Need help with a Hassy (500CM) Leak

Ariston

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I replaced the light trap on all of my backs, but just shot another roll through one and still have a leak. Now I realize the leak is not on the side (where the light trap is) but on the bottom. It is also not affecting the very top of the frame, just below it. It is consistent across multiple (but not all) frames. What would cause this? I should mention that I opened the back prematurely because I thought it was a different back - but that should also leak on the sides, not the tops, right?:

 

campy51

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It looks like the trap dislodged when you put the dark slide in. It happened to me the first time I replaced one.
 
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Ariston

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campy51 said:
It looks like the trap dislodged when you put the dark slide in. It happened to me the first time I replaced one.
Click to expand...
I’ll check, but it seems to me the leak would be on the side of the film if it is the trap since the trap is located on the side...
 

Philippe-Georges

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The image is exposed upside down, the rule of optics.
It's most likely a flair caused by a leaking light trap in the film chassis.
The light trap is on the left side seen from behind. So, if the image is shown correctly, the flair is on the right side.
Don't forget that the light leak doesn't stop at the end of the frame. If you walk around without the protective slide put in, the light will (slowly-) penetrante and flair the film regardless what frame is exposed or ready to be exposed.
The light trap is the most vulnerable and weakest part of the Hasselblad V and when damaged, it gives the weirdest and unpredictable forms of flair. To my experience, that plastic trap lasts for an average of 5 years, in a 'normally' used film chassis (and keep the slide clean as it might bring dirt into the trap and hurt the plastic).

Get that film chassis repaired (it's worth it), and have the camera body checked too, just to be sure, and also: "always use your thumb to save the heels" as the great David Odess used to say...
 
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Ariston

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I am still not understanding. I am looking at my A12 back right now, and the light trap is on the SIDE, not the bottom (or the top). The light leak is at the top of the image, which means it is at the bottom of the film back. Even if it were leaking in from the side, it should be much brighter the closer to the side it is, which it is not.

I am not trying to be difficult - I genuinely do not understand how the negative I posted above can have a light leak from the side...
 

MattKing

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The light leak may be at one end only of the light trap.
 
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Ariston

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MattKing said:
The light leak may be at one end only of the light trap.
Click to expand...
Yes, but wouldn't it "bleed" in and be much brighter toward the edge. I actually just took the back apart, and the new light trap is still installed correctly. Maybe it is a bad light trap somehow, but I can't see any defect.

I guess it has to be the light trap - I don't know what else could fail. I installed three of those things, one on each of my backs. It's also a little weird that it is leaking in a little below the top of the frame.
 

Philippe-Georges

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The ways of the light are unpredictable...

I could show you several negatives with flair from leaking light traps having the weirdest shapes, yet still, changing the trap and trouble was gone.
 
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Ariston

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Philippe-Georges said:
The ways of the light are unpredictable...

I could show you several negatives with flair from leaking light traps having the weirdest shapes, yet still, changing the trap and trouble was gone.
Click to expand...
I think it has to be. I'm going to try one of the other backs I changed the trap on. If it leaks too, I bought faulty traps.
 

itsdoable

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One of the ways to narrow down the location of the light leak is to take the lens & dark slide off, lock the (secondary) shutter open, hold the camera up to your eye and look into the mirror box such that you block off extraneous light, and us a small bright flashlight around the film back - body interface to locate the leak.

The sharp line on the light leak pattern is the shadow of the film gate when light leaks in from between the film back and body.
 
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Ariston

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itsdoable said:
The sharp line on the light leak pattern is the shadow of the film gate when light leaks in from between the film back and body.
Click to expand...

See, this is what I’m wondering about. There is nothing to change or fix when it comes to the mount between the back and the body. There are no seals, just machined grooves. The back seats onto the body well. What could the problem or solution be in this case?
 

MattKing

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There is something between the back and the body - the channel for the dark slide. It is just that it is built in to the back.
 

itsdoable

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Shine the flashlight into the dark slide slot, and/or the film back - body interface, and determine where it's coming from first.

The dark slide slot is in the film back, ~1mm from the back - body interface, but light leaking in there will also cast a shadow like that.

