Calumet 6 x 12 roll film back - linear fogging

Has anybody else had problems with regular vertical strips of fogging appearing on their negative when using the above slot in back? I’ve only used the back on 3 or 4 trips since I bought it and most (not all) films show these stripes. I can’t figure out whether it’s due to bright conditions, bad back closure, winding the film through without reinserting the slide (don’t do this all the time) or perhaps simply the same black magic juju that’s robbing me of my last frame on every film. If the thing wasn’t so costly I would probably have applied some hammer maintenance on the thing by now.

Any (helpful) comments would be appreciated before I send a rude letter to Calumet.

M

I've had the same problem with the 6x9 version of the same back. I traced it to my practice of fully removing the dark slide. Doing so provides an avenue for light to enter the back and fog the exposed film.

To prevent this, I only pull the dark slide out to the point at which it clears the film frame. On the 6x9 back, this point is indicated on the dark slide itself by a red line.

For added insurance, I also orient the film back so that the dark slide opening faces away from the light source and sometimes leave my dark cloth in place to shade the opening. All of these efforts have resulted in the elimination of the problem you've mentioned.

Just a related comment: My 6x9 Calumet RH came with a plastic slide which broke after awhile. When I ordered a new one and they sent a new treated steel one. I have never used it in bright sunlight, but in the studio with 10,000 watts of tungsten lights and having the metal slide pulled out all the way for approx 1 minute at a time, I've never had any leaks on EPY film.

Be sure you're not pulling the dark slide all the way out.

I own and regularly use 4 of the 6x9 backs. One for color negs. one for the bulk of the trans. brackets, one for "test" exposures that I run first at the lab and one to keep open if I need a special film. I buy one new one a year and retire the ugliest one. I shoot architecture in SW sunlight and have never had a problem completely withdrawing the dark slide. The only similar problem that I had was on one that I dropped. It acquired a crack in the case on the end where the darkslide inserts, above the rivets. This crack produced longitudinal fogging under certain conditions. I fixed it with a piece of gaffers tape.

The only real problem I have with them is that the mechanisms wear out relatively soon, about two years under heavy use.

I am using a shen hao 6x12 roll film back and I am also experiencing this very annoying vertical fogging about 1 cm into the picture on the 'dark slide insert side'. As have been stated before, one should not pull the slide all out, so I am not doing this. BUT I still get the fogging on some of the pictures.

Could there be a problem with the slide, which is blank metal, that it actually reflects light if it is not pulled out far enough from the picture, i.e. reflecting the light coming in from the lens? (In 6x12 format there are very small tolerances regarding not pulling the slide out and still having it in the hoolder)

Do I need to paint it black or choose to make a plastic slide?

Regarding film-flatness I, have not experienced any problems.

Thanks,
Patrik R

One addition regarding last slide juju...
Some people claim that for 6x12 you should start with frame 2 then wind up to 4 and so on. I have found this to be wrong!
I always start with the first slide starting with number 1, then 3 ,5 and so on. This leaves enough room for the last 6th picture not to move around due to slipping out of the roller.