Well y'all are a lot of help.
I did find some more info, but not Mamiya's directions.
Apparently the greatest soft effect is gained is without disks and at F4.
Spherical aberration was evidently designed in at apertures of F6.3 and larger. At F8 or smaller apertures the lens behaves as a regular sharp focus lens regardless of disks.
The disks are each marked with numbers as shown here; No.1(5), No.2(5.6), No.3(6.3). The number in the parenthesis is, from what I understand, the effective aperture it creates. (When using the rings the normal aperture control should be set to F4.) Exposure control is intended to be done by switching the rings.
So if you need an aperture of 6.3 use disk No.3 and set the lens to F4. You can use the lens aperture control too but, if for example, ring No.2 were installed, stopping down the aperture control ring from 4 to 5 or 5.6 would simply reduce the soft effect not the effective aperture. (I'm sure there is some effect on exposure but it's probably minimal.) Only when you got to 6.3 would exposure be seriously affected.
Each disk also controls the soft effect, not just exposure. This I don't have a good handle on yet.
I'd like to here about the experiences of others with this lens and how you use it.
