dana pionek Posted July 20, 2007 Share Posted July 20, 2007 Hi, I just happened to pick up a really nice Pentax Spotmatic body for a really good price. Upon initial inspection the camera seems near flawless except for one thing - there seems to be some mild corrosion (or maybe gunk buildup from film emulsion)on the film rails (the pressure plate rails are perfect). I assume that this is due to storing the camera with film in it. I ran a roll of film through it and the rails seem to have scratched the film along its whole length near the sprocket holes. Does anybody have any do-it-yourself suggestions on dealing with this problem? I have tried acetone on a Q-tip but didn't get anywhere. My next thought was to cut a piece of glass that would span the two rails then use some spray-tac to attach a piece of 1500 grit sandpaper to the glass and use it in a similar fashion as a block sander to polish the rails. I realize that the tolerances of the film rails to lens mount distance are very critical and I don't want to ruin the camera by taking off too much surface (although I seriously doubt 1500 grit is going to take off that much). Any suggestions/warnings? Should I try the block sanding idea? Send it to a pro to have the problem fixed? Or should I just live with some mild scratching on the film near the sprocket holes? Any help is greatly appreciated. Thanks Link to comment Share on other sites More sharing options...
john_shriver Posted July 20, 2007 Share Posted July 20, 2007 Yeah, sounds like some sort of corrosion. Of course, that area of the film doesn't image. On the other hand, the corrosion has probably increased the film-to-flange distance. Once they are done being polished, the camera can be re-collimated. Probably a small adjustment to the tilt of the mirror to equalize the flange-to-film and flange-to-focusing screen distance. (Well, that's how it's done on a Topcon Super D.) If that's not adjustable, the focusing screen would need re-shimming. Link to comment Share on other sites More sharing options...
donnie_strickland Posted July 20, 2007 Share Posted July 20, 2007 If it was mine, and if it won't show up on the print/slide, I'd let it be. I have a few cameras like this and it's not a problem. Link to comment Share on other sites More sharing options...
curt_saxton Posted July 20, 2007 Share Posted July 20, 2007 Sometimes you'll get lucky using something very mildly abrasive like an eraser for ink, or a tiny bit of tooth paste or automotive paint rubbing compound on a cotton swab. Just make sure it's a TINY bit and you don't get any in the shutter. Link to comment Share on other sites More sharing options...
sw12dz Posted July 21, 2007 Share Posted July 21, 2007 I wouldn't use sandpaper. I have had similar problems with rough film rails and rollers. I used a metal polish (ie: Simichrome or Meguiars Mirror Glaze All Metal Polish) and achieved very good results. Link to comment Share on other sites More sharing options...
luis triguez Posted July 21, 2007 Share Posted July 21, 2007 I wouldn`t use sandpaper either. I`ll try with any gel paint stripper on a Q-tip. You set on the rails, carefully, the gel, and in a few minutes you can take off the corrosion. Maybe you need to repeat a couple of times. I did it this way when I changed the leather from an old Canon with a lot of corrosion in the body. It worked successfully . Link to comment Share on other sites More sharing options...
winfried_buechsenschuetz1 Posted July 21, 2007 Share Posted July 21, 2007 Most camera bodies are made from aluminium (alloy), and uncoated alloy is quite susceptible to corrosion when it gets humid. If the scratches on the film are NOT inside the image frame, I would not bother too much. You might try to remove the corrosion spots with a glass fiber eraser, the thing (formerly) used by draftsmen to erase ink. Link to comment Share on other sites More sharing options...
tony_lockerbie Posted July 21, 2007 Share Posted July 21, 2007 I have used the finest grade of wet and dry sandpaper on some rails and rusted rollers and found it to be very effective. Just be sure to remove all the loose particles carefully before using the camera. Tony Link to comment Share on other sites More sharing options...
dana pionek Posted July 21, 2007 Author Share Posted July 21, 2007 Update - I tried the eraser - didn't do a whole lot for my camera. Was thinking about the car rubbing compound but was worried about getting a bunch of goop in the shutter. I ended up trying the sandpaper idea (only because I had some 1500 grit wet/dry paper laying around) - It worked really well (I lightly wetted the paper and only took a few light/even laps - just enough to knock off the corroded high spots without doing too much to the base metal). I Put a roll of film through the camera and developed/printed it - focus seems spot on and the negatives had significanly less scratching on them. BTW - the glass "sanding block" really helped as far as controlling how even the sanding strokes are. I tried it without the block first and quickly aborted the mission - there was just too much of a chance of totally rounding out the rails. Link to comment Share on other sites More sharing options...
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