Petri Color Corrected Super 1.9

SUCH A CUTIE. I’ve known about Petri for a long time because I love tiny cameras and they make the amazing Petri Color 35 (which as of this writing still does not grace my collection, sigh). If you are looking on the internet for a Petri Color 35 your searches are going to hit a LOT of the much-more-common petri color corrected supers. There are many variants of these, earlier versions have a smaller albada finder with framelines but no parralax correction. Later versions (like mine, commonly referred to as the “Green-o-Matic”) have a parralax-corrected bright-frame finder. There are at least two variations of the bright-frame version that I know of which only differ in appearance. Also notable is the Petri E.Bn (ELECTRONIC BRAIN!!!) which is basically the same camera but with a built-in coupled selenium meter (I think it’s a match-needle set up visible on the top plate but I haven’t handled one so not toally sure). AFAICT all variants came with 2.8 or 1.9 lenses, the 2.8 is much more common but the 1.9 is not exactly rare.

I got interested in this lil cutie mostly just because it looks so incredibly stylish. Much shade is thrown on internet camera websites on petri because apparently the shutter mechanism in their SLRs is unreliable (and they look boring IMO), but several of their earlier cameras are really quite nice and EXTREMELY stylish (this camera, the petri color, the awesome early petri half frames). I really like this camera - there’s nothing really unique about it I suppose but the looks are great, the feel of the winder and the snap of the shutter are extremely pleasing, and it was an easy camera to service.

This is a fully manual fixed-lens rangefinder. It uses a copal leaf shutter that has the “old” shutter speed progression (1, 2, 5, 10, 25, 50, 100, 250, 500) with M and X sync and a built-in self timer. When cleaned up (easy to do) the rangefinder is quite large and bright, and the viewfinder, while not huge, is a million times better than a lot of squinty 50’s rangefinders. The rangefinder patch is big and contrasty, and the eye reief is generous which makes it easy to shoot with glasses on.

Mine showed up with a VERY stiff focusing helical that had an unsettling grindey feeling to it, the self timer was kinda slow/stickey, but otherwise was in great shape aside from 60 years of grime. I was about to return it to the seller and try again on another copy to see if I could get one with a better helicoid, but then my curiousity got the better of me and I started tearing into it. Pretty soon I ordered another one for parts and we were off to the races.

Some thoughts about servicing this camera in general:

• If you attempt to remove the leatherette, it WILL shatter into a thousand pieces and you’ll end up having to replace it.
• Removing the front lens mount requires removing the leatherette, but depending on what kind of service you neeed/want to do you may be able to get away without removing the front lens mount.
• The lens & shutter can be removed by removing the lockring around the rear lens element with a spanner (careful not to scratch!)
• Once you have the whole lens off the camera, the rear element can be unscrewed from the shutter
• The front element also unscrews from the front of the shutter as a single unit. DON’T use a spanner on the ring around the front element that says “Petri”, just grab the whole filter ring and unscrew. The filter ring is actually a trim ring screwed on to the underlying brass lens body. One one of my cameras, the filter ring came off and then I used a spanner on the underlying body, on another one the filter ring stayed stuck and the whole front unit came off with it. When re-assembling, everything I put a small drop of locktite on the inner filter ring threads to keep it stuck to the brass assembly.
• I opened up and cleaned out the shutter. My shutter blades were not stuck but I took em out and cleaned em anyways since I was in there. One note I’ll make is that the flash sync must be set to M to expose the screws on the back wich allow the shutter mechanism to separate from the body (giving you access to the shutter blades for cleaning). Some resources for cleaning the shutter:
  • Good takedown guide with most of the pictures you might want: https://www.photo.net/forums/topic/470076-petri-cc-19-shutter-repair/
  • some very minor differences, but generally useful: http://daniel.mitchell.name/cameras/index.php?page=copalmxv
  • Written for a shutter in a yashica TLR, but it’s basically the same inside: https://ratfactor.com/yashica/
• For fast-moving stuff (bearings in the shutter escapements etc) I use a mix of 50/50 naphta (or ronsonol, or zippo fluid) and nyoil for lubrication. It seems to me that thinning out the oil a bit helps work it down into all the lil places I want it to go. The naptha will evaporate quickly and leave just the oil hopefully where we want it to go.
• For slower-moving things and cam/follower surfaces I use the teeniest thinnest schmear of molybdenum disulfide grease (I just have some automotive grease I bought that will last me the rest of my life).
• I use a lot of naptha to flush stuff out and get it moving, especially parts I can’t/don’t want to remove completely
• Any part I could remove completely (including all the entire shutter mechanism) I soaked in naptha for a while, then ran through an ultrasonic cleaner with water and some general-purpose concentrated cleaner from the hardware store. You can get special ultrasonic solution but I don’t really see the point. I’ve read folks using cleaner like I do, dish soap, ammonia, or some mix of these. DON’T leave unfinished brass parts in the cleaner for a long time (like overnight) because they will start to oxidize.
• After the ultrasonic, I rinse everything in pure alcohol to get all the soap out. My hope also is that the alcohol will dry out everything quickly to minimize the chance of corrosion on any steel screws/springs/etc.
• I cut my own replacement leatherette on a laser cutter, AFAIK no one sells replacement leathers for these.
  • I used Conceria Walpier’s “Buttero” from Rocky Mountain Leather. RM (and a lot of good leather suppliers) will split leather orders for free, you should request your leather to be split to .6mm, which is about the thickness of the original leatherette.
  • I drafted my pattern in a dxf file and transferred it over to svg for some final cleanup and prepping for the laser. The SVG includes a small margin for the laser cutter’s kerf. I’d reccommend making some test cuts and paper patterns before cutting out your nice leather. My pattern is also admittedly not perfect. The lengths of some of the panels are slightly long and had to be cut down with an exacto knife in a couple spots. The really critical bits though (the curve around the lens) are right on though.

