Page 1 of 2 12 LastLast
Results 1 to 10 of 19

Thread: Unexpected 'optical spots' on film

  1. #1

    Join Date
    Dec 2012
    Location
    Superior, WI
    Posts
    22

    Unexpected 'optical spots' on film

    I have taken 5x7 Ektachromes since 1971, same with K B Canham 5x7 wooden view camera since 1999. Starting 8-12-2012 I got my first 'optical spot' on my film. Such spot looks like a pinhole image of the sun. Its properties are the following:

    -1- shows up once every 5 or 10 Ektachromes
    -2- only with sun shining on sunlit scenes
    -3- sun can be in random direction
    -4- spots always round, always the same size
    -5- spots can be a differing positions, often near the edge of the film but not always
    -6- independent of which film holder (I have 5 each Lisco holders bought year 2000)
    -7- independent of lens 72 mm up to 450 mm
    -8- independent of bellows extension
    -9- independent of bellows (I just purchased a new Canham bellows that it appeared on)
    -10- independent of film processor company
    -11- usually one spot on film but sometimes two spots
    -12- two spots may be of different exposures

    I have worked on this problem for almost a year now and I am still baffled. I have contacted Mr. Canham and other photography people. All have done their utmost to assist me with this problem, but so far we are mystified. In the future I will drape the bellows when photographing, but this is not my preferred solution. I am hoping that another photographer has seen this difficulty and has solved it.

    Best wishes --- AllenClick image for larger version. 

Name:	P5010024.jpg 
Views:	131 
Size:	75.9 KB 
ID:	98310

  2. #2

    Join Date
    Mar 1999
    Posts
    769

    Re: Unexpected 'optical spots' on film

    A number of possible explanations and it is possible you have already ruled out some/all.
    1) Pinhole in bellows or lensboard (although you appear to have ruled out bellows). Can act as a pinhole camera and form an image, especially of bright objects.
    2) Have sometimes seen this resulting from developing errors - air bells, which cause uneven uptake of developer.
    3) Film quality control issue. Are these all from the same emulsion number?

    Cheers, DJ

  3. #3

    Join Date
    Mar 2013
    Location
    Bethel, Maine
    Posts
    163

    Re: Unexpected 'optical spots' on film

    From the information provided it does appear that film may be the common denominator. Can you comment on that please?

  4. #4

    Join Date
    Dec 2012
    Location
    Superior, WI
    Posts
    22

    Re: Unexpected 'optical spots' on film

    Quote Originally Posted by redshift View Post
    From the information provided it does appear that film may be the common denominator. Can you comment on that please?
    I had not thought of film before. I purchased 200 sheets 8x10, removed the cardboard boxes leaving the metalized paper, stored all in freezer protected by cardboard and tinfoil. Periodically I remove 20 sheets, thaw for a day, and cut up in the dark to make 40 sheets of 5x7 with a wheel cutter and aluminum jigs for positioning. Afterwards I store at room temperature in nested boxes. Consistent with your hypothesis I purchased the 200 sheets of 8x10 film 3-1-2012. I haven't been able to match up the faulty film concept with only seeing the spots on film when the sun is out??? Still perplexing to me, but thanks for your insight.

    Best wishes --- Allen

  5. #5
    Resident Heretic Bruce Watson's Avatar
    Join Date
    Sep 2003
    Location
    USA, North Carolina
    Posts
    3,150

    Re: Unexpected 'optical spots' on film

    Quote Originally Posted by AA+ View Post
    I had not thought of film before. I purchased 200 sheets 8x10, removed the cardboard boxes leaving the metalized paper, stored all in freezer protected by cardboard and tinfoil.
    I might be wrong about this, but IIRC the metalized paper bags are not guaranteed to be light proof. The cardboard boxes are. The purpose of the bags is to maintain the clean dry atmospheric conditions the film was made in. It would be disastrous for the film to get damp enough for it to stick together, and the bags' design function is to prevent that. For years of shelf storage.

    In meeting that environmental protection function, it's conceivable that the bags will also be light proof, but if they are you are essentially just getting lucky.

    Does this have any connection with your posted problem? Probably not. That problem looks like pin hole light leaks from your bellows to me. If that's true, you'd only likely see 'em when the sun is shining on the bellows in just the right place, at just the right angle. Which might explain why they seem to "wander" around a bit and only show up with certain scenes.

    Easy to check for this by taking the camera into the darkroom, extending the bellows, stick a light in, and turn off the room light. If the bellows are completely light tight, you'll know. Else, you'll know that too. Quick and easy test.

    And just because your bellows is new, doesn't mean it's immune.

    Bruce Watson

  6. #6

    Join Date
    Dec 2012
    Location
    Superior, WI
    Posts
    22

    Re: Unexpected 'optical spots' on film

    Quote Originally Posted by Bruce Watson View Post
    I might be wrong about this, but IIRC the metalized paper bags are not guaranteed to be light proof. The cardboard boxes are. The purpose of the bags is to maintain the clean dry atmospheric conditions the film was made in. It would be disastrous for the film to get damp enough for it to stick together, and the bags' design function is to prevent that. For years of shelf storage.

    In meeting that environmental protection function, it's conceivable that the bags will also be light proof, but if they are you are essentially just getting lucky.

    Does this have any connection with your posted problem? Probably not. That problem looks like pin hole light leaks from your bellows to me. If that's true, you'd only likely see 'em when the sun is shining on the bellows in just the right place, at just the right angle. Which might explain why they seem to "wander" around a bit and only show up with certain scenes.

