B&W Film... What caused this?

Discussion in 'Film and Processing' started by sebastianmoran, Nov 3, 2010.

  1. This just back from a pretty good lab, machine processing, of 120 film, 6x9, Mamiya Press, known good lens, this is the third frame on the roll, adjacent frames are OK.
    What caused the un-evenness? The right-half of the negative is thinner, and there is a vertical strip on the left that's thinner. (Thinner on negative = darker on scan.) Both are visible on the negative, so it's not just a scan artifact.
    Any ideas what caused this? Exposure? Or processing? Is this a glitch in the machine processor? It is as though the first 2 1/2 frames are under-developed. I can't imagine that something in front of the lens has caused this.
    120 Film, 6x9 -- What caused darker areas (right half frame, vertical strip near left edge)
  2. Here's frame #2 from the same roll, tone is consistent from left to right. Above is frame #3 with the problem.
    This is preceeding frame from the same roll.
  3. Looks like a shutter problem with the camera, not moving at the same rate thorough out the exposure.
    Which shutter does the camera have a focal plane or leaf in the lens?
  4. Yeah, I know it looks that way. But, it's a leaf shutter, in the lens, so I doubt it's the shutter.
  5. If these are full frame images, then the 6 cm dimension is vertical. Therefore these images were traveling horizontally through the processing machine. I know lots of ways to get uneven development with streaks running along the length of the film, but not across the width of the film. That would suggest a camera problem, but if I recall correctly, this camera has a leaf shutter.
    Could this be light fog from film that was not tightly wound after exposure? Look at the unexposed edge of the film. Is it uneven as well? That would suggest light fog.
  6. Possibly a glitch in a roller processing machine. I had a roll like this years ago and the lab operator apologized profusely. Apparently a breaker tripped and the film just sat for about 45 seconds while they located the breaker. The darker part of the print is where the film sat just out of the developer.
  7. The problem frame is frame #3. So I doubt film winding. Also, the unevenness is entirely in the frame; film edges seem perfectly clear.
    Ron, yes, these are full frame. Yes, the film is traveling horizontally through the processor.
    If the processor stopped briefly, there would be an area of more development = denser negative = lighter area of image.
    Looking at the whole strip of film, it's as through the first 2 1/2 frames had less development, or that at least a 1 1/2" portion of frame 3 had more development (maybe the whole rest of the roll had more development, can't tell). Is there a speed switch on these machines? To select development time? If someone bumped the switch mid-roll, that would account for what I see. But, this is all guessing.
  8. Looks like some form of uneven development? Though I've no idea why it should affect only one frame!
    Other than that, could it be an emulsion fault (very unlikely with modern QC in film manufacture, I know). If it's an Ilford film, they are very helpful in advising on problems with their products, and no doubt Kodak would also advise.
  9. Frame #2 has the same flaw as frame #3 but it is not as pronounced. The left 60% looks normal while the right 40% has a 1/3 or so more exposure or more development.
    With the aperture wide open fire the shutter on 1 second and observe the shutter blades. All blades should move evenly thorough out the complete cycle.
    Position the shutter so that you can see the shutter blades and the second hand on a watch or a clock at the same time. Set the speed to 1 second. Cock the shutter, trip the shutter just as the second hand reaches a second mark. The shutter should fully open and just close as the second hand reaches the next second mark. Any variation more than the width of the second hand is unacceptable and the shutter needs servicing.
    A processing error will not cause the same flaw over a partial frame for several frames varying only in severity and not affecting the edges of the film. A light leak or seating problem might be the cause but the film edge and or focus would also be affected.
  10. Thanks everyone for the suggestions.
    Charles, I think there's gradual darkening of the sky on the right in both frames, and this comes from a polarizer. I will check the shutter. I have six shots in this location, three B&W, three on Ektar 100, and only one shows the pronounced density change.
    I just talked to the lab; the processor is a "dip and dunk" machine, not a roller processor. The result is not consistent with a stopped machine. This is still a mystery.
    Could I possibly have had something in front of the lens to produce this result?
  11. Do you have a strap on your camera? Could it have drifted in front of the lens for a fraction of a second?
  12. A strap or other non optical object in front of and close to the lens will leave a slight soft focus outline of that object on the negative the same as it was when the image was exposed.
    A polarizer may have caused the effect but I am not that familiar with possible errors that can occur with their use.
    I have had a few shutters that were obviously slow on first fire after sitting overnight then would fire near correct until allowed to rest for several hours. Exposure errors with shutters like this are usually even across the frame.
  13. James, good idea. No strap. Charles, thanks for the latest comment. Still a mystery, what would affect this part of this frame only.
    I have been trying to figure out if I could have gotten my hand or the darkslide in front of the lens for part of the exposure. A bird?
    FWIW, the shot was 1/60th at f/22 with polarizer, according to my notes. And, I have a DSLR capture at the same time, with polarizer, that looks just like the second image.
    Sounds like no one has seen this kind of thing from a leaf-shutter camera.
  14. Thanks all... I'm going to summarize and then leave it for the archives.
    • Inspecting the negatives, the right half of #3 looks comparable to other frames on the roll, so the defect is the area which is lighter in positive image, denser in negative
    • defect is in the negative, not a scan artifact
    • defect is on frame #3, not on other frames on the roll, not at beginning or end of the roll
    • defect is in one frame of one roll, not on other rolls exposed at the same time with this lens/body.
    • defect is uniform from top to bottom of the exposed frame; that is, across the 6cm width of the 120 film
    • defect is in the frame area, not on the film edges outside the frame
    • defect is within the frame, not at the left or right edges of the frame
    • defect starts 10% in from left edge and runs to 60% across the image, total width of defect is 50% of the 6x9 image. Defect does not touch left edge of frame, and does not get anywhere near the right edge of frame.
    • shutter uneven (but it's a leaf shutter)
    • processing fault (e.g. machine stopped or slowed)
    • film manufacture, uneven coating (unlikely)
    • something momentarily in front of the lens (strap, hand, bird)
    • polarizer accounts for gradual darkening of sky at right, but not for the defect
    Base data:
    • 120 TMAX 400 in a Mamiya Universal Press, 6x9, full frame shown
    • Late afternoon, good light, polarizer, 1/30 @ f/22
    • Dip and Dunk machine processor at a good lab
    • Lab scan, unadjusted except for size
  15. Having used a Hasselblad years ago, a slight-bend in the magazine slide would cause some odd things with the film. Did, by chance, you put the darkslide in-and-out with the frame that is damaged? If not, the film developer *somehow* was working on that one frame longer, causing the un-even results.
  16. James G. Dainis

