I want to mount an Imagon 200 on shutter

[Paul Schilliger]

The recent trend for soft focus lenses has revived an old project of mine: mount ing an Imagon 200 on shutter. That one came originally on Sinar lens board and I made a tube to use it on a Pentax 67. But the angle of view is too narrow for w hat I like to do and I wish I could use it on 4x5 (although it will not fully co ver). I tried mounting it into a Copal #3 but it doesn't fit, the shutter thread is too small. I know some 200 have been mounted on shutters, so what's the tric k? Maybe some Compur are larger than the standard Copal 3? Or maybe there is a s tep-down ring?

[Bob Salomon]

The 200 fits directly into a #3 shutter with no adaptation necessary - at least if it was made in the past 20 to 30 years.

Of course the halation effects at any give setting will be for 6x9cm and not for 4x5. The 250mm Imagon is for 45.

A hint though.

You unscrew the glass from the rear of the tube qand screw it into the rear of a Copal 3.

You unscrew the Imagon engraved ring from the front of the tube and screw it into the front of the shutter.

You throw away the empty tube.

[Paul Schilliger]

Well, thanks, Bob. I guess my sample is 31 years old, for my hands are aching f rom trying to unscrew something from it. I'll have another look in the morning, but it seems to me tha t the ring with the engraved logo (serial number 6326130) and the mounting thread are one single piece of aluminiu m, and if I succeed unscrewing something from the back, the glass elements might just come off.

[Paul Schilliger]

Right, the morning light made it better and I could unscrew the lens element fro m the back with the help of some antislip rubber material (very tight!). It screws directly into the back of the Copal #3 as you mentioned, Bob, but the front tube won't. It is one piece and has a thread of 62 and the Copal inner thr ead is 58. Shall I remove the inner threaded ring from the Copal to find the larger thread? Thanks!

[Paul Schilliger]

I made some test shots today and was pleasantly surprised to find out that this sample of the Imagon 200 covers to about 5x7 without problem. But that was without the specific disk diaphragms, an d maybe with some image degradation at the corners but I could not tell. This brings me to my next quest ion: what differs when using a disk diaphragm instead of the central shutter blades diaphragm? Would I lose much of the Imagon properties by not using the disk diaphragms? I know one thing that will change are the little circles of light around the bright spots but that's not something I will miss. Does the disks contribute to producing the "Im agon effect" or are they merely designed to cut the light?

[Bob Salomon]

If you use the diaphragm you block off the peripheral rays which are important in giving the Imagon effect. That is why the disks are used.

Also we don't say that it won't cover a larger format we stated that the degree of halation will not be what would be expected at a given magnification by using a lens not designed for the format.

[Paul Schilliger]

Bob, thank you again for your enlightment. So, it is necessary that I find a way to mount the front tube on the shutter to hold the disks. Have you been confronted to that size problem before, with the older Imagon?

[Bob Salomon]

No. It should easily unscrew

[Paul Schilliger]

That one is one piece, with 62mm thread.

[Bob Salomon]

Then you should contact Rodenstock service to buy a new front ring.