Help diagnose leak in Hasselblad

Colden · Jan 28, 2010

Have a black late model 500 CM (KEH bargain grade) with a bargain old-looking A12 back.

The negatives have a black fogging spot expanding into the frame starting from the edge of the visible frame on the side of the dark slide, on the lower portion of the picture frame. The negatives are not fogged outside the visible area, neither the film edges nor the area outside of the mask.

The fogging is proportional to the time a particular frame spends in the camera, i.e. a frame will be fogged less if it is shot and advanced quickly and the fogging will be really apparent if the frame is left to sit with the dark slide out for several minutes.

My theory is that light enters through the hole once the dark slide is removed. I suspect the problem is the A12 back and not the body, but I have no experience with Hasselblad problems, so I need some help. Should I just get a different back and try again, or is there something else that I can do?

I was going to use electrical tape on the dark slide opening but don't want to pay for more processing until I get some pointers.

Thanks a million.

mpirie · Jan 28, 2010

Hi, this sounds like the perennial light seal problem, but posting a scan might help diagnosis.

There's a flexible mylar and foam light seal where the darkslide enters the back. It wears and needs to be replaced at regular periods, especially if the back hasn't been used for a while as the foam loses some flexibility.

Last time I did mine, they cost about $15 each and too all of 5 minutes with a small screwdriver to replace.

Mike

Q.G. · Jan 28, 2010

This page shows how to change the seal yourself, and examples of a light leak caused by a faulty seal (the shape of the fogging varies, depending on where the leak is exactly).

Sirius Glass · Jan 28, 2010

Get some light seals and install them yourself or ship the back(s) off for light seal replacements.

It is not hard to replace light seals.

Steve

jvan01 · Jan 28, 2010

You can test whether it's the fault of the light trap on the side of the dark slide.

After loading a new roll, get some black gaffer's tape and tape up the side of the darkside insert (with the darkside out). Shoot and see if the problem persists.

RalphLambrecht · Jan 28, 2010

Colden said:
Have a black late model 500 CM (KEH bargain grade) with a bargain old-looking A12 back.

The negatives have a black fogging spot expanding into the frame starting from the edge of the visible frame on the side of the dark slide, on the lower portion of the picture frame. The negatives are not fogged outside the visible area, neither the film edges nor the area outside of the mask.

The fogging is proportional to the time a particular frame spends in the camera, i.e. a frame will be fogged less if it is shot and advanced quickly and the fogging will be really apparent if the frame is left to sit with the dark slide out for several minutes.

My theory is that light enters through the hole once the dark slide is removed. I suspect the problem is the A12 back and not the body, but I have no experience with Hasselblad problems, so I need some help. Should I just get a different back and try again, or is there something else that I can do?

I was going to use electrical tape on the dark slide opening but don't want to pay for more processing until I get some pointers.

Thanks a million.

Here is an easy way to check for light leaks without ever taking a picture:

Get a miniature flash light and place it into the empty film back. Turn off the lights, let your eyes adapt to the dark for 20 minutes and inspect the back for light leaks from all angles.

I have not tried this with a Hasselblad, but it works well with view cameras.

Tobster · Jan 28, 2010

Another method I have used: Attach the empty film back on the body with the lens off. Take out the dark slide and peek through the lens opening while shining a flash light into the slot for the dark slide. If you can see any light inside the body, the light seal in the back is defective.

This is a very common problem, I have replaced the light seal in all my three A12 backs.

John Koehrer · Jan 28, 2010

The light seals you need are not the rubber ones but genuine Hasselblad type seals. They're much like a plastic weatherstrip door seal, a V shaped plastic.

Q.G. · Jan 28, 2010

So that it is clear: the part that needs replacing is the 'rubber' foam. It deteriorates with time, crumbling away, and changing from a thick springy foam to a thin sticky goo.

The foil that the foam is placed on/in only needs replacing when it is physically damaged (torn).

The foam is the working bit of the seal. It shapes itself around the slide, and springs up to fill the gap when the slide is withdrawn.
The foil only serves to protect the foam from the sharp edge of the dark slide.

If you get a new foil with a seal kit, keep the new foil until you need it.
What i do is cut my own foam strips from a cheap foam mat bought in a crafts store. The sheet i bought (about A4 in size) did cost about (i forgot the exact sum) $ 2 or 3, and will provide probably close to 100 foam pads. Works perfectly.
Finding a cheap replacement for the foil is another matter. Someone suggested an exposed and developed leader of a roll of 35 mm B&W film. I'm not quite happy with that. Too stiff.

So yes, it is the rubber foam that needs to be replaced.

Colden · Jan 28, 2010

Thank you for your very competent replies.

It was immensely helpful and I appreciate your time.