Lens Disassembly

The lens and shutter removed from the focus helicoid. The two brass rings with prongs cock the shutter and operate the shutter release. The prongs couple to other prongs actuated by the winder and shutter release. For these to couple and work correctly the shutter MUST be installed with the index mark facing straight up. If the lens is rotated too far one way or the other when installed, the winder will not fully cock the shutter and advance the film or you won’t be able to trigger the shutter (or it will always be triggered).

The lens board removed from the body (you have to peel up the leatherette to remove this). The trim ring (top) has been removed (there are three set screws holding it place). The black focusing ring with the knob is attached to the helicoid by three screws in slots. If you remove these screws you’ll have to re-collimate the lens. I think it might be possible to flush the helicoid out with naptha and work grease back into it without removing this. I opted to just fully disassemble everything and re-collimate to correctly reset the infinity position. You might also be successful scribing a line between the black focus ring and the helicoid it is attached to (and using that to re-align the helicoid on reassembly), but there isn’t a ton of metal showing and I didn’t really realize this until after I had it all apart.

If you do end up removing the lens board, watch for shims under the screws. I’d lay the camera down face up when unscrewing the lens board and carefully watch for any shims. Mine only had a single shim in the upper right corner which I assume was placed there to correct some irregularity in the body.

Picture of the focusing unit & lens board viewed from the top. Behind the lens board, you can see the inner helical through a groove in the outer helical. This groove is where the rangefinder cam contacts the inner helical to couple the rangefinder to the focus. Before disassembling the helical, I noted measurements with calipers between the rear of the inner helical and the rear of the outer helical. I don’t think caliper measurements are precise enough to get the focus set correctly, but at least you can make sure you’re in the right ballpark.

Another shot of the back of the helicoid, looking at the inside of the lens board. The two pins on either side of the inner helicoid engage with grooves on the outer helicoid to prevent the lens from rotating. When you disassemble the helicoid, make a note of the number of turns required to get the pins to clear these grooves, that will help you align all three parts of the helicoid with less trial and error when re-assembling. In this picture you can also see the shutter release arm which wraps around the bottom of the lens. The tab on the far right engages the bottom of the shutter release pin. Another pin (not visible) protrudes forward into the lens and engages the prongs on the brass shutter release ring which rides between the helical and the shutter.

Front view of the helicoid. I scribed marks into the front face of the helicoid to line up with the shutter release pin (at roughly 9:00 in this pic). These scribe marks aren’t precise enough to re-set the focus once the focus ring is removed, but they’ll at least get you close and let you feel assured that you re-assembled the helicoid correctly.

The focus ring (right) removed from the helicoid (left). The two screws on the focus ring bump up against the the upper two screws on the helicoid which form the infinity and close focusing stops. The precise position of the focus ring to the helical sets infinity focus, so if you remove the focus ring you’ll have to re-collimate the lens (or at least feel VERY confident that you screwed it back into the exact same place). Unfortunately you HAVE to remove the focus ring if you want to get the helicoid all the way apart for cleaning. I would also caution you to be EXTREMELY careful removing and re-installing the three on the helicoid (which also hold the shutter cocking ring in place). They are long and break easily, especially if you overtighten them. I had to buy a parts donor because a previous repair job had snapped off these screws. I suspect that an overzealous user could also break them by pushing the focus ring too hard against the stops (probably especially if the focus is super stiff)

A view showing the inner helical (the tall one) and the central helical (with the flange that has screw holes in it). Rotating the central helical counter-clockwise (looking at the front) will eject the inner helical out the back (remember make a note of how many turns!). I would also scribe or mark one side of the inner helical so you know which of the guide pins is right and left before you pop it out.

The helicoid parts fully disassembled for cleaning, from left to right: the inner helical, the outer helical, the central helical, the shutter cocking ring. I soaked these in naptha for a while, swabbed them a bit, and ran them through my ultrasonic cleaner. When re-assembling, it’s important that the inner and central helicals engage in the correct position, which will be pretty easy to figure out if you counted the number of turns it took to eject everything. The fine thread between the central and outer helicals is a single-start thread, so there’s no way to put it back together wrong. I used #10 helicoid grease to libricate these on re-assembly but other folks use white lithium or silicone grease and seem to be doing just fine. Just don’t use too much and remove all the excess once you get things back together, you don’t want it migrating into the shutter.

