strange film fog problemgreenspun.com : LUSENET : Large format photography : One Thread
Hello, I experienced a strange film fog problem on my last exposures. I exposed an 8x10 neg. hp5+ in early morning light. Sun was at my back and up at about a 20 angle. I used my 300mm lens and a 21 orange filter in a Calumet gel holer clipped on the lens with barn door type shade. When I processed the film I got a one inch strip that ran across the entire neg on one edge as though I was making a test strip on paper( did not go to edges of film). I though at first it was a processing problem (PMK) So next morning I went back and made two exposures with a diffent holder same light conditions. Processed one neg. in PMK and one in hc110 and I got the same one inch strip on both negs. I then checked my camera all over for any leaks none found. I have since made other exposures with no problems. My only though is that I had some kind of internal reflection of light. What about this type of filter holder reflecting light back into the lens? anyone had any problems of this type? Thanks Bill Bartels
-- Bill Bartels (email@example.com), July 12, 2000
I got that on a couple of 4x5 negs too. 1/2" running lenghthwize -- had to crop it out. Did everthing normal too. I don't know what it is, but if it helps, you're not alone.
-- Dean Lastoria (firstname.lastname@example.org), July 12, 2000.
Have you checked your film holders for leaks? Maybe these particular holder didn't sit correctly? I had this problem, it was a light leak in the bellows right at the edge where it connected to the back standard. Bloody annoying and ruined some nice pictures. Took me a long time to track down the leak because it would only appear when I used rise on the back standard. I assume you extended the bellows to the full when you were checking them. At the risk of stating the obvious, maybe you were in a hurry and didn't seat the holder properly. I've heard that sometimes a bright object like the sun that is just outside the angle of view can sometimes bounce off a poor bellows but thankfully this voodoo hasn't hit me - yet. What about your loading area? Any chance that the gremlins were loose in the darkroom that night? I fogged some film once in a changing bag by wearing my bright luminiscent-dial watch. DJ
-- N Dhananjay (email@example.com), July 13, 2000.
What you most likely have is bellows interference on the negative. I have run into it on a few shots. One camera body is worse than the others, especially with longer bellows draw. Seems the bellows bows in a bit on that body when it stretches out. Another body does this on horizontals, on the left side. On this one the back bellows attachment comes into the edge a bit. Lens movement has more of an effect with this one. At times in the past I have run into it when using very wide lenses and picking up part of the front focus track. Check carefully & see which lens & bellows combination this happens with & you may be able to head it off when it would happen again. When working with very large view cameras with long bellows draw you need to be very aware of it. The bigger the format the more likely it is to show up if you don't set the bellows extension carefully (like using the little tabs onthe top to pull the bellows forward so the lens circle doesn't get cut off). A quick fix may be as simple as putting your hat under the bellows to keep sag from interfering.
-- Dan Smith (firstname.lastname@example.org), July 13, 2000.
Bill: I have has similar problems with a gel holder where there was a gap between the lens and filter. I got streaking and an image of trees behind me that were reflected through the lens. I solved the problem by draping my dark cloth over the camera and front standard, letting it hang above the lens. I would also check for bellows leaks. You shouldn't have more than normal extension of the bellows with a 300mm lens since that is the normal for 8x10, so extreme extension should not be the source of the problem unless you are doing closeups. I would check the back carefully for seating of back and holder since the sun was behind you. If you can easily duplicate the conditions, try draping your dark cloth over the camera back and making an exposure. Then make another with the dark cloth draped over the front of the camera and shading the lens. See if either of those shots are streaked. It should show where the area of the camera the streak is coming from. If neither neg is normal, the problem is internal with the bellows. Hope this helps.
-- Doug Paramore (email@example.com), July 13, 2000.
If the bellows were sagging in the way, the strip would be completely clear, not "fogged."
What is the extent of the fogging? Can you see your desired image through the fog, or is it completely black?
-- John H. Henderson (firstname.lastname@example.org), July 13, 2000.
Bill, I have experienced strange fogging on some exposures while using Cokin filters and holders using a medium format camera last summer at the Grand Canyon. It didn't appear on the entire roll but only two frames. I believe it was due to relection on the reverse side of the filter. There is a gap between the filter and the lens and the sunlight was reflecting through the gap. If there are no light leaks with your bellows and/or film holders I would try an exposure under the same conditions with the filter and one without to see if the back reflection is the cause. Good luck.
-- Pat Kearns (email@example.com), July 13, 2000.
Thanks to everyone for your input. I did get an image in the one inch strip it was just about 1 stop more exposed. I will try your suggestions when shooting in these conditons again.I have checked for light leaks very carefully. I use a high intensity fiber optic flashlight light that works very well and shows any leaks clearly.I don't believe it was bellows sag because it was a horizontal shot and the stip ran vertically the bellows extension was maybe 14 inches. Thanks Bill Bartels
-- Bill Bartels (firstname.lastname@example.org), July 13, 2000.