Copal #3 (silver) question

[Willie Jan]

Hi,
i bought a imagon 250 in a copal #3 (silver ring).

has anyone got pictures of this shutter with the F ring marked?
Mine has not got the F indication because the imagon does not use it, but i would like to add it so i can use this lens also with the (normal) diafragm without disks.

I did find pictures of the copal 3 in black, but it looks different.

Thanks,

Willie Jan.

 

[Donald Miller]

Since the Copal 3 can be used with a variety of lenses, it requires that the fstop indicator be made for a given focal length lens. In other words, my Copal 3 on my 450 Nikkor M will have a different indicator that yours would have for a 250 mm lens.

SK Grimes can make the specific indicator for your shutter and lens combination.

 

[Jim Noel]

It would be much simpler to mark the scale with the actual diameter of the diaphragm as was done with many early convertible lenses.
Then is is a simple matter of division to determine the f-stop once the focal length and aperture diameter are known.
I had an early convertible in a Compound shutter which was marked in this way. If math skills are a little weak, just do the calculation and carry the info on a card for each lens.

 

[Ole]

The Imagon is one of the simplest lenses to make aperture marks for, since the only lenses are behind the aperture. That means that the f-number is directly given by focal length divided by aperture diameter.

 

[Willie Jan]

Thanks Ole,
i'll start with that.