If the spots (more of a line in the example shown) are the result of bird flight paths, then the birds must have been darker colored than the surrounding sky (unless they were in silhouette). This is possible, but is something that you should have noticed just before shooting. If this is the case, you need only wait for a lull in the action and then shoot without the bird blurs.
I did some spotting on a 16” x 20” print from 4” x 5” T-Max 100 negative last night. It’s an early morning view of trees, beach, and marsh grass looking out across Lake Erie towards the distant shore of Ontario.
The negative has a single small defect in the sky area similar to what you showed. It prints as a slightly curved line of moderately greater density than the sky. If it were lighter than the sky it would be easy to spot dye it to match the surrounding area.
The edges are somewhat fuzzy. It’s not black and that means that the image of the line on film is not transparent, just lower density than the surrounding area. It was most definitely not a bird as I made sure that no birds were flying across the scene before shooting.
It’s just enough to be annoying on close inspection. If it was over a darker element, it wouldn’t be noticeable.
On the print, the line is about 4.5mm long and 0.3mm in width. I’m nearly certain that it was caused by the shadow of a micro fiber that had clung to the film during exposure. The magnification of the projection was about 4.7X, so the image of the line on film is about 0.97mm long and 0.06mm in width (or 0.0025” wide x 0.038” long).
No matter how careful we are, sometimes particles of various types stick to sheet films or the holders, or dark slides. There’s no escaping handling sheet films. Particle contamination can be minimized by careful housekeeping in the film loading area and cleaning of the holders. Unfortunately, we can’t totally eliminate the problem.
We all know from observing a shaft of sunlight in a darker room, even one that is scrupulously clean, that there are always visible particles floating in the air. These can adhere to films and cast their shadows during exposure.
I have seen these artifacts on my sheet film negatives occasionally and compared their size and shape to the fibers mentioned in post #5. They seem to match.
One trick that I’d read about years ago might help. Some folks run a room vaporizer for a few minutes in the film loading area to settle dust and help eliminate the static charge that draws particles to the film.
I’ve though of, but not tried, the idea of using a grounding strap that fastens around the wrist with a conducting wire clipped to a bare metal water faucet or the metal case of an electrical outlet to ground us while we load sheet film into holders.
The idea is that any static charge we generate through friction: tearing open a sheet film packet, sliding the films out of the packet, sliding the films into the holder, etc. are discharged to ground so that no attractive charge forms in the first place. Such grounding straps are ready made and inexpensive. They can be bought at Radio Shack or other electronic supplies stores.
We might also place the holders on an aluminum cookie-baking sheet with a length of copper wire and a couple of alligator clips to connect the sheet to a convenient source of ground. Whether these steps help can only be determined by trying them.
I’m not aware of any film manufacturing errors or processing errors that would cause these marks on films. That these occur almost exclusively with sheet films and not roll films lends credence to their being caused by very small fibers sticking to the emulsion during exposure.
This can happen to a roll film, but only rarely. If the film chamber of a roll film camera is allowed to get contaminated with dust and particles, some of them can find their way to the film and cast shadows during exposure. But a roll film camera whose film chamber is brushed and blown out regularly rarely accumulates particles to cause the problem.
Last edited by Ian C; 10-03-2011 at 12:34 PM. Click to view previous post history.
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