Marks on negatives - what is causing them?

I am getting occasional marks appearing on 120 Tri-x negatives taken with a Rolleiflex. The marks are faint bars appearing at the bottom of images. The mark does not appear on all images; maybe one mark per film and does not necessarily appear on the same exposure number on the next film. When the problem does occur, the marks always appear at the bottom of the image. This is not a scanning problem as the mark appears on the negatives.

Does anyone know what is causing these marks?

I'd check the light seals around the camera back. Especially around the film supply compartment, which is where you could get a slightly fogged section of film before it moves up behind the lens.

I noticed that on my Rollei Automat. I noticed little teeth marks on the edge of my film. I don't know if it's the same issue. I think it's caused by the gears for the film counter that's touching the film. That's my best guess.

Looks as if the bottom edge is slightly underdeveloped, how much developer are you putting in the tank, I used to get this with 120 film when I only used 500 ml in my tanks, I think sometimes the reel slightly slides up the center colum, causing the top edge to be sitting slightly above the dev, I now always put an extra 50 to 100 ml of developer in the tank and have not had this problem since

A couple of years ago, or so, an APUG Rollei user documented a somewhat similar problem of increased density along one edge on some frames. It turned out to be reflections off one of the guide rollers which would catch light if there was a bright highlight in the frame in just the right place.

bdial said:

A couple of years ago, or so, an APUG Rollei user documented a somewhat similar problem of increased density along one edge on some frames. It turned out to be reflections off one of the guide rollers which would catch light if there was a bright highlight in the frame in just the right place.

Click to expand...

This would be my guess also since it is only happening on one or so frames a roll. Something like the sun in one edge of the frame would do it.

Might be what they suggest about the light reflections, I don't know, but if you hold the camera like I do, it's at the top of the neg (bottom of the positive, right?) Also, the area at the bottom of the positive image you posted is lighter than the rest of the image, suggesting additional, not under exposure/development, whichever it is. I don't think it's a development issue, since, again, if you hold the camera like I do, the edge that would suffer from inadequate amount of developer would be along one side or the other, not between images, and would not have such a straight clean edge.
I use 2 rollei's and have never seen this.
Two questions come to mind:
Does it happen on every roll somewhere?
When it happends, is there always a bright area in the frame, with low shadows where the offending area happens? The second of your images could have bright sky area that you cropped out for the image posted.

That would be the famous Rollei roller reflection. When light comes through the lens and hits the film there is some bounce of the light. There is a slight gap left between the film and the film gate made because the film track is slightly higher than the film gate. Otherwise you would get scratches on your film. The light bounces through that gap and hits the chrome roller at the bottom of the film gate. If there is enough light it will cause a plus density stripe across the width of the film. Remember the image is upside down inside the camera. That means that the light spill comes from the top of the previous frame and spreads into the bottom of the next frame. It is most noticeable after the 12th frame in the blank follow leader. Some cameras seem to get it worse than others. It might have to do with some internal flare from a slightly hazy lens or it might just be that one camera has a shinier bottom roller than another. To fix the problem in the newer Rolleis they have changed the rollers to black and tried to close the gap a tiny bit. However I can attest that even in a new FX, which I have, there is still some roller reflection. With the black roller however it is less than half the density. If a camera has perfect spacing the density bar falls almost right at the edge of the next frame so you don't see it. Some cameras have a very bad case of it and especially if you tend to take pictures with sky at the top. I have heard that the 3.5 cameras have it a little less but I personally doubt it.

Dennis