Back cell for Ilex Photoplastic 5x7" (and custom made soft lenses)

As i am posting a request for help for the restoration of the camera that came with it, i take the chance for an inquiry about the construction of the lens.
Unfortunately my Ilex Photoplastic 5x7 came with a standard, non inscribed, back cell.
I know that a few other users have the same lens, with different cells.
What's the difference between the three different types?
I am asking about it because i had the guess that it could just be a different "optimization" (read: spacing) of the cell.
Maybe not... but worth asking :)
The idea came to my mind after deciding to "turn soft" a nice 12" f/4.5 Ektar (black, uncoated, on Compound shutter). If i find a rubber ring of the right size, i'll try to unscrew the front element, and re-seat it after placing a shim that would distance it a little more from the second glass element. Still unsure about the width of the shim: is 1mm enough, or still too little to get a very visible "soft" effect?
I am asking because i have experimented with a similar Tessar design, a Schneider Radionar 105mm on Prontor shutter, with front lens focusing. Setting the front lens at min. focusing distance (that's probably more that 1mm difference from infinity) isn't causing a strong softening of the image. I have to retry wide open, though.

Any infos about the Photoplastic back cells?
Any advice about my 12" Ektar project?

have fun

CJ

No answers so far. I'll put it simpler:
what's the max displacement of the front glass in an unmodified Velostigmat Series II 10" ?
Thanks

Habe fun

The Ilex Photoplastic had the standard rear lens + 2 others.
I don't believe the lens could be bought without these two extra lenses.
The regular lens is described as having rectilinear definition, the next one says medium softness and the third extreme softness.

I don't think it has anything to do with "spacing" - the two soft lenses look identical in photos - apart from the engraving on the side.

Quote:

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Originally Posted by cyberjunkie

No answers so far. I'll put it simpler:
what's the max displacement of the front glass in an unmodified Velostigmat Series II 10" ?
Thanks

Habe fun

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for the 9.5 inch, it is about 1/2 revolution. I'm guessing 0.5mm.

Jon

Quote:

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Originally Posted by Jon Shiu

for the 9.5 inch, it is about 1/2 revolution. I'm guessing 0.5mm.

Jon

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So i guess that my original choice of 1mm would be reasonable.
I am basing it on two reasons:
12" is somewhat more than 9.5"
many users "unlock" the Velostigmat to get a stronger soft effect

I'd like to know if anybody did actually try the same thing on a f/4.5 Ektar.
It would be nice to get some more informations before trying: the front glass looks to be held in place by the beauty ring, which has no indents and is stuck by dirt/age.
I don't have a rubber tool of the right size, and i'd prefer to avoid dremeling the ring, only to find out that the lens is not made the way i tought (i.e. the cell can be disassembled from the back).


have fun

CJ

Just to add the 12" Velo 0-5 turns 1 full revolution and about 1.5mm of displacement.

Jon