Hi to all,


I have a 360mm Imagon in a Compound 5 shutter lying around for quite some time and now want to start using it.

I guess I have read every possible thread concerning the use of Imagon lenses, but I must have missed something essential, or I am completely lost in outer space.

The lens has the 3 original disks :

H 5,8 – H 7,7
H 7,7 – H 9.5
H 9,5 – H 11.5

I am aware that we are talking here about H-stops, not F-stops. (whatever the H stands for)

1) My question, in terms of light measurement, what F-stops do the H-stops correspond to ?


2) In order to use the Imagon lens without any of the three disks, but using the diaphragm of the Compound shutter, it would be useful to calibrate the F-stops settings.

The maximum opening of the shutter being 64mm, according to the F/D rule, this would give us a maximum aperture of 5,6.

Am I right in applying the same rule to determine the respective F-stop ?


3) Let’s now come back to the 3 original disks :

H 5,8 (center disk and small disks open) – H 7,7 (only center disk open, opening 38 mm)
H 7,7 (center disk and small disks open) – H 9,5 (only center disk open, opening 31,5 mm)
H 9,5 (center disk and small disks open) – H 11.5 (only center disk open, opening 26 mm)

If I apply the same F/D rule to the 3 disks with only the center disk open, I would obtain the following F-stops :

360mm / 38mm = F-stop 9,47
360mm / 31.5mm = F-stop 11,43
360mm / 36mm = F-stop 13.85

The F-stop numbers have strange similarities again with the H-numbers.

Is this reasoning correct, or am I wrong ?

4) Does someone out there have for sale the book from Alfons Scholz on the Imagon lens ?


That’s it. Hope you could follow my reasoning.

Thank’s in advance for your help.


Thierry