Please define "thin" and "thick" negatives

Discussion in 'Film and Processing' started by railhead, Apr 12, 2006.

  1. TOTAL newbie question, and I search -- but found no solid answer.

    I keep reading talk of thin and thick negatives, but I'm not sure what people are referring to.
    Are you saying a negative is thin because it doesn't have a lot of contrast, and a thick neg
    does?

    Or, are you literally talking about thickness?
     
  2. Thick means dense, dark, or "doesn't allow much light to get through". Thin means almost clear, or "does allow a lot of light to get through".
    <p>
    The terms don't directly say anything about contrast, though thin negatives are often low contrast, as well.
    <p>
    Thin negatives happen because of underexposure and/or underdevelopment. Thick negatives happen because of overexposure and/or overdevelopment.
     
  3. Thanks!
     
  4. I've never heard the term "thick" applied to negatives, except as a distinction between "thin" emulsions (the physical depth of the coating applied to the film base) and "thin" emulsions. Thick emulsions are ususally also "faster" (more sensitive to light) than "thin" emulsions.

    In terms of a developed negative and the anount of silver retained after fixing, the terms are "thin" and "dense."
     
  5. Our valiant moderator James Dainis posted negative scans of 0 +5 -3 exposured in this archived thread. I'd say +5 is thick and -3 is thin, though I've seen thinner.
     
  6. Richard is partially correct with his definitions of "thin" and "thick" negatives. There's a little more to the story. The terms "thick" and "thin" are relative terms and subjective when one refers to negative densities. This should not be confused with high and low contrast negatives. Exposure is the primary variable affecting density. Development is the variable that, to a greater degree than other variables given a scene of average brightness ratio, controls contrast.

    Assuming a scene of average brightness ration, the following generalizatios hold true:

    Underexposure and reduced development = low density and low contrast negatives.


    Underexposure and normal development = low density negatives with a bit more contrast than if the film was subjected to reduced development.

    Underexposure and extended development = low density and high contrast negatives. This is typical for "push processed" films.

    Normal exposure and development = Average density and contrast negatives. This is pretty near to what the manufacturers get with ISO testing to determine film speed and contrast index for a given film.

    Normal exposure and extended development = Slightly higher than normal overall density with a boost in contrast. Densities in the midtones and highlights are pushed up the scale while the shadow densities gain little extra density.

    Normal exposure with reduced development = Slightly lower than normal density and reduced contrast. The highights develop fairly early in the development cycle and continue to build density during the development cycle. The shadow areas take a bit more time to start forming up, but development completes fairly quickly in these areas. The reduced development time prevents the highlight areas from becoming too dense because development is halted before these areas have reached their potential maximum density.

    Overexposure and under development = Possibly higher than normal density with reduced contrast for the same reasons stated in the previous paragraph.

    Overexposure and normal development = Higher than normal density. Contrast can go either way depending on the characteristics of a particular film and the degree of overexposure and plus development.

    Overexposure and extended development = Higher than normal density and contrast. These are sometimes called "bulletproof" negatives. Taken to extremes, the contrast can be lessened since all the recorded tones are forced up into the shoulder area of the film's contrast curve where it begins to flatten out.
     
  7. Frank, thanks for that explanation. I don't have anything to contribute, but would like to know how this issue applies to trannies, this being my main medium. I have read that for printing purposes you can also expand or contract their contrast range a little with OE/UD or UE/OD.
     
  8. Richard,

    Are you sure that's right? If "thick" doesn't allow a lot of light to get through, wouldn't that contribute to "underexposure"? Conversely, if "thin" allows a lot of light through, wouldn't that potentially cause "overexposure"? Just when I thought I had these figured out...
     
  9. Bill J. wrote:
    "Richard,
    Are you sure that's right? If "thick" doesn't allow a lot of light to get through, wouldn't that
    contribute to "underexposure"? Conversely, if "thin" allows a lot of light through, wouldn't
    that potentially cause "overexposure"? Just when I thought I had these figured out..."

    Bill, Richard is correct. I think you're skipping ahead and talking in terms of the print,
    while Richard is referring to qualities of the negative. In terms of the print you are correct
    in thinking that a dense (over-exposed) negative would need a longer exposure to achieve
    a normal looking print. In terms of the print a thin negative (underexposed) would need a
    relatively short time to achieve a normal looking print.
     
  10. Matthew,

    Thanks for the clarification. I think I got it now.

    Bill
     
  11. James G. Dainis

    James G. Dainis Moderator

    If the negative received no exposure to light, like forgetting to take the lens cap off on a rangefinder, it would be very thin indeed. It would be clear except for the film base color. Shoot light through that thin clear negative in an enlarger to photo paper and all it would do would be to burn the paper totally black giving an image of what the film "saw", nothing, total blackness.
     
  12. Thank you James for the simplified and clear answer. It is tricky, because you have to think of the negative in reverse of a print. So if your negatives are vague they are UNDER exposed, and if they are really dark they are OVER exposed. Just the opposite of how the prints are.
     
  13. James G. Dainis

    James G. Dainis Moderator

    Steve, that is why I find it a bit irritating if people show me a photo and ask if it is under or overexposed. I usually ask, "What does the negative look like?" When a print is made in the lab, an analyzer, similar to a meter in a camera, sets the print exposure. The analyzer can be "fooled" by too much white, such as in a snow scene, and make a print that comes out too dark. Judging by the print, you would think that you had underexposed when taking the photo but your exposure could have been dead on. People who process their own film see the dense (thick) or thin frames as soon as they pull the roll of developed film off the developing reel.
     

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