[Leica] ROM lenses on the SL

[telyt at earthlink.net (telyt@earthlink.net)]

Up to now the answer has been no they cannot be modified safely to fit
because then the lens would also fit the Leicaflex Standard and SL2, whose
cam followers fo rthe first cam would foul the ROM contacts.... but I think
I've figured out how to do it with minimal modification to the hardware and
full compatability while preventing hardware damage from bad lens/body
combinations. I've run the idea past DAG and he says it ought to work. 

The two differences between the SL flange and the R flange are a slightly
larger inside diameter on the R flange and a slightly shorter bayonet lug
on the body at the 12 o'clock position, with a correspondingly longer
bayonet lug on the lens but (this is crucial) only on those lenses that
would interfere with the SL's mirror. The bayonet lug size change was made
beginning with the SL2 and the longer lug on the deep back-focus lenses
prevents their use on the SL or Leicaflex Standard (where the mirror would 
hit the lens). 

The only ROM lens I've had is the 80-200 f/4 (now 3-cam), which has no
mirror clearance problems. The flange that originally came with the lens
requires the R-only larger inside diameter along with the shorter bayonet
lug for the lenses with no clearance problems. If - a big if - Leica has
beeen consistent about using the longer lug on the deeper lenses, then one
could: 

) put the SL's metering cam on the ROM lens, leaving the ROM stuff and the 
lens' flange alone 

) enlarge the inside diameter of the SL's flange to R specs, leaving its 12 
o'clock lug alone. 

The modified SL would then accept any R lens that doesn't have mirror
clearance problems and would still fail to mount the deeper lenses. The
lens would still be incompatible with the Leicaflex Standard and SL2, so
that the ROM contacts won't be fouled by these bodies' first-cam follower,
but would fit the modified SL and (because of its retrofitted 2nd cam)
meter correctly. Since the SL doesn't use the first cam it wouldn't damage
the ROM contacts. 

The modifications to the lens and SL are both very simple according to DAG.
He milled my extension tube flanges (originally SL-spec) to the larger
diameter, bayonet lugs on the extension tube flanges were not modified, and
my 80-200 R-only flange fits with no problems.  Note that this will not
work with the SL2 or Standard - only the SL.

What I'm missing is a few data points and I'd like the esteemed list
members to help (other list members are welcome to help too).  I need to
confirm the length of the bayonet lug at the 12 o'clock position on a
variety of lenses: SL-spec vs. ROM or 3rd-cam with no clearance problems
vs. any that require the SL2 or newer.  I'm particularly interested in
those that shouldn't be used on the SL.  I don't need a precise
measurement, if you can tell me if the bayonet lugs on your SL-compatible
lenses are shorter than the lugs on the lenses that are too deep for the SL
that's plenty of info.

Doug Herr
Birdman of Sacramento
http://www.wildlightphoto.com

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