Strange problem with my Bronica

[david_henderson]

Once in a while my Bronica SQAi delivers a slide which is

completely , hugely over-exposed. Not just like I got the setting

wrong by a stop or two; but I mean completely white. The next

frame in the sequence is affected too, though only the top half of

it, and the bottom of the second frame is quite normal.

This has happened only with 220 film/back and it has happened

only towards the end of the film- maybe frames 25 on. It does

not happen on every roll.

 

I took the camera/back and all my lenses to the official UK

repairer only minutes away. They looked at everything and

found the shutter on my 150 PS was in need of adjustment and

fixed that. Next trip, several rolls of 220 later, and the problem

happened again. So I'm back off to the repairer soon , with

reminders of how surprised I was when they said it was the

PS150 leaf shutter . However their diagnostic capability is clearly

imperfect. Can anyone give advice about what this is or might be

so I can brief them on what to look for? The problem is obviously

intermittent.

[richard_milner2]

You need to collect more data about the problem. Does it occur when using the WLF rather than the AE finder? If so, this would seem to indicate a problem with the lens shutter.

 

If it only occurs when using the AE prism, that would indicate some kind of problem involving the AE/metering circuitry. For instance, the film-back has a dial on to set the ISO rating. If that dial got knocked, it might tell the camera the film is low speed for a frame or two.

 

I know this is a bit vague. I think you should do some planned tests to try and narrow doen the possible cause.

[david_henderson]

Thanks Richard. Whilst the problem has occurred only with the

AE finder fitted (which it is almost all the time) , I have this set to

manual and set my own calculated exposure using a hand-held

spotmeter. This isn't as I've said a simple metering issue, which

would not result in a complete white-out and indeed would not

affect the following frame either. The problem with setting up a

test is that the issue is intermittent. I might have to use/ process

a few rolls to see the problem once, and many, many rolls to

observe any sort of pattern.

[h._p.]

This is purely a guess but you say that one frame is completely over exposed and the following one is half over exposed. Could the timing be out so that the leaf shutter is staying open too long and the body shutter is also? Then on the next frame, the same happens but the body shutter closes half way correctly giving the impression that the rest of the frame is correctly exposed.

 

Just an idea for you to check.

[justthings]

I had a similar problem with my Rolleicord TLR and what I found was that the leaf shutter was sticking open at slow shutter speeds too and exposing to the extent that adjacent frames where getting additional exposure as well. Initially I felt that the problem was intermittent but then I realized it was consistent and tied to my use of slower than 1/30s shutter speeds. Though I'm not familiar with your equipment it sounds like a similar problem - and it may be simply that your shutter blades need cleaning.

[ptucci]

I had the same problem with my Mamiya 645 pro-I recalled that the fully, completely overexposed frames were when I used MLU with autoexposure. The meter sees pitch black and gives a looong exposure.

[chris_coleman_smith]

Yeah i think i might be having a similar problem at slow exposures on my ETRS. Whats the best way to test this kind of thing or should i just take it straight to a repair guy. If so does anyone know of a good place in the north west of england?

[ken_heflinger]

David,

 

Does the problem happen with more than one lens? Or can it always be traced to the 150 lens?

 

There are at least two possibilities. 1) the lens is not closing the shutter all the way after the shot is taken. This one you should be able to run the camera through it's paces and "chatch it in the act" by looking in the lens as you exercise it. 2) The light baffle / mirror is not dropping all the way in the camera body reliably. As the camera is wound the light baffle is suppose to drop all the way and then the leaf shutter is suppose to open. If something sticks and the light baffel does not drop all the way before the shutter opens back up, the shot is grossly overexposed and it often takes part of the next frame with it because the exposure is occuring while winding.

 

I had a RB67 that had the second trouble. If the camera was wound slowly the baffel would stick and I would ruin the shot I just took. If I wound it quickly it hardly ever stuck. It is possible that you wind your camera more slowly at the end of a 220 roll because it is harder to turn the crank than at the beginning of the roll. So one thing you can experiment with is to wind the camera very slowly with the back or the insert removed and look through the body to see if you see any light coming through the lens through the body when winding.

 

Hope this helps

Ken

[loweskid]

I've had my SQ for over ten years and this has happened to me just three times. I'm almost certain that somehow I managed to remove the lens before winding the film on, hence the mirror is still locked up. I've never been able to do it while actually trying to do it though. I know this should be impossible but I'm 99% certain that on at least one occasion this is what happened. Anyway, they said the Titanic was unsinkable!

[david_henderson]

In case this happens to anyone else I should report back. Ken

Heflinger was closest to the answer.

 

It�s important to understand how the camera works normally.

Basically the camera sits with the shutter wide open so you can

compose and meter TTL. The film is protected from fogging by

the mirror which forms a light-tight seal with the body. So , if you

lock up the mirror, the film would fog unless the act of locking up

the mirror closes the shutter. So that�s exactly what happens.

The shutter closes as the MLU takes effect to avoid exposing the

film.

 

The fault mode here is exactly this. Once in a while, for reasons

and triggers not known, the MLU on this body doesn�t work

properly. Instead of going all the way up it stops part way.

Importantly, when this happens the shutter doesn�t close. So the

mirror�s part way up and light is streaming through an open

shutter, past the half-up mirror, to fog the film. The light strikes

mainly the bottom half of the piece of film you�re about to expose

but the effect of fogging extends to the top half of that frame and

the top half of the frame following -so equidistant up and down.

As soon as you take (or think you take) the affected frame you

wind on and the mirror comes back down. However the damage

has been done before you take, and not only do you fail to make

an image on frame 1 but you�ve also got a half-fogged frame 2

behind a now functional mirror.

 

So how do you get round it till you get a repair? Well your only

chance, outside of ceasing to use MLU, is to hear the difference

when you turn the switch to lock up the mirror. It�s pretty

distinctive but you�ll miss it if preoccupied. When you hear the

malfunction, expose two frames, and start the process again

with the third. The necessary repair is to the MLU

switch/activation. Don�t let them mess around with your lenses

or the shutter control mechanisms in the camera. It�s the MLU,

pure and simple.

 

So how do I know that it isn't exactly as Ken suggested- the

mirror failing to return fully on winding on after an exposure.

Well, only because that would leave me with a black viewfinder

for when I'd be trying to compose my next shot- which would be a

kind of giveaway that something was wrong! I had no such clues