The mechanical light seal channels on the back/body interface are quite shallow, and any looseness on that interface can result in a light leak. Of if you got something stuck in the channel that prevents the back from sealing properly.
 
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Ariston

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Thank you for that! I followed your instructions, and light was in fact leaking out the bottom, just as I suspected. I'm not sure what to do with it. It is a pretty beaten up back, but it's all solid metal. Checking it closely, there is an ever so slight amount of play. I had a hard time even holding it firmly enough against the camera to prevent the light.

I may put some thin tape on the bottom, but I don't want to mess up the tolerances with regard to my other two backs. I may try to hammer the hinge slots down some to tighten the mount...


EDIT: I can see it. The two hinge slots are VERY slightly bent, like someone tried to pry the back off. I may try to find a donor back if I can't figure out a way to hammer those straight.
 

John Koehrer

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Are the metal fingers that hold the back in place bent down a little bit?
 
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Ariston

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John Koehrer said:
Are the metal fingers that hold the back in place bent down a little bit?
Click to expand...
No - luckily it is just the little hinge tabs on this particular back. I checked the other backs with a flashlight, and they were fine. I was worried about that.
 
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Ariston

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I want to provide a photo in case future visitors of this thread have this problem. The two hinge tabs on this back plate are very slightly bent, keeping the back from seating securely. If I can find a donor, that plate is easy enough to replace. I may try straightening it myself, if I get brave. Not knowing what I was looking for, it was easy for me to miss this:

 
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itsdoable

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Slightly bent tabs are normal for old back. Underneath those tabs, there should be a thin spring-steel shim that helps hold the back tight to the body at the bottom.



This back is from 1993, yours if from 1983, so it may be a little different inside. The interlock mechanism and springs changed a bit over their long production life.

A missing shim would create a light path deeper into the back. The spring for the shutter interlock (when the dark slide is in) pops out easily and likes to run and hide, so be careful when you open up the back. The shiny arm at the bottom is the interlock, and if it is missing, there is a light path into the dark-slide cavity. Does your back prevent the shutter button from being pressed if the dark slide is inserted - can't quite see if the interlock is there in your picture.

The spring bar at the top is the interlock to prevent the back from being removed when you have the dark slide out. It also like to fall out and get lost.

When the plate is off, you can straiten the tabs if you don't like how they are slightly bent.
 

Philippe-Georges

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There is one screw missing on the left side, as seen on that photo, left to the red arrow...
 

Arthurwg

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Wow. That is one very beat-up film back. Suggest you replace with a newer one. But meanwhile. I suggest covering the dark slide slot with black masking tape, even before winding on the loaded film or directly thereafter. You might want to tape up the bottom as well. Sorta makes the Hasselblad more like the much less expensive Holga, but what the heck. And BTW, if you look at some of Ansel's Hasselblad proof sheets you will see all kinds of light leaks, including those of his iconic "Moon over Half-Dome," which was cropped into a rectangle eliminating the leaks on the left of the frame. I somehow expected that Ansel would only have the most light-tight backs, but no.
 

eli griggs

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"One of the ways to narrow down the location of the light leak is to take the lens & dark slide off, lock the (secondary) shutter open, hold the camera up to your eye and look into the mirror box such that you block off extraneous light, and us a small bright flashlight around the film back - body interface to locate the leak.,"

A good tip every Hasselblad user should know.

This should be made into a sticky.

IMO.[/QUOTE]
 
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Ariston

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Philippe-Georges said:
There is one screw missing on the left side, as seen on that photo, left to the red arrow...
Click to expand...
It appears that way, but it has been changed to a non-original philips screw. It is darker and settles down further, so it is hard to see in my pic.

Just so everyone knows, the light is leaking between the body and the back on the bottom side, not from within the back itself. I have confirmed this with a flashlight in the dark. So, when the slide is not in, the light leaks between the back and the camera at the bottom, resulting in the "shadow" line cast on the film. I appreciate all the help. The bent tabs are keeping it from mounting flush. I'm not sure how the shims behind that would alter the relation of the plate to the camera. If I don't feel I can safely bend them back some, I will probably put a strip of electrical tape or something on the bottom part of the mounting plate.
 
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