    Easy to check for this by taking the camera into the darkroom, extending the bellows, stick a light in, and turn off the room light. If the bellows are completely light tight, you'll know. Else, you'll know that too. Quick and easy test.

    And just because your bellows is new, doesn't mean it's immune.
    Thank you for your thoughtful response. Attempting to answer...

    -1- lightbulb test of bellows. I have already done that many times with the old bellows. Your point about the new bellows is well taken. Mr. Canham told me that one would be amazed at how wretched bellows could be and still work. On the old bellows, I found a light-leak in a fold far more tiny than the point of a common pin. I plugged the hole with liquid electrical tape inside and out. The 'optical spots' continued. I have not done the test with the new bellows.
    -2- metalized paper bags leaking light. I imagine that the cardboards within on either side of the film would prevent or hinder fogging from leaky bags. My story in this regard is that long ago a photoprocessor developing my 5x7s placed 6 undeveloped pictures between 5x7 cardboards and then turned on the light!!! It took him quite a while to realize his mistake. He developed them anyway. The picture centers were perfect, but the edges of the pictures were fogged by the light. Some of the fogging extended only a fraction of an inch inward on some films.

    I took my latest 'optical spot' picture with a 72mm lens that greatly compressed the new bellows, which I think would tend to suppress light leakage from the compression alone. Other pictures with the new bellows extended did not exhibit the fault.

    Anyhow this problem is a tough one, and I thank you for taking the time to pass your knowledge on. All suggestions are important to me.

    Best wishes --- Allen

  7. #7
    retrogrouchy
    Join Date
    Mar 2010
    Location
    Adelaide, Australia
    Posts
    832

    Re: Unexpected 'optical spots' on film

    The spots look much too large and soft-edged to be pinhole images of the sun. That double-spot on the example image you've posted makes me think that this could be a chemical issue: see the slightly-darker line separating the two spots. It's pretty straight and cuts into the circular region of both spots, cutting moreso into the larger spot if anything. That implies to me that the spots are not caused by two blinks/glints of light.

    They look sort of like bubbles in their shape to me. If there was a bubble forming on the film surface during the reversal or CD stages, the result would be a pale spot like this.

    How physically large are the spots? Is that a full-frame 5x7 you've posted or is it a crop?

    Since you're cutting down 8x10, do you know if maybe the spots are concentrated into one region (one corner?) of the 8x10 frames? Condensation might be an hypothesis worth considering: are there big temperature swings or high humidity where you store the cut film?

  8. #8

    Join Date
    Mar 2013
    Location
    Bethel, Maine
    Posts
    163

    Re: Unexpected 'optical spots' on film

    I'd still keep the focus on the film. Buy a small quantity of the same type of film that doesn't need to be cut down. See if the problem goes away. A little expense to narrow the search for the problem. The issue with the problem only happening on sunny days may only be coincidental.

  9. #9

    Join Date
    Dec 2012
    Location
    Superior, WI
    Posts
    22

    Re: Unexpected 'optical spots' on film

    Thanks to polyglot and redshift for your responses. I feel they are helpful.

    -1- The picture I posted is full frame 5x7
    -2- I have cut 8x10 for years without difficulty until now.
    -3- 'optical spots' are independent of photo finisher company.
    -4- I store in Superior, WI so I have moderate temperatures and moderate humidity, no condensation at all.

    From the various replies I am inclined to think that the problem could be pre-exposed film possibly during manufacture. My mind is still open.

    Best wishes --- Allen

  10. #10
    Resident Heretic Bruce Watson's Avatar
    Join Date
    Sep 2003
    Location
    USA, North Carolina
    Posts
    3,150

    Re: Unexpected 'optical spots' on film

    Quote Originally Posted by AA+ View Post
    -1- lightbulb test of bellows. ... I have not done the test with the new bellows.
    ...
    I took my latest 'optical spot' picture with a 72mm lens that greatly compressed the new bellows, which I think would tend to suppress light leakage from the compression alone.
    The problem may not be the bellows assembly itself, but the attachment of the bellows to the front and rear frames. Which is why you might consider running the light bulb test with the new bellows. If you do the test, the worst that can happen is you completely rule out the bellows.

    You might want to do this with your 72mm lens mounted on the front frame to see if there are any leaks around the lens board.

    Probably not the problem, but easy enough to check off the list of possible causes.

    Bruce Watson

Similar Threads

  1. new Epson V700 and black spots - not dust spots
    By beichh4046 in forum Darkroom: Film, Processing & Printing
    Replies: 11
    Last Post: 23-Apr-2012, 09:44
  2. Scanner Optical Density vs X-Ray Film Optical Density
    By NancyRoberts in forum Digital Hardware
    Replies: 4
    Last Post: 21-Sep-2011, 15:29
  3. Black spots, white spots
    By jonathan_lipkin in forum Darkroom: Film, Processing & Printing
    Replies: 2
    Last Post: 13-Aug-2010, 08:35
  4. Unexpected film testing results
    By shannaford in forum Darkroom: Film, Processing & Printing
    Replies: 15
    Last Post: 30-Oct-2009, 13:07
  5. 4x5 film spots?
    By joeyrsmith in forum Darkroom: Film, Processing & Printing
    Replies: 8
    Last Post: 6-Sep-2009, 20:54

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •