[Leica] Re: M-6 Pressure Plate Scratches

[Jim Brick <jimbrick@photoaccess.com>]

I remember a few years ago, the FDA found some level of mercury in fish,
taken from somewhere in the Northern Atlantic (I don't remember exactly
where.) All kinds of screams and shouts occurred about the tainted fish,
industrial pollution, and everything else that could be blamed. Then
someone got the bright idea of testing some of the preserved fish, from
that same area, that is stored in the Smithsonian. Low and behold, "all"
fish tested from as far back as they could go (a hundred or so years) had
the same level of mercury. It was naturally occurring and had "always" been
there.

Is anyone "as" exhaustively testing other new cameras? F5, Contax, Rollei?
And is this a new problem "only" because there is a new Nikon scanner? Or
is it a problem that effects your results in other ways as well. Does it
show in a slide screen? Show up in photo prints? Condenser? Diffusion? Cold
Lite?

Drum scanning requires doping the film with a liquid that fills in
scratches and defects. If you've ever sent out transparencies for drum
scans, you will know what I'm talking about. The fact that desktop scanners
(Nikon, Polaroid, Microtec,etc.) are dry scanners and can detect every
possible defect. And believe me, all film, that has been run through a
camera, run through a processor, and handled by humans, slipped in and out
of sleeves, slide treys, etc, has defects. Hence, the goop for drum scanners.

Jim

PS... The thought of having to perform surgery on a new camera seems a bit
out of line.


At 06:03 PM 4/12/99 -0400, you wrote:
>LEICA PRESSURE PLATE REVIEW
>
>Please bear with me as I have not mastered the art of communicating on the 
>LUG net.
>
>A number of persons on the Internet have reported their film being scratched 
>by their Leica M-6 cameras.
>
>I purchased a new one in October 1998 but had not put more than one roll of 
>film through it, and had not viewed it, as it was Kodachrome in a single 
>strip since I intend to make color prints. I put a fresh roll of Kodachrome 
>film in the M-6 and cranked off a few frames. I opened the back and there 
>were scratches beginning at the cassette end of the pressure plate right on 
>to the take-up spool end.  With the back open, I then cranked a few more 
>frames to see if the scratches were being caused by the felt lip in the 
>cassette or something else and there were NO scratches on the film.  The 
>camera was closed up and a few more frames cranked through and the back 
>opened again.  The scratch marks returned.  This indicates the pressure plate 
>was the culprit. 
>
>I examined the surface finish of the flat surface of the M-6 pressure plate.  
>It appears to be approximately the same finish as the flat surface of the 
>pressure plate of my 1966 vintage M-3.  I would like to check the surface 
>finish of each with my Bendix Profilometer (an instrument designed to 
>determine surface finish measured in one-millionths of one inch) but the 
>diamond stylus would damage the surface.  To the eye and fingernail, the 
>surface finish of the radius at each end of the M-6 pressure plate is many 
>time rougher than that of the M-3 pressure plate ends.  Further, the "lay" or 
>direction of the finish is perpendicular to the direction of film travel, 
>which creates an additional source for scratching.
>
>Two brand new pressure plates that I had ordered from Leica in 1988 but 
>unused were also examined.  The radiused ends of the two new pressure plates 
>were much nearer to the surface finish of the M-3 pressure plate radiused 
>ends than is the M-6 pressure plate.
>
>The cause of the film scratches may lie with the comparatively rough radiused 
>ends of the M-6 pressure plate since the radius blends into the flat surface 
>and at that junction, the rough finish of the radius may come into contact 
>with the film.  
>
>If I were to resort to self-help, I would remove the pressure plate from the 
>back plate, and carefully stoke each end of the pressure plate on a piece of 
>crocus cloth glued to a sheet of glass so the factory rough finishing marks 
>are removed.  Just pulling the pressure plate toward you should do the job.  
>Carefully clean the debris away with an ultra sonic cleaner if possible. If 
>the marks have been removed, use some very fine polish to put a nice polish 
>on the ends.  Clean again.  Reassemble the back plate and run a roll of film 
>through to see if there are any scratches.  If none, have a plating company 
>anodize the plate. Reassemble and see how it works for a while.  If there are 
>scratches on the plate, you may wish to "lap" the flat section of the 
>pressure plate on the crocus cloth but it is likely this will create even 
>more problems.  If you are game and wish to risk more problems, place some 
>double sided tape on the back of the pressure plate and cut a piece of wood 
>about 1 ½ X 1 so it will serve as a handle for lapping the plate.  Then move 
>the pressure plate in an arc across the lap but use very little pressure.  A 
>few passes and the high spots should be knocked down.  The work accomplished 
>should be seen in the removal of the black anodized finish.  Once satisfied 
>with the finish, the pressure plate should be anodized.  The plating company 
>may even be able to run the pressure plate though a chemical process that 
>will remove even more of the rough spots before anodizing the part.
>
>This is an involved process and it is the reason why I suggest Leica provide 
>the solution. 
>