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.

Dave · Joined: 05 Dec 2003 Posts: 78 Location: Canada

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