another rb67 back problem

[nwilkins]

I have two RB67 Pro S backs, and one of them is working fine. The other is producing a thin line on the film (across the bottom of the frame in landscape orientation, or left side in portrait). Has anyone ever seen this phenomenon before? It almost looks like a scanner artifact, but it is clearly present on the negatives themselves (and does not appear on films from the other back). Here is a crop of an image where it is noticeable:



Any ideas what is happening? Is something scratching the film?

 

[MattKing]

Has the image you posted been inverted to a positive, or are we looking at the negative itself?

 

[nwilkins]

no that is inverted to a positive. so in reality the line is clear on the negative. basically looks like a line where there is either no emulsion (a scratch?), or where the emulsion was not exposed to light (which seems unlikely, no?)

 

[polyglot]

Look for something scratching the film, e.g. where the insert plugs into the frame of the back.

 

[nwilkins]

yes I shall do once I finish off the roll that is in there. This is the same back that has been having the trouble with the counter - thinking it might be time to look for a new one anyway.

 

[Alan Klein]

I once had one of my wife's red hairs trapped across the film opening leaving a thin red line across every negative.

It better not be one of hers!

 

[MattKing]

no that is inverted to a positive. so in reality the line is clear on the negative. basically looks like a line where there is either no emulsion (a scratch?), or where the emulsion was not exposed to light (which seems unlikely, no?)

Sounds like something is intruding into the edge of the film gate, and therefore blocking the light.

Is there a problem with the film gate, such as a loose piece of film from the dark slide channel?

Is the back not mounting correctly to the rotating adapter?

 

[nwilkins]

thanks for the suggestions - I will look into these possibilities. it feels to me like scratching is the likely cause. If something is blocking the light it would have to be a very thin hair or thread, and this is unlikely since looking back the problem has been occurring for at least the last 10-20 rolls. I just haven't noticed it because it is virtually hidden unless the negative is very dense along that side, and also I usually crop to 4x5 so I don't pay much attention to the very edges of the long sides of the neg.

 

[snegron]

I had a similar issues with one of my backs. It also leaked light. I noticed that the foam was gummy and and some particles got caught in the track. You might want to get that back re-foamed/cleaned/repaired or you might risk ruining more film.