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View Full Version : what is the downside of f/9 lens elements in an f/6.3 shutter?



stradibarrius
4-Jan-2015, 17:56
Somehow I have acquired a Claron-G 150mm f/9 lens in a Seiko f/6.3 shutter. I have only used it a few times but it seems to work fine.
What if any is the problem with this?

Mark Stahlke
4-Jan-2015, 18:03
The aperture scale will be incorrect.

Michael E
4-Jan-2015, 18:36
The aperture scale will be incorrect.

If the original lens was also a 150mm, the scale is correct. Definitely something to check. You can make your own aperture scale.

Dan Fromm
4-Jan-2015, 19:43
If the original lens was also a 150mm, the scale is correct. Definitely something to check. You can make your own aperture scale.

Not necessarily. Remember that the f/ number is focal length/entrance pupil and that the entrance pupil is the image of the aperture as seen from the front of the lens. Some lenses magnify the aperture more than others.

Liquid Artist
4-Jan-2015, 20:53
If it works fine for you just leave it and have fun with it.

Zndrson
6-Jan-2015, 22:53
I've always been told that its important for the shutter to be shimmed to its lens elements. My guess is that this isn't as important for film as it is an 80 megapixel digital back, but I've got to think it would throw something off at least a little. Am I wrong here?

koh303
7-Jan-2015, 04:58
I've always been told that its important for the shutter to be shimmed to its lens elements. My guess is that this isn't as important for film as it is an 80 megapixel digital back, but I've got to think it would throw something off at least a little. Am I wrong here?


If you can focus, and have a sharp image, it does not matter.

Sevo
7-Jan-2015, 06:08
I've always been told that its important for the shutter to be shimmed to its lens elements. (...) Am I wrong here?

It should not be important on reasonably modern lenses - shutters for photographic taking lenses have been in a small set of standard sizes for many decades, and all reasonable makers have negligible production tolerances for the body strength. If there are shims, they generally go with the LENS, not the shutter, as there is more variability in lenses, where small tolerances in the elements might add up or even multiply. Beware, there are a few shutters (mostly for fixed installation) that came in identical width and thread pitch as some common type, but have a different strength.

Michael E
7-Jan-2015, 15:12
If you can focus, and have a sharp image, it does not matter.

I only know from reading that some lenses were optimized for a certain focus range/magnification ratio with shims.

I have experienced myself that incorrect spacing affects the size of the image circle/circle of definition.

Sevo
7-Jan-2015, 15:47
The lenses, yes. But hardly ever the shutter. If you transplant whatever shims you found with the lens, you'll be fine. If there are none, it either doesn't need them, or they would be missing on any shutter.

Drew Wiley
8-Jan-2015, 09:33
The G-Clarons were apparently designed to focus at f/9. Using a larger aperture might or might not have any effect, in this respect. There will likely be more risk
of mechanical vignetting in the corners of the field. No big deal. We stop down quite a bit to shoot anyway. The biggest risk would be focus shift. I don't know if
it ever was an issue in earlier version of this lens design. It was common with older dagors in big shutters with relatively fast max apertures. If so, just focus at f/9 to begin with.

dave_whatever
8-Jan-2015, 10:05
Not necessarily. Remember that the f/ number is focal length/entrance pupil and that the entrance pupil is the image of the aperture as seen from the front of the lens. Some lenses magnify the aperture more than others.

Yep, when I swapped the cells from a 150mm 5.6 symmar-s with those from a g-claron the wide open position on the g-claron was about a stop away from the marked f/9 position on the symmar's shutter scale. You've got to test and add a new scale in most cases. For shutters with a linear spacing of stops their is quite easy. It's harder on old shutters with an exponential stop spacing.

djdister
8-Jan-2015, 10:21
I picked up a 240mm/f9 G-Claron in a Compur #1 shutter that was meant for a different lens. The aperture scale goes to f5.6, which I calculated was originally calibrated for a 150mm lens. That marked aperture of f5.6 translates to f11 for the 240 G-Claron, so I really need a different shutter altogether. Oh well...

Dan Fromm
8-Jan-2015, 10:33
Dan, skgrimes will be happy to scale your shutter for the lens you want to put in it. Much less expensive than buying another #1.