Hasselblad A16 strange lines between frames on negs

[Filmandfile]

Hi, just got an a16 back and the frames all look fine and quite consistently spaced. However there’s these strange lines between each frame, anyone got any ideas why these are there?
Thanks
Ben

 

[Don_ih]

I think it's a thin light leak at the upper edge of the film holder. (I've seen them on some of my negatives.)

 

[Filmandfile]

I think it's a thin light leak at the upper edge of the film holder. (I've seen them on some of my negatives.)

As far as I understand there is no light seal at the top is there? Thanks Ben

 

[itsdoable]

This is what the film gate looks like (A12 instead of A16, but the same idea).

The rollers define the top and bottom of your frame, which is why the corners have that small hook. But light also leaks past the other side of the rollers (red arrows) on some film backs, which results in those thin lines you see between the frames.

It is usually less visible on the A12 as the film starts to arc away from the roller, but on the A16, the film remains relatively flat on the outside of the rollers.

You can check your film back by putting something bright/reflective (like the back side of the paper leader) and see if you can see the film on the other side of the rollers.

 

[RalphLambrecht]

View attachment 384132 Hi, just got an a16 back and the frames all look fine and quite consistently spaced. However there’s these strange lines between each frame, anyone got any ideas why these are there?
Thanks
Ben

clearly for Sirius Glass to answer!

 

[Don_ih]

As far as I understand there is no light seal at the top is there?

There is the seal at the dark slide, as everyone knows, and there is some other light seal material in the back that also degrades over time - and practically never gets replaced (you'd need to take the back completely apart.

See part marked 28, which is labelled as a light seal. I figure that's no good, anymore. so it lets in that tiny line of light.

 

[Dan Daniel]

One general procedure for finding a light leak- put the negative in the camera (or camera back in this case) as it would have been when it was exposed. Sometimes this will show you exactly where the leak is, or at least point you in the general direction. So itdoable's masks that could be the source might match your film?

I don't know much of anything about Hassy backs, but those little lines sure look like highlights as light bounces off of rollers.

 

[brian steinberger]

I have an A16 back I recently got from KEH. Mine produces the exact same lines. I’m not really worried about it. I assume this is normal.

 

[Ben Hutcherson]

I've seen it on several A12 backs also, but never seen it intrude into the image area so haven't worried about it.

I have also seen light traps that leak just at the edge.

If you suspect that's the issue, good quality replacements are ~$15 on Ebay and it's a 10 minute job to install them. I quite literally just ordered a dozen of them as I have a bunch of backs of unknown provenance and it's been ~5 years since I resealed any of the ones I have done(and several unknown backs failed the bright light test).

With that said, not saying this necessarily is the cause, but dark slides are considered a(somewhat) expendable item, and if replacing the light trap doesn't fix the issue it's worth trying a replacement darkslide. David Odess I think use to replace them on almost every back he serviced. They're pricey enough that I don't consider it a willy-nilly repair, but it's worth taking a close look at them. I have had at least one case where a back leaked nearly as badly week after replacement as before-I took it back apart thinking I'd somehow seated the replacement trap wrong, and found that a burr on the darkslide had gouged a nice slice through the new trap-the old trap was collapsed to the point where it barely interacted with that part of the slide, but the new one was torn all the way through the mylar after the darkslide had been in an out a dozen times.

 

[Don_ih]

It's not light leaking through the darkslide light trap. It's at the top or bottom of the back. There are light seals inside the back that decay just as much as the darkslide foam does but almost never gets replaced unless the back is sent for a proper service.

This light leak is insignificant and will probably never be a problem.

When the light trap for a darkslide fails, it spills light into the image frame.

 

[itsdoable]

It is not a light leak.

It is light that if focused onto the film plan from the lens. Inspect the detail in those slivers, you will see that they correspond to the continuation of your image top and bottom. There has to be a gap between the rollers and the film gate so they can spin freely.

 

[Don_ih]

It is light that if focused onto the film plan from the lens. Inspect the detail in those slivers, you will see that they correspond to the continuation of your image top and bottom. There has to be a gap between the rollers and the film gate so they can spin freely.

If that was the case, why would there be nothing between the image frame and the thin lines of exposure between the frames? Light isn't quite that cooperative.

 

[itsdoable]

If that was the case, why would there be nothing between the image frame and the thin lines of exposure between the frames? Light isn't quite that cooperative.

The roller (as pictured in post #4) blocks the light between the edge of the frame and the thin line...

 

[Don_ih]

Ah, now I see you're right. That's good, then. And what I said was the cause is actually impossible with a 645 back, since the line doesn't even come close to the outside of the back (it does correspond with the location of that roller, though).

 

[Sirius Glass]

clearly for Sirius Glass to answer!

I would have but I have never had that problem. I think that post 4 hit the cause of the problem.