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Pete Watkins
25-Jun-2008, 13:46
I'm on the way to mounting my fairly recently aquired 480mm/19" Apo Ronar onto a lens board and front mounting a Copal 3 shutter on the lens. I know that if I try to focus with the shutter on the front of the lens I'll loose two stops so I plan to focus and then attatch the shutter before taking the shot.The big question is would this lens cover 8x10 (I'm pretty sure that it will) and would it cover 11x14 with limited movemnents / any movements/ loads of movements? The lens number is 6592418. I've always lusted after a 355 G-Claron so how would this lens compare to the G-Claron?
Best wishes,
Pete

Bob Salomon
25-Jun-2008, 13:52
The 480mm Apo Ronar in #3 shutter (between the lens as it is supposed to be) covered a 396mm circle at f22. At 1:1 it covered an 18x24" image area.

Don't put the shutter in front of the lens. Do it properly.

Peter K
25-Jun-2008, 14:48
As Bob mentioned before the shutter should be mounted properly. A shutter in front of the lens acts as a diaphragm and will influence the performance of the lens. The result will be at least barrel distortion.

Armin Seeholzer
25-Jun-2008, 15:40
Hi Pete

Even my 300mm APO Ronar MC from around 1998 which is in shutter from Rodenstock covers 8x10 and at f 32 I can shift 1 cm no dark corners!
If I belive the Rodenstock brochure it would not covering my 8x10 but maybe the corners are not at the high Rodenstock standards!
With the 360mm I get about 4 cm shift so with the 480mm maybe you don't have enough shift on your camera!
Much fun, Armin

Pat Hilander
25-Jun-2008, 15:44
As Bob mentioned before the shutter should be mounted properly. A shutter in front of the lens acts as a diaphragm and will influence the performance of the lens. The result will be at least barrel distortion.

So the old LUC style front mount shutters would cause barrel distortion?

Peter K
26-Jun-2008, 00:17
So the old LUC style front mount shutters would cause barrel distortion?
A front mount shutter must be larger as the entrance pupil of the lens. Also too small filters will influence the performance.

It's the same for the rear pupil of the lens, but the difference is, one will get pincushion distortion.

Dan Fromm
26-Jun-2008, 06:05
Peter, are you sure? I ask because I use many lenses, up to a 480/9 Apo Nikkor, front-mounted on a #1 shutter on my little 2x3 Graphics with no distortion or other problems. I wouldn't recommend doing this with shorter lenses on 4x5 because of vignetting; the shutter is effectively an obstruction that blocks outer part of the cone of rays projected by the lens.

Cheers,

Dan

Peter K
26-Jun-2008, 10:00
Peter, are you sure? I ask because I use many lenses, up to a 480/9 Apo Nikkor, front-mounted on a #1 shutter on my little 2x3 Graphics with no distortion or other problems. I wouldn't recommend doing this with shorter lenses on 4x5 because of vignetting; the shutter is effectively an obstruction that blocks outer part of the cone of rays projected by the lens.
Dan, if you are using such a small field aperture as 2x3" with such a long lens like a 480mm, it should be hard to see any distortion because distortions are more prominent in the outer area of the image circle. This is one of the reasons lensmakers are more conservative with the image circle as one can often read here.

The location of any aperture and pupil is very important in an optical system. So the location of the aperture is aligned with realy thin shims the lens is mounted in the shutter. Or a lens made for graphic arts is trimmed for infinity work. But if the aperture is at a completely different location, the correction of the lens is not influenced?

With many double lenses like the Symmar the pincushion distortion of the single parts is corrected. But when only one part is used, also the front part has to be mounted between aperture and film to correct the pincushion distortion of the lens with the barrel distortion made by the front aperture. With other lenses like the older Sironar it's the other way around.

But as often one can read here, ask your lens :)

Cheers

Peter