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Rick Olson
15-Feb-2007, 21:25
I recently purchased a used 355mm G-Claron and it has a black Copal 3 shutter. The aperture scale runs up to f-90, but the f-stop lever moves past this to what seems would be the f-128 spot. I looked at the lens to see if it was stopping down past f-90 and it was. Is it safe to assume that this could be usable as f-128?

Thanks,
Rick

John O'Connell
15-Feb-2007, 22:07
Looking at mine, I'd estimate that with the aperture shut down all the way, you're past f/128.

I'd also guess that f/128 wouldn't be all that usable on the lens, as you'd have a maximum resolution somewhere in the range of 12 lp/mm. I have used mine at f/90, but prompted by a recent discussion about diffraction here, I looked thru my prints and I can't find any that were taken at apertures smaller than f/45, so I don't know whether I'd recommend stopping down that far.

Capocheny
15-Feb-2007, 23:15
Hi Rick,

My lens also stops down to f90 but moves past the mark into the realm of f128. I've not used the lens at f128.

What you might do is to do some experimentation and see what happens. In light of the previous discussions on diffraction on this forum... I'd say go out and take some shots with the lens at that setting and let us know what happens.

Are you using this lens with 8x10 or larger?

Do you enlarge or do you do contact prints with your negs?

Cheers

CP Goerz
16-Feb-2007, 01:17
Next stop #128!...Diffraction City!! ;-) Best to stick to 64 at max, if you need to use 128 to pull focus either change viewpoint or use a wider lens maybe.

CP Goerz

Mark Sampson
16-Feb-2007, 05:43
Just be sure to post the results in the "wide f******** open" thread.

Rick Olson
16-Feb-2007, 08:46
Hi all,

I will be using the lens for 7 x 17 with contact printing only. I trust that shooting at f-128 (if needed) will have little "visible" impact on the image?

Thanks,
Rick

Michael Alpert
16-Feb-2007, 09:56
Rick,

I suppose you may find a rare situation that demands a depth of field of f128, but the lens is really not very long, just slightly longer than a normal 8x10 lens. Unless you are doing close-up work, f128 will result in an unnecessarily slow shutter speed (better achieved with neutral-density filters or slower film, if a slow speed is what you want) and unnecessary loss of resolution. Even if you are making contact prints and your negative's resolution stays higher than the resolution of your paper, I see no reason to arbitrarily end up with a negative that is not as sharp as it can be.

John O'Connell
16-Feb-2007, 09:58
According to Ctein, people can distinguish print sharpness up to 30 lp/mm. According to most sources, a print requires 5-10 lp/mm in order to achieve adequate sharpness. So if you begin with an image projected on to the negative at 12 lp/mm, you've dropped sharpness almost to the "adequate" level without taking into account the film or the paper. So yes, if resolution matters, there will be visible impact on the image.

A big if, however, is your output medium. In my experience if you print to glossy B&W papers, decreased resolution is quite noticeable. If you print to matte B&W papers, it is less noticeable. If you intend to use alt processes, most of them are limited to resolving 20 lp/mm or less (for ferric oxalate processes and gum--not sure about carbon, but who would be except Sandy?). So for 7x17 on alt process print media, f/128 might be worthwhile, depending upon your intentions.

All of this said, I don't know your work. If you work soft, great; if you're interested in exploring low resolution images, go for it. I personally prefer high contrast close ups done in 8x10 on Pd or glossy B&W papers, so you know where I'm coming from.

sanking
17-Feb-2007, 13:07
Even for contact printing with alternative processes I would never use an aperture of f/128. Even at f/90 I can see a loss of sharpness from diffraction, and it must be a lot worse at f/128. If you find yourself shooting a lot at f/128 with LF you might as well switch to a pin-hole, which will at least give you unlimited depth of field. Or try a Diana or Holga.

For the most part alternative processes like pt./pd that are printed on smooth art papers give 10 lppm or less, with the paper being the limiting issue. Some people have printed pt/pd on fixed out silver papers with matte surfaces and with this method you can get much higher resolution.

Carbon is capable of resolution as high or even higher than silver, though method of printing and final support can result in values much lower. My own carbon prints on fixed out photograhic papers have slightly more apparent sharpness than silver prints because of the dimensional quality of the print. However, the same print transferred to a textured art paper will have much less real (and apparent) sharpness, though other qualities may make it attractive to some.


Sandy King



According to Ctein, people can distinguish print sharpness up to 30 lp/mm. According to most sources, a print requires 5-10 lp/mm in order to achieve adequate sharpness. So if you begin with an image projected on to the negative at 12 lp/mm, you've dropped sharpness almost to the "adequate" level without taking into account the film or the paper. So yes, if resolution matters, there will be visible impact on the image.

A big if, however, is your output medium. In my experience if you print to glossy B&W papers, decreased resolution is quite noticeable. If you print to matte B&W papers, it is less noticeable. If you intend to use alt processes, most of them are limited to resolving 20 lp/mm or less (for ferric oxalate processes and gum--not sure about carbon, but who would be except Sandy?). So for 7x17 on alt process print media, f/128 might be worthwhile, depending upon your intentions.

All of this said, I don't know your work. If you work soft, great; if you're interested in exploring low resolution images, go for it. I personally prefer high contrast close ups done in 8x10 on Pd or glossy B&W papers, so you know where I'm coming from.

Rick Olson
17-Feb-2007, 15:22
Thanks all ... I appreciate the comments. I do not forsee needing to shoot beyond f-45/64, but was just curious on opinions since this is the first lens I have had that stopped down this far.

Thanks,
Rick