G Claron 240mm f9

[Jody_S]

This raises another issue in my mind. When the lens is used for its original purpose in its barrel, the distance between the front and rear parts of the lens must be as the designer wants it. If it is fitted to a shutter, is there any guarantee that this relationship will still be optically OK?

This is what I meant when I said I had to cut 2.4mm from my Compur #1 shutter. When the elements were mounted in the Compur, the cells were spaced further apart. I cut the rear of the shutter, as it was easier to do without a lathe, but that meant the aperture was no longer in the center of the gap between elements. Testing showed the lens performed well anyway.

[Jack the boatman]

Andrew,

Yes you are correct.


I have calculated the equivalent aperture for the G Claron when the shutter scale is at f 5.6, f8 etc.

Clearly I cannot expect f5.6 because the G Claron max aperture is f9. This I get when the shutter aperture is at f8. Similarly this gives a conversion for all the remaining apertures.

Does this make sense? see table below.The column headings are as shown . I cannot get them to register with the numbers.


Calibration of Copal-1 shutter for 240mm G Claron

Aperture scale on Copal Shutter. Diameter of circle equivalent for 210mm lens in mm F No. equivalent when using 240mm G Claron
5.6 37.50 6.4
8 26.25 9
11 19.09 13
16 13.13 18
22 9.55 25
32 6.56 37
45 4.67 51
64 3.28 73


Thanks for your help

Jack

[Jack the boatman]

Jody,
Just when I thought my troubles were over. I do some woodturning and have a lathe, but I hesitate to start cutting into a shutter. I think I'll try it as it is and see what results I get.

Thanks

Jack

[Dan Fromm]

Jack, your lens' cells are direct fits in a standard #1 shutter. This means that the cells can be unscrewed from the barrel, screwed into the shutter, and will be ready to use. Oh, and by the way, I've had five G-Clarons (150, 210, 3 x 240) and all of their cells were direct fits in the right shutter.

Don't even think of cutting metal until you've verified that the lens' length, front of front cell to rear of rear cell, is longer in the shutter than in the barrel. And learn more before you do anything else stupid.

[Andrew]

Jack, yes it makes sense, but... it would only be an approximation. I knocked my head against that one for quite a while to understand it because I was swapping lenses between shutters too. There's extra factors to consider if you want to be really accurate because different lenses of same focal length focus the same object at different distances from the film and that means their aperture scales have to be slightly different [!]. The variation in film to mounting flange distance introduced a variable you haven't allowed for.

It seems that the optimal approach is to make new aperture scales by measuring actual light transmission through the lens and the next best thing would be to copy factory fitted scales from someone elses lens of the identical model. I have a 240 g-claron and I could scan the scales if your shutter was the same version as mine is mounted in? I have to assume the scales are correct...

Otherwise you're calculation would probably be a close fit but you'd only know how close by exposing some film and looking very critically at the results. To be a direct comparison I think you'd have to expose a couple of negs of the same subject at the same time with controlled lighting and develop the negs together. I'd also use the one shutter set to the same shutter speed and just swap over the lens cells and adjust the aperture so you don't introduce differences from shutter speed variation from using two different shutters.

I have thought about measuring light transmission by using a controlled light source and a good quality light meter behind the lens but I haven't needed to do the experiment.

[Jack the boatman]

Jack, your lens' cells are direct fits in a standard #1 shutter. This means that the cells can be unscrewed from the barrel, screwed into the shutter, and will be ready to use. Oh, and by the way, I've had five G-Clarons (150, 210, 3 x 240) and all of their cells were direct fits in the right shutter.

Don't even think of cutting metal until you've verified that the lens' length, front of front cell to rear of rear cell, is longer in the shutter than in the barrel. And learn more before you do anything else stupid.

Dan,

I have no intention of altering the shutter in any way, I need it for my Fujinon 210mm.

I have measured the overall length of the G Claron in the barrel and in the Copal 1 shutter. I cannot measure accurately as I don't have a micrometer, but using calipers the lens is actually slightly shorter in the shutter than in the barrel. The difference is no more than 1mm and I think this can be adjusted by easing off the front lens by half a turn.

I hope and I think this has solved my problem, thanks very much to everyone.

Jack

[Jack the boatman]

Jack, yes it makes sense, but... it would only be an approximation. I knocked my head against that one for quite a while to understand it because I was swapping lenses between shutters too. There's extra factors to consider if you want to be really accurate because different lenses of same focal length focus the same object at different distances from the film and that means their aperture scales have to be slightly different [!]. The variation in film to mounting flange distance introduced a variable you haven't allowed for.

It seems that the optimal approach is to make new aperture scales by measuring actual light transmission through the lens and the next best thing would be to copy factory fitted scales from someone elses lens of the identical model. I have a 240 g-claron and I could scan the scales if your shutter was the same version as mine is mounted in? I have to assume the scales are correct...

Otherwise you're calculation would probably be a close fit but you'd only know how close by exposing some film and looking very critically at the results. To be a direct comparison I think you'd have to expose a couple of negs of the same subject at the same time with controlled lighting and develop the negs together. I'd also use the one shutter set to the same shutter speed and just swap over the lens cells and adjust the aperture so you don't introduce differences from shutter speed variation from using two different shutters.

I have thought about measuring light transmission by using a controlled light source and a good quality light meter behind the lens but I haven't needed to do the experiment.

Andrew,
I will try it as it is for now using the calculated values above. There will be inaccuracies in shutter speed anyway.

Thanks

Jack

[Peter Yeti]

Jack,

often the lens elements are made such that you need a shim of appropriate thickness and diameter to mount the cells correctly. This is a means to even out slight variations in both shutter dimensions and cell barrel dimensions. Schneider and Rodenstock (and I guess all other manufacturers) take this very seriously. I would contact the Schneider service, ask for the correct dimensions, measure, and then order the correct shim from them. They also might have the right aperture scale in stock.

[Bachelier]

I've got a 240 g-claron mounted on a copal 1 shutter without scale. Would you mind scanning the aperture scale and send it to me ? I would greatly appreciate.

[Jack the boatman]

I've got a 240 g-claron mounted on a copal 1 shutter without scale. Would you mind scanning the aperture scale and send it to me ? I would greatly appreciate.

Hello,

I have measured the distance in mm from f9 at zero. I hope this answers your question.

f9 0
f11 7
f16 13.8
f22 20.3
f32 27.0
f45 33.2
f64 39.0

If you need any more information please let me know

Jack