I would expect a darkslide slot leak would be some sort of wispy smear that cuts off short of the film edge, and maybe even angled depending on the external light conditions. (But I am working more on analysis than experience here! :( )
As to film, cheap is a relative term! The faster the film, the more sensitive the test, but it's probably silly to go for 1600 or more. I would probably opt for an ISO 400 like TriX, Tmax400, HP5, or Delta 400. If you have to send out (and are in the US) one of the Freestyle films -- maybe Arista EDU Ultra 400 -- that's pretty inexpensive.
Hope you find it soon; that can be pretty frustrating.
Hi. I am interested in this thread because I am also an SQ user. I bought two extra backs to use. One of them had badly decayed seals. I replaced them all with materials I bought from an English supplier I found on the web. I have also used Jon Goodmans products which are excellent. The thing I realised was that there are a large number of seals on these backs, any of which could cause a problem. It wasn't difficult, but more time-consuming than doing a 35mm camera. I would recomend that you get another back in good condition and try that. You can then spend time fixing the original. If that isn't an option, you could apply tape to all joints, including back to body, and darkslide slot, then take a test roll removing one piece of tape per frame to identify which joint/opening is the problem. Alex
I think I may have found the problem? On the back left side, part of it is warped, evidenced by the non-parallel lines. When I push on it, it flexes inward, unlike the opposing side, which is both parallel and snug. Could a leak here lead to the examples I posted? I'm unsure because the film is rolled up in the rear of the back, not "open" like it is closer to the dark slide.
My gut sense is that may not be it, but it would depend on whether light can get far enough past there to bounce around inside. You could put some black tape over that section to test out the theory. That side section is part of the insert. I looked at one of my backs that is handy. On mine there is a rib horizontal across the interior of the insert, between the film rolls, that provides a gusset which potentially makes that side plate rather rigid.
That leaves me to wonder if maybe there could be some sort of structural damage to your insert that is the root of your problem. Are there any cracks in that internal portion?
But then, the side section appears to be a thin outer cover over the inner injection molded part, so I suppose the outer cover might be bowed away from the inner part with an air space between. That may or may not be a problem, hence the encouragement to use tape and test.
The closure around that portion of the back does not use foam seals, just a sort of labyrinth arrangement where a rib on the insert goes into a channel along the back shell which doesn't seem to be very tight, suggesting it's not critical.
(This is another area where some spare modules to interchange could be handy for diagnosis.)
When the postman delivered my Bronica backs first thing I did was checkout the seals and brush out any debris. Next I load up some arista 120 from Freestyle (cheap for testing) then I put the back on the camera and rotate the camera under direct sunlight then start taking some test shots. Any light leaks will show up. I do the same with any new camera.
The only one I had a problem with seemed to have a bent cover or messed up latch. When I closed/latched the cover it would pop back out a little. It created light leaks that were really close to what you have been seeing.
the frustrating part is that when I've tested it, I've taken note of which areas I've taped and regardless it gets leaks anyways. I simply can't find where the light is entering. At this point I might just need a new back.
Originally Posted by DWThomas
Can you clarify what you mean by "cover" and "latch"? Do you mean the hooks underneath the ISO knob? How were they bent?
Originally Posted by donkee
The hooks themselves didn't actually seem bent, could be though that the hooks or the catches were boogered up. Due to it not closing all the way it appeared that the lid/cover may have been bent out a bit too.