Need "Scan" of f/9 Aperture Scale for 150 G-Claron

[oldlincoln]

I am re-mounting a 150mm f/9 G-Claron in a copal #0 shutter but I need an aperture scale. I could print my own if I had a nice san of a real Schneider one. Can anyone help me out? Helpful suggestions are also welcome.
Thanks, Eric

 

[LJH]

Is this the same as the f9 240mm G-Claron? If so, I can do this in a week or so.

 

[oldlincoln]

I don't know. Maybe others with some experience with the G-Claron group will know and share.

 

[oldlincoln]

I am still needing these aperture scales, can anyone help me out? A new set from Schneider is like 80 bucks. If anyone who has some experience "printing" scales can offer me advice, I would be very grateful for that too.
Thanks,
Eric





Maybe something I do for you sometime?
Vito Corleone

 

[rmann]

G Claron F Stops

On mine it is printed on the side of the shutter, so I can't scan it for you. I have attached a photo - As best as I can measure the distance between stops is 3.5mm evenly spaced. Hope this helps - Bob

 

[Steve Goldstein]

I'll check at home tonight, I have one that I've been planning to sell anyway. There are two basic styles of Copal 0, though, one with a single arc-shaped scale mounting on the front, the other with two scales mounting on the sides as in the picture posted by Bob Mann. Mine is the latter - is that what you need?

 

[chrisaisenbrey]

This looks like a compur shutter. I have the G-Claron 150mm in a synchr-compur shutter.

One option is to take pictures of the G-Claron in Copal (google) and use the time scale to align the aperture.

On mine it is printed on the side of the shutter, so I can't scan it for you. I have attached a photo - As best as I can measure the distance between stops is 3.5mm evenly spaced. Hope this helps - Bob

 

[oldlincoln]

The shutter I need the scales for is a copal #0 with a strip band on the outside of the shutter and an arc shaped band on the front. Both are held in place by two small slot head screws. I'll post a picture when I get home.
Thanks all!
Eric

 

[Steve Goldstein]

I forgot that the one with the arc-shaped band on the front also had a side strip.

 

[L Gebhardt]

Here you go. https://dl.dropboxusercontent.com/u/2175281/150mm G Claron Apertures.tif

A goes on the top and B goes on the bottom.

 

[oldlincoln]

Thanks Larry,
Those don't look like mine but if I can't do better they'll get me by.
A picture of mine

 

[L Gebhardt]

Looks like you have an older shutter. I don't know if the aperture scales are the same between the two styles of copal shutters.

 

[Steve Goldstein]

My shutter is the same as Larry's, so no arc-shaped scale on the front. Sorry.

 

[RalphLambrecht]

Thanks Larry,
Those don't look like mine but if I can't do better they'll get me by.
A picture of mine

View attachment 85214

Does any body understand the matheATICS REQUIRED TO DESIGN THESE SCALES?Inother words,how does one calculate the spacingson the scale,assuming that one knows how to calculate DOF.?:confused:

 

[Ian C]

In answer to post #14

Linear Spacing of Aperture Scale

Note: This assumes that whole stop positions are uniformly spaced along the travel of the aperture lever. This is the case with the lens shutters that I’ve examined.

Let the aperture numbers span a distance s along the flat aperture scale. Suppose that the range of f-stops is r. For example, if the scale began at f/8 and extended to f/64 we’d have 7 whole-stop aperture positions for a range of r = 6 stops.

If the liner distance from f/8 to f/64 was s = 36mm, then the distance between whole-stop positions is 36mm/6 = 6mm. This gives us the generalization

d = s/r

where d = distance between full-stop markings

s = the linear span or travel of the aperture lever from maximum to minimum aperture

r = range of stops (number of stops from maximum to minimum for the lens)



In the case of a lens whose aperture lever adjusts the iris from f/9 to f/64, the range r = 5 2/3 stops or r = 17/3 stops. Then

d = (36mm)/(17/3) = 36mm*(3/17) = 6.35mm [The distance between whole stops]

The distance between f/9 and f/11 is only 2/3 stops, or 2/3 of the whole-stop distance.

[Note: I don’t know the linear travel of the aperture lever for this lens and shutter combination, so the assumption of s = 36mm is fictional but gives us a concrete value for the example.]

d’ = (2/3)*6.35mm = 4.24mm

Let’s see if these distances add correctly.

5*6.35mm + 4.24mm = 36mm

The positions for 1/2 stops, 1/3 stops, and so forth can be worked out similarly.

We could also do this for the angular displacement of the aperture lever if wanted.

 

[Steve Goldstein]

Ian, your post is correct as far as it goes, but doesn't address finding the locations of the starting (f/8 in your example) and stopping positions. The starting position is not so difficult, the stopping (or any usable intermediate point with a larger-than-minimum opening) is more trouble.

 

[Ian C]

Regarding post #16

Yes. That’s another issue. The aperture has to be closed enough at the maximum-aperture position so that it begins to limit the light passed to the film. That engages the diaphragm so that uniform movement of the aperture lever results in uniform changes in aperture and the light transmitted to the film.

I believe that an accurate light meter could be used to find the positions of maximum and minimum aperture value. This would likely require making a fixture of some sort for the lens and meter. Obviously, the fixture must be equipped with some sort of constant-intensity light source.

For a lens whose diaphragm can range from, say, f/8 to f/64 we need only find the two extreme lever positions on a dummy scale attached to the lens and mark them carefully. Then, using the method of post #15, compute the positions for any whole stops or fractional stops as wanted and mark them onto the scale.

Flexible flat scales intended for lens shutters generally have elongated screw slots so that the scale position on the shutter can be fine-tuned so that the aperture passes the correct amount of light. Then the screws are tightened to secure the scale in the proper position.

This process might be made easier by positioning the aperture lever so that the light meter reading for the lens we’re working with matches that of another lens of known accuracy and at the same aperture setting.

For example, suppose you have another lens whose aperture ranges from f/9 to f/64. Place it on the metering fixture and note the meter reading at f/9. Now put the test lens onto the fixture and adjust the aperture lever until the light meter reads the same. The aperture on the lens should now be at f/9 as wanted. Mark the scale at f/9. You could do the same for f/64.

For accuracy, each lens needs to be placed at its infinity-focus position relative to the image plane (maker’s flange distance from the image plane).