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Steve Beyer
7-Apr-2006, 20:40
The Draw for my camera is 45" that for most practical purposes leaves a standard 1110 lens out. Do any of the Telephoto versions have this type of coverage? HOW MUCH DRAW TO THEY SAVE? IS THERE SOME STANDARD OR SOMEWHERE THAT THIS THE AMOUNT OF DRAW FOR EACH LENS. THANKS FOR HELPING OUT THE NEWBIE....

STEVE BEYER

N Dhananjay
7-Apr-2006, 23:15
Not sure I understand your question. The normal for a 12x20 camera would be approximately 23 inches or so (the diagonal of a 12x20 is about 23.3 inches). That would be well short of the 45 inches bellows that you have. There are many lenses of around that focal length that would comfortably cover the 12x20 format. The long Artars (24", 30", 35") will cover, the 19" Dagor will cover and so on. If you are looking for the longest lens you could use on the camera (i.e., a 45 inch lens), I think there was a 42" Artar. Good luck hunting for it. Even the 30" is rare, the 35" seems even rarer and expensive. The 45" comes around when Halleys comet coincides with the precession of the equinoxes. Cheers, DJ

Michael S. Briggs
8-Apr-2006, 02:08
I find Steve's question clear. He is using the word "telephoto" properly, to mean a lens that focuses with significantly less extension than a regular lens, not as a synonym for a long lens (w.r.t the format diagonal). He wants a lens longer than he could otherwise use with the 45 inch maximum extension of his camera and which will cover 12 x 20.

To be able to focus reasonably closely with a regular, a rough rule of thumb is that you want a max extension about about 20 to 25% more than the focal length. So with an extension of 45 inches = 1140 mm, you are limited to something like a 950 mm lens.

Typically telephoto lenses are able to focus on infinity with an extension of about 70% of their focal length. This figure is called their Flange Focal Length (or distance). So if we imagined a hypothetical 1300 mm telephoto lens, it would probably have a FFD of about 910 mm -- but the exact value would depend on the particular design. This hypothetical lens would work on Steve's camera, focusing to reasonably close distances.

FFD values are published by Fuji, Nikon and Schneider. The only telephoto lens aimed at LF photographers longer than 900 mm that I can think of is the 1200 mm Nikkor-T. It has a FFD of 756 mm, but Nikon rates it to cover only 310 mm diameter. Maybe someone can post their actual experience.

Another possibility might be surplus military aerial lenses. Some of the longer focal lengths are telephotos. But these tend to be quite heavy and probably not in shutters.

Michael S. Briggs
8-Apr-2006, 05:59
You might be in two tripod territory with these focal lengths.

And from your other question, you are just starting with 12x20. You might do better to work with a one or two more normal lenses for a while. Maybe you will find that don't want what is an extra-long lens for the format.

N Dhananjay
8-Apr-2006, 07:31
Sorry, I got confused by the standard 1110 mm - since I have seen standard lens used synonymously with normal lens. I don't think there is any ready and obvious solution for a longer than 45" lens, leave alone telephoto design. Aeriel lenses are the only thing that comes readily to mind. Cheers, DJ

Scott Davis
8-Apr-2006, 08:24
While I am unaware of any lens of a true telephoto design that is in that focal length range, one significant problem with true telephoto lens designs (the flange-focal-length distance being shorter than the nominal focal length) is that they usually project much smaller image circles than their non- telephoto brethren of the same focal length. For example, my Fuji 300T for my 4x5 has about a 215 mm image circle. A Nikon 300 Nikkor-W has an image circle of 420mm. You will probably not find a true telephoto design focal length for 12x20 that would cover. Most people find that when you get into ULF sizes, a "normal" lens for the format feels "long". Get something like a Nikon 450M and see how it feels on the camera.

Eric Leppanen
8-Apr-2006, 09:46
Nathan Congdon reported a few years ago that the Nikkor 1200T telephoto lens covered 12x20 at f/32.

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