G Claron 240mm f9

[Jack the boatman]

Hello,

I have a G Claron 240mm f9 lens without a shutter but with an aperture scale. All the information I can find says that the required shutter is a Copal 1.

I also have a Fujinon W 210mm f 5.6 with what I think is a Copal 1 shutter.

The rear element of the G Claron fits the rear of the Copal 1? shutter, but the front element of the G Claron does not fit the front of the Copal shutter.

Can anyone explain?

Thanks

Jack

[Jody_S]

I have recently fit a 240 G-Claron, older-style Dagor design (52mm front filter thread), into a Compur #1. The cells screwed right in but the thickness was off (I had to cut 2.4mm from the shutter, IIRC). I had several #1 shutters on hand, the cells fit in all of them. I've never had a newer-style G-Claron, but from the pics it looks like the front cell may be larger?

[Dan Fromm]

Look here http://www.skgrimes.com/products/new-copal-shutters/standardcopals for dimensions of Compur/Copal standard #0, #1 and #3 shutters.

Jack, I take it that your G-Claron is in barrel. Is this the case? What is the problem with the front cell? Too large, too small?

[Jack the boatman]

Look here http://www.skgrimes.com/products/new-copal-shutters/standardcopals for dimensions of Compur/Copal standard #0, #1 and #3 shutters.

Jack, I take it that your G-Claron is in barrel. Is this the case? What is the problem with the front cell? Too large, too small?

Dan,

Thanks for your reply, your web site reference is very useful. I'm afraid I can't consider $585 dollars though.

The front cell of the lens is a smaller diameter than that of the shutter from the Fujinon.

I'm not sure if it is in a barrel, I don't think so, I've never seen a barrel lens. The two parts of the lens separate in the same way as my Fujinon and also a super Angulon 65mm. The lens has its own aperture and scale.

I hope this helps

Jack

[Dan Fromm]

Jack. look here http://www.ebay.com/itm/Schneider-G-claron-for-Sinar-Linhof-Arca-Toyo-Cambo-Wista-Deardorff-/190809947746 to see a G-Claron in barrel. Is this your lens?

Measure the outer diameter (across the threads) of your lens' front cell and the inner diameter (again across the threads) of your Fujinon's shutter. And tell us.

I sent you to SKGrimes to get dimensions to check against the lens and shutter you have in hand, not to suggest that you buy a shutter.

[JimL]

If your Fujinon 210 is the older style in a Seiko shutter, the shutter may not be a Copal No. 1 size. It seems that, early on in this lens' production, Fujinon used a shutter size with larger front threads which don't correspond to any of the other standard shutter sizes.

[Jack the boatman]

Dan,

Yes that is my lens.

Sorry, I wasn't assuming you were suggesting I buy one of the Grimes shutters, I was just a bit surprised at the price. I think I only paid about £40 for the lens as it is. I have turned a wooden lens cap, with a view to using it at 1 sec or longer exposures, but it would be better if I could find a reasonably priced shutter.

Thanks again

Jack

[Jack the boatman]

Dan,

I will check the dimensions you suggest and let you know, but it will be Wednesday before I can do that.

Jack

[Jack the boatman]

Jack. look here http://www.ebay.com/itm/Schneider-G-claron-for-Sinar-Linhof-Arca-Toyo-Cambo-Wista-Deardorff-/190809947746 to see a G-Claron in barrel. Is this your lens?

Measure the outer diameter (across the threads) of your lens' front cell and the inner diameter (again across the threads) of your Fujinon's shutter. And tell us.

I sent you to SKGrimes to get dimensions to check against the lens and shutter you have in hand, not to suggest that you buy a shutter.


I have measured as you suggested Dan and the results are:

Across the threads of front element of the Claron lens 38mm

Across the threads of the Copal shutter 39mm.

I have also discovered that the front part of the lens can be separated from the aperture ring part, and this screws into the Copal shutter.
This could give me a usable lens/shutter but with no aperture control.

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?

On the Grimes diagram for the Copal 1 there is a measurement of M39. I am not sure however if this is the dimension I'm looking for, but it does tie in with my measurement.

Jack

[Andrew]

sounds like you tried leaving the front lens cell in the barrel mount and then screwing the whole barrel into the front of the copal shutter?
you've just discoveres that you need to remove both lens cells fron the barrel and then screw them into the shutter

if it's a normal shutter the copal already has an aperture in it and all you need to do is calibrate it to the new lens
you should post a couple of pics of the shutter and if someone has the same lens/shutter combination they may be able to scan the aperture scales which would give you a big headstart

[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

[Peter Yeti]

This scale looks a little odd to me. All my Copal shutters have a linear aperture scale while your steps between f-stops are slightly decreasing.

[Jack the boatman]

This scale looks a little odd to me. All my Copal shutters have a linear aperture scale while your steps between f-stops are slightly decreasing.

Peter,

I'm sorry, you have got the same problem as I have. I have a Copal 1 shutter with a Fujinon lens in it. My G Claron, which is a barrel lens, fits this shutter but the aperture now belongs to the shutter.

The aperture scale that I measured was on the G Claron barrel lens, i.e. the aperture scale of the G Claron.

I devised a method of converting based on the equation relating focal length to aperture diameter, please see above.
This may be of some help to you, but I can't do what you asked originally. Sorry.

Jack

[Peter Yeti]

Jack,

No problem on my side, just trying to help. Bachelier asked you to measure the scale.

The aperture mechanism in the barrel seems different from that of the Copal. The distance between f-stops on the scale only depends on the entrance pupil of the lens and is usually around 5-6 mm for a Copal 1. If you can measure the entrance pupil, you could close down the diaphragm for a few stops, determined by the diameter, and measure the distance on the scale. Since the scale itself is linear, it is trivial to mark all other f-stops.

Even simpler, though, is calling Schneider and ask them to send you the correct scales. Just recently I did this with a Rodenstock lens with wrong scales and got the correct ones the next day. Four little screws later, I had a perfect lens without much fumbling around.

[Lachlan 717]

I'll check mine (late model in black Copal).

If I can unscrew the plate, I'll scan and post it. If not, I'll mark the screw holes and f stops on paper and scan it.

Results soon.

[Lachlan 717]

Here you go. Hope that this helps!!

96347

[Bachelier]

Great ! Thank you very much. I'll try it.

[Bachelier]

Thank you all. I greatly appreciate.