Tobster · Jan 29, 2010

Q.G. said:
Finding a cheap replacement for the foil is another matter. Someone suggested an exposed and developed leader of a roll of 35 mm B&W film. I'm not quite happy with that. Too stiff.

I ended up making one out of a piece of processed 120 E6 film. I am not sure if this is the best solution, but it has worked without problems so far.

brucemuir · Jan 30, 2010

I've so far bought the 12 dollar kits but would like to explore making my own from now on.

What thickness of foam would be recommended.

Q.G. · Jan 31, 2010

I use a 2 mm thick black foam.

The original foams are backed with a concave-convex plastic strip ('aluminized' on one side) that acts as a spring, pushing the foam up.
The replacement foam i use is denser, i.e. harder to compress, and works absolutely fine without such a spring.

The stuff being as cheap as it is, i change seals more often now.
Too often, perhaps, since i have yet to find out how long these replacement foams really last.

RalphLambrecht · Jan 31, 2010

Q.G. said:
I use a 2 mm thick black foam.

The original foams are backed with a concave-convex plastic strip ('aluminized' on one side) that acts as a spring, pushing the foam up.
The replacement foam i use is denser, i.e. harder to compress, and works absolutely fine without such a spring.

The stuff being as cheap as it is, i change seals more often now.
Too often, perhaps, since i have yet to find out how long these replacement foams really last.

Q.G.

If you haven't done so already, can you share the source for this foam?

Q.G. · Jan 31, 2010

I get mine from a local hobby/crafts store. It's stuff people do all sorts of things with.
The German name for the stuff is "Moosgummi", i believe a brand name for it is "Crepla".
Incredibly cheap: € 0.90, i.e. $ 1.25, for an A4 sheet.

brucemuir · Jan 31, 2010

I've seen all kinds of material used.
One back I opened had this pink felt in there.

In the US I would think "Michael's" craft joint or one of those type chains. I got some thinker stuff there to seal my enlarger head.

John Koehrer · Jan 31, 2010

brucemuir said:
I've seen all kinds of material used.
One back I opened had this pink felt in there.

In the US I would think "Michael's" craft joint or one of those type chains. I got some thinker stuff there to seal my enlarger head.

Maybe you're over thinking the solution.

brucemuir · Jan 31, 2010

haha,
My MBP keyboard needs replacing or maybe my skills are hurtin'

buranlad · Feb 2, 2010

Hi all,

I am new here... first post.

I have searched and searched for my problem, but to no avail.

If you don't mind, may I piggyback on this thread with a light leak query as this is the most recent thread on topic?

MattKing · Feb 2, 2010

buranlad:

Welcome to APUG!

Piggybacking is fine, but you should also feel free to start your own thread.

You can always link back to this thread in your thread.

Matt

fotch · Feb 2, 2010

Hey buranlad, welcome aboard.

buranlad · Feb 2, 2010

Hey!

Thanks for the welcome.

I have a leak that you might find interesting as it is rather unusual (meaning of all the "LL" images I have looked at, I have not seen one quite like it).
It appears to be perhaps a mechanical issue (as though the back was not completely engaged with the body) rather than classic "LL" rays.
It looks as though the light was penetrating near the gear engagement between the body and back.
But... the body/back performed fine... meaning that there were no hints of an issue until processing.

Is it possible this happened during handling/processing of the film?

The gear was a 553ELX and E24 back, both in excellent, serviced shape. The film was 220 Kodak 160VC Portra. The "LL" was through the entire roll.
Below is a link to an "average" example from the roll. Some frames were much worse, some a lot better.

http://www.flickr.com/photos/28347796@N07/4319490098/

Thanks in advance for any thoughts/insights!

Q.G. · Feb 2, 2010

That looks like it must have happended during processing, yes. Or rather, during handling of the film before processing.
Not a leaky back.

By the way: the image is upside down and left right reversed in the back. So the leaks are not on the side of the mechanical interface of camera's and back's mechanisms. But that doesn't say much really: light can leak in on one side, and hit the film on the other side (as typical dark slide slot seal leaks show).

Can you show the frames that are affected worst?

buranlad · Feb 2, 2010

All,

First, @Q.G. I have read a million of your posts here and elsewhere, a pleasure to "emeet" you finally!

OK... I have uploaded two more frames... the worst and the best from the roll.

While going through the frames, especially the worst one... it seems more evident that this was indeed a handling issue. So much so, that I feel stupid now for thinking otherwise!
I would, of course, love to hear what everyone thinks!

They should be accessible from the same link I previously provided... then click on my "photostream" -they will be titled Worst and Best respectively.

Thanks again!

buranlad · Feb 3, 2010

My developer just emailed... found a fault with the changing bag used! It has been "retired!"

Thanks everyone.

Help diagnose leak in Hasselblad

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