In my last entry I shared my experience with a day shooting transmission towers. What I didn't mention was a bit of a problem that reared its ugly head when the negatives were developed. Out of the 10 shots on the first roll I shot that day four were marred by streaks from an unexpected light leak, one of which is pictured above. Additionally when the second roll I shot that day was developed later on a fainter but still frame ruining streak was visible in one of those photos. This is certainly not a situation I'm prepared to live with.
While this came out of the blue and I'm still at a loss to understand the cause of this sudden onset light leak it's quite possibly something that was bound to happen sooner or later due to my lack of upkeep on what I suppose these days would be considered vintage cameras. I own two Mamiya RB67 Pro S's. Both work very well though the one that serves mainly as a backup isn't really much to look at. There is one issue they share that I've been ignoring up until now because it hasn't caused a problem up until now - the light seals, those little bits of foam and felt that keep light from leaking in through the cracks around the doors and whatnot, have been wearing away.
And in the RB67 it must be said there are plenty of places for things to go wrong. In a standard 35mm SLR as well as many medium format cameras such as the typical twin-lens reflex, the big potential for light leaks is around the back door that opens and closes to allow you to change the film. In addition to this any medium format cameras such as the RB67 also have interchangeable film backs that allow you to switch from one type of film to another mid-roll, and the interface between the back and the body is another source of potential light leaks. The RB67 though has still one more spot where things can go wrong. The "RB" stands for "Rotating Back" as this model allows you to switch from horizontal to vertical simply by twisting the back a quarter turn. The feature is more that worthwhile because, if you've never handled a camera this size believe me, it's not something you want dangling sideways from even the most solid of tripods, but it does create one more spot where unwanted light can sneak in.
There are a few tricks to diagnosing a light leak like this. To begin with I should note not all light leaks happen in camera, they can occur afterwards during processing or even before hand. In this case however I noted that the leak appeared in the same spot in each of the frames where it appeared. Since nothing that happens outside the camera would bear any relation to frame spacing this tells me my leak is inside the camera. Second, note that the light streak does not end at the edge of the frame. Since light leaking in from ahead of the back would be blocked from reaching the edge of the film like this by the frame mask that is part of the back this tells us the leak is coming from within the film back itself. Third, since it appears as a hard edged vertical line it would have come through a vertical edge such a the side of the door or the hinge. Last of all since it is at the top of the frame and does not extend to the bottom this tells us the leak is located more towards the bottom of the back since in the camera the image is projected on to the film upside-down.
I'm usually an ambitious DIYer and replacement light seals are not too difficult to fashion from craft store felt and weather stripping foam, but when it comes to my primary camera I'm through mucking about. A complete set of laser-cut seals for the RB67 from Aki Asahi for $12 US plus $4 shipping. I really should have ordered a set for both cameras. On the other hand I've been thinking of trying my hand at restoring my older RB and Aki also does laser cut replacement leather so maybe I'll give that a go. As always I'll keep you posted.