    James G. Dainis Moderator

    Comparing the two photos above, it seems that in the bad photo, the right side is properly exposed but it is the left side that is lighter, overexposed, or given more development. That would eliminate any problems with the dark slide or something blocking the lens. No exposure of the frame edges would also eliminate a light leak from the back or during film handling. The extra light came from the front or from over development of the left section of the frame. A problem with the leaf shutter shouldn't cause this unless part of it partially hung open. I would think that a light leak around the lens or the front of the camera would cause more burning that the light amount that is shown here. That leaves me with the conclusion that it was something in the development that caused over development. What exactly, I can't say.

    The only other thing that I can think of is, a bright light source reflected onto one half the polarizer filter, lightening it and causing the problem.
  17. The sharpness of the defect makes me want to look harder at the back and dark slide area. Perhaps the seating of the back. Anything in front of the lens would not be that sharp. If dip an dunk I doubt it's in processing. A light leak outside the back would show on the rebate edge but not if it happened inside the back. A stuck aperture blade would not appear so linear. That appears to be the edge of a dark slide. Why on one and not the other frames I can't say.
  18. Jerry, James, thanks for the comments. Yes, I put the dark slide in and out on each exposure.
    Louis, your thought suggests one additional hypothesis: The shutter isn't closing fully. The camera was on tripod. Perhaps I had the dark slide halfway in for a while, overexposing the left half. On this camera, the right half of the image would be protected and the left half would be over exposed, consistent with the observed defect, except that the left-most 10% looks OK.
    That's easy to test and I'll do it. I'll expose a Polaroid, then leave the darkslide halfway out for an hour.
  19. Louis, that was an interesting idea, but it's not the source. I exposed the Polaroid, then left the dark slide half-way out for a couple of hours. No sign of any problem.
  20. Sebastian, I think you could be dealing with a random fog from static electricity. Those dots in the sky you see where the density is correct look like static electricity fog, and they extend into the fogged area.
    Before exposure - It could happen in the camera as the film was advanced. A temporary static charge that was built up in the camera that discharged.
    After exposure - It can inadvertently happen when the person processing it is separating the film from the backing paper.
  21. Thanks, Keith... I'm much more worried about the gross density difference between the left-hand side and the right-hand side of the frame.

Share This Page