Collimation

I use Mike Elek’s collimation technique which uses an SLR with a long lens in place of an auto-collimator and a ground glass target taped inside the film gate of the petri. This picture is of the collimation target as seen through the SLR. Collimating is a bit annoying here because the lens unit must be removed to access the screws which pin the focus ring to the helical, but obviously the lens must be installed on the helical to do any meaningful collimation. To get started, I would screw the focus ring onto the helical in such an orientation where you think it will definitely go past where infinity should be (i.e. more counter-clockwise than it started if looking at the front of the lens).

When I feel good about the infinity focus as viewed through the SLR, I mark the position of the focus ring on a lil piece of tape on the lens barrel. This is useful because you must now remove the lens to fix the focus ring in place, and if you bump the focus ring at all you’d have to do it all over again unless you mark it.

Now the tricky part is you need to rotate the focus ring so that it is resting on the infinity stop without allowing the central helicoid to rotate at all. I made this little jig out of some scrap brass. It clamps on to the inner helical (which does not rotate because of the guide pins in the back) and has a finger that sticks down and bumps up against one of the central helicoid screws. Once clamped on, you can loosen the three screws holding the focus ring, rotate it up against the infinity stop, then re-tighten. As long as the screw remains bumped up against the finger of the jig your collimated infinity focus should remain true.

Rangefinder Calibration

The rangefinder mechanism on these seems pretty robust and unlikely to go out of alignment, BUT on both of the copies I’ve handled the rangefinders were badly gummed up by ancient lubricant. I think the main culprit was goopy lube on the post under C. You cannot completely remove that post for cleaning even if you take the front lens board off, because it bumps into the baffle which is cemented in place. If you wanted to get it off you’d have to get the baffle off somehow (probbly solvent? maybe heat?) then glue the baffle back on when you’re done. I opted instead to remove screw C and flush everything out with naptha while wiggling things around then relubricating with nyoil. I suspect that removing screw C is not critical to being able to clean things (although it does give better access and allows for more rotation of the post). The advantage of not removing C is that you wouldn’t have to reset the rangefinder’s infinity calibration which is somewhat fiddly.

This pic is actually from the non-green-o-matic parts camera I bought (albada finder instead of projected framelines) but the rangefinder calibration is the same. I’m not TOTALLY sure I’m doing it right, but my results seem pretty good when checked against a laser rangefinder.

• A is not actually a screw, it’s an eccentric adjuster for the rangefinder cam.
• B is a locking screw which pins the rangefinder cam to the arm which actuates the lens that wiggles the double image around. The small non-removable pin to the right of screw B is the pivot point between the cam and the arm.
• C attaches the cam follower D to the post that leads down into the body. The bottom of that post is connected to yet another cam which tracks the movement of the lens as you focus (which sits in the cutout of the top helical as pictured above)
• D this little arm couples the rotation of the post under C to the rangefinder arm as controlled by the cam associated with A and B

The connection between D and the post under C is just friction, there’s no keying keeping the arm in any particular position. The adjustments made by A and B appear to primarily effect close focus and have little to do with infinity focus. I believe that the precice angle that D is secured to the post by C is the primary means of setting the rangefinder’s infinity alignment.

If you, like me, removed screw C, then to realign the rangefinder:

1. Set the lens to infinity (after collimating if you took the helical apart)
2. loosely screw C into the post
3. use your finger on the rangefinder arm (roughly where A is) to wiggle the arm so that the double image is aligned on a distant object.
4. while holding the arm in that position (I’d keep my eye in the viewfinder the entire time, working on a tripod is advantageous) tighten screw C. This should push D up against the rangefinder cam, and if you manage to keep the arm held in position the entire time, you should end up with a rangefinder aligned at infinity.
5. Check close focus - I calibrated to an object close to the minimum focus distance (tripod and tape measure are your friend). Measure to the film plane of the camera. If this needs adjustment, loosen B and rotate A which will wiggle the cam slightly until you get into alignment. VERY LITTLE torque on A is needed, but on my copies, the cam was effectively cemented to the arm by the enamel used to lock A and B. I dissolved it with naptha (took a while) and (with B loosened) ultimately used a small pair of pliers squeezing between the cam and the spring post above A and B to pop the cam free of enamel that had slipped between the cam and the arm. Once aligned at close range, tighten B to lock the cam into position (gentle! it’s a teeny brass screw and it’s easy to pop the head off!).
6. Recheck infinity focus - large movements of the cam might require readjustment of infinity focus.
7. Measure and check a couple other intermediate distances to make sure everything’s all good.
8. use a tiny drop of clear nail polish or other enamel to lock A, B, and C in position once you’re all good.