Oh my! In 2013 there were some comments about vignetting on the photos from Ye Olde Photographer's C-3 which he pretty much dismissed. (Denial is not just a river in Egypt!) Alas, whilst holding the camera to attach a quick release plate for the 2014 Argust Day festivities, he noticed something strange. Inside the lens, the aperture blades appeared to be off center. Worse yet, they didn't appear to move in response to turning the setting dial -- dagnab it! (This also throws a previous test into question, as who knows what the exposure actually was - and any bracketing done by aperture adjustment would have not been doing anything.)

So YOP waded in and started taking things apart, taking macro shots along the way. One observation was a surprising amount of lubricant on the blades. YOP has no recollection of ever going that deep in doing a CLA on the beast, and it's about 57 years old. So don't know if that was the root of the problem, or part of the problem. One end of each aperture leaf engages with radial slots in a ring down in the lens. A number of those were definitely disengaged. The aperture blade assembly appears to be held against the actuator ring by pressure from the two rings that hold the rear lens element in, perhaps it had worked loose. It came out easily, although it did not seem sloppy loose.

So it appears YOP's aging fingers were able to clean off the goo and put it back together successfully.

Of note, this assembly uses TEN curved blades - that's impressive given this was hardly an expensive camera in its day.