Scratches on film

[Christopher Walrath]

Next thing I would check as it is progressive would be tension on the film. As the diameter of the source spool gets smaller there is more angular tension on the first roller perhaps? Just throwing stuff out there now. As it is the same on every roll it has to be something on camera and the tensioner is the only thing I can think of that would change as the film use progesses.

 

[Tony-S]

What is the tensioner and how does one adjust it?

 

[Tony-S]

I just checked a couple of rolls of Fujichrome that I shot about two months ago and neither of them have scratches on any of the frames. Strange.

 

[Christopher Walrath]

Did some more searching.

Cinch Marks - Not to be confused with sync marks. Cinch marks are small vertical scratches on a roll of film that are caused when the end of the film is pulled to tighten the roll, causing any dust on the film to make a small scratch. Too much drag on the supply while rewinding is one common way that cinching can occur.

Perhaps the winding spool is not releasing properly. I don't know. This is out of my league.

 

[Tony-S]

Ok, I'll pursue that more. Thanks for you help on this. I'd hate only get 7 frames a roll, if you know what I mean.

 

[Christopher Walrath]

I gotcha. I just hope I helped.

 

[MattKing]

Thinking aloud about this ....

As you expose the roll, the film rolls off the feed spool, past the "gate" and on to the take-up spool.

As you work through the roll, the geometry will change slightly, because the thickness of the film on the feed side will decrease, and the thickness of the film on the take-up side will increase.

It would seem that something is causing pressure or scratching near the end of the roll, but not near the beginning.

Can you put a throwaway film into the camera, and then open the back after 8 shots are advanced, to check for obstruction of some sort?

Could it be a problem with the frame counter mechanism? An introduction of some friction when the counter reaches 7?

Matt

 

[Tony-S]

If it would help solve the problem I would do it. What would I look for? Or is it one of those things you'd just have to see?

 

[MattKing]

If it would help solve the problem I would do it. What would I look for? Or is it one of those things you'd just have to see?

I'd look for some evidence of something barely intruding on the film path, or a roller that is only really engaged when the film nears its end, or some indication that the film counter connection is acting up.

It would be a good idea to compare it with the setup when the film isn't loaded.

It is my guess that the problem is with one of the rollers.

Is there any chance you could borrow another insert or back to try it out?

Matt

 

[Christopher Walrath]

Another question might be where the cinch marks are occurring? When looking at the negative as it would be oriented in the camera (neg upside down and emulsion facing forward), where are the scratches? That would also tell you where the problem might be.

 

[Tony-S]

Keep you fingers crossed: I think I found the problem. I had been scrutinizing the two rollers of the back and the film insert. What I missed was the back's lip on the receiving roll side. Running a finger over it I felt a couple of bumps along the way. I've taken emory cloth to them and they're gone now. I'm going to shoot and process a roll tonight or tomorrow. Hopefully this is it.

 

[Tony-S]

No dice. That did nothing. This is quite frustrating and depressing...

 

[Tony-S]

OK, new update. I picked up a 220 back and insert, and put the 120 insert in the 220 back (the backs appear to be identical). I loaded a roll of Delta 100 and shot 9 frames and left the 10th frame unexposed. In the darkroom I removed the film from the back without spooling it onto the uptake reel (i.e., frame 9 was still on the film platen and frame 10 was still on the source reel) and then processed as normal. The idea here was *if* there were scratches on the frames I could then localize the source of the scratches.

None of the frames had scratches on them. This seems to suggest that the problem lies with the original back, right? It cannot be the 120 insert, otherwise I would have had scratches on the film.

So my next plan is to use the 120 insert with the original back again, which should produce scratches on the film. Again, I will only shoot up to and including frame 9, leaving frame 10 unexposed, then pull the film from the back without spooling it onto the uptake reel. Process and I should see scratches. These are the two possible outcomes:

1. If they are on frame 8 and the left side of frame 9 (i.e., the frame 8 side), then the culprit is the source roller of the back.

2. If there are scratches all the way across frame 9 and onto frame 10 (unexposed) then that means it must be the uptake roller of the back.

Does anyone see a problem with this rationale?

 

[MattKing]

Tony:

If I were you, first I would shoot a full 120 roll with the 120 insert in the new back and wind it through normally to the end.

That way, if you get a result without any scratches, you will know that the problem is with the original back and, more importantly, you can avoid the problem entirely using the 120 insert in the new back.

If, however, there are scratches this time as well, you will know that the insert plays a roll as well.

Matt

 

[Tony-S]

Good point. I will do that first. Thanks.

 

[Tony-S]

If I were you, first I would shoot a full 120 roll with the 120 insert in the new back and wind it through normally to the end.

With the 120 insert and the new back, the scratches are gone. Clearly there is an issue with the original back. Now I need to isolate it to one side or the other. As far as I can tell, there are only two contact points on the back - the rollers on the source side and uptake side. One more roll ought to get it to one of these rollers. I'll use the plan described above - shooting frame 9, then pulling the film out in the darkroom without advancing it any further. Any other comments before proceeding?

 

[Tony-S]

OK, more weirdness. I put the 220 insert into the back that came with the 120 insert and which was causing scratches. I shot a roll of Fuji Velvia 220 and there are no scratches at all. Any ideas what may have happened? No paper on 220 film, perhaps that was the problem before?

At any rate, my problem is solved just by switching the backs and inserts.

 

[Christopher Walrath]

Wirelessly posted (BBBold: BlackBerry9000/4.6.0.297 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102 UP.Link/6.3.0.0.0)

So let us get this straight. This only happens on which backs and with which inserts?

 

[Tony-S]

With the 120 insert and the back it came with. I bought a 220 insert and back, switch inserts and now no scratches on either 120 film or 220 film.