150 G-Claron for 5x7

[Kevin Klazek]

I have read in this forum that the 150 G-Claron works very well on 5x7 with lots of movement when stopped down. Sounds like a good medium wide angle. My question is , if I buy it as a barrel lens, can I just drop the elements into a copal-0 (from a 5.6 symmar-s 135) with no other modifications (shims?). Assuming that is all I need to do mechanically, what are the issues with the apeture scale. What are the fixes for the scale issues.

Thanks

Kevin

[CXC]

Check www.skgrimes.com for detailed info about mounting specific lenses in shutters.

By the way, G-Clarons are readily available on the used market already mounted in shutters, at reasonable prices.

[lee\c]

I use a g claron 150 on my deardorff 5x7 with movements no problem. the cells drop right in to a copal #0 without shims but please remember these 150's are f/9's. I sent my copal #0 to skgrimes and they cut new f stop numbers for me for $45 plus shipping.

leec

[Paul Ewins]

Kevin,
I've done exactly that, but don't know myself whether it really needs a shim. As for the aperture scale, all I did was glue a piece of paper over the exisitng scale and write in the new values. The formula to calculate the values is focal length / apparent aperture. Some lenses have a magnifying front element, so you need the apparent aperture not the actual aperture.

The method for obtaining the apparent apertrure is something like this:
In a dark room or corridor set up a flashlight (battery torch) so that it shines horizontally.
Open the aperture right up and place a piece of ground glass or wax paper as close to the front element as practical.

Hold the lens with the front element towards you and the light from the flashlight shining through the rear of the lens. Now measure the size of the circle of light on the ground glass, this is your apparent aperture. Now compare this to your actual aperture and you will have the magnifying value. You can now compute a set of f-stop values using the formula: focal length / (actual aperture x magnifying value).

The one thing I'm not sure about is how the rear element effects the formula. I've got an old Caltar 210/f5.6 but no matter how I computed it I couldn't get the maximum values to agree.
Having said that, I don't think the G-Claron has a magnifying front element (or rear element), so you can just use focal length / aperture. You are still stuck with F9 because there is a baffle on the back of the lens group that restricts the aperture, regardless of how wide the iris in the shutter will open up.

Take a micrometer, a cheap plastic one will do. Set it to the value for the f-stop you want. Put the micrometer jaws inside the shutter and - gently - move the aperture lever until the iris touches the micrometer jaws. Now mark the f-stop on your paper scale and move on to the next one.

Hopefully somebody will correct any errors in all of that. When I get home I will dig out the calculations I did for my own G-Claron and just give you the actual aperture sizes for each f-stop.

[Kevin Crisp]

I've taken three of them and put them in copal 0's over the years. On every one I had the spacing was exactly the same as the barrel mount, no shims were necessary. Yes, you can get quite a bit of movement on 5X7 with these. I've never felt the f:9 was a particular problem for composition and focussing but some people think it is.

[Jim Galli]

My experience is that I can find the edges once in a while with the deardorff 5X7 but still consider it an excellent or better 5X7 lens. Yes it goes right into the Copal 0 shutter with no machining or shims unless it has shims to begin with. Your scale will be about 1/3 stop off. You could almost elongate the attachment holes from the 135 5.6 scale and move it over a third stop. Think of it like this. 135 f10=13.5mm 150 f10=15.0mm. You need to open 1/3 stop all the time to be getting the advertised with the 150. It'll drive you crazy.

[Kevin Klazek]

Thanks to all for your input. Jim, I like your solution to the apeture scale issue. If I understand you correctly, I would need to add 1/3 stop to the exposure to get the indicated reading. In other words to get an f32 setting , I would have to set the scale pointer to f22 and 2/3. I also have a dorff 5x7. I am using my 4x5 90SA and symmar-s210 for 5x7 lens. The 150 should fall nicely in between.

Kevin