Overexposition

Discussion in 'Darkroom Developing and Printing' started by piterengel, Aug 29, 2003.

  1. piterengel

    piterengel Guest

    Hi, I've overexposed a Kodak HIE roll, at least 2 stop more. What time
    of develop can I use compared with the right one used to develop a
    well-exposed roll? I.e., if 9 min with ID-11 is OK for a roll for
    which I've used 400 ISO of sensibility, what is the time you suggest
    for the same developer for a 2-stop overexposition?

    Thanks

    piterengel

    P.S.: is it true that for Infrared films it is better to set on camera
    400 ISO in summer and 100 ISO in winter? And is fo, why?
     
    piterengel, Aug 29, 2003
    #1
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  2. You can't really compensate for overexposing by reducing
    development. Reducing developing time will reduce contrast.
    It will also reduce overall density. So the negatives may be
    easier to print but will need to be printed on more
    contrasty paper than usual.
    For most film reducing development time by about 30% will
    reduce contrast by about one paper grade and film speed by
    not quite a stop.
    I would not reduce development time more than this.
    The speed setting will depend on how much infra-red light
    there is. On average away from the equator, there is
    considerably less in winter than in summer.
    However, since the amount of IR is hard to measure with a
    normal exposure meter you must test. Bracket about one stop
    more and one stop less than you think is correct. Even two
    stops more and less may be helpful if yuo have no idea of
    the amount of IR light. One test roll will let you know how
    to expose for those particular conditions in the future.
     
    Richard Knoppow, Aug 29, 2003
    #2
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  3. I am not sure I understand this right. I think you are
    asking why the speed of the film varies with time of year
    while visible light sensitivity does not vary. The amount of
    infra-red light may become less of the overall light. I am
    not sure this is always true. Again, since few exposure
    meters are accurate for IR one must experiment to get
    correct exposures.
    Somewhere there must be a chart which shows the amount of
    IR in sunlight at different times of year and different
    latitudes of the Earth.
     
    Richard Knoppow, Aug 29, 2003
    #3
  4. That's an astronomy question...

    ....and the answer is, I don't think the proportion of IR in sunlight varies
    appreciably. If anything, when the sun is low in the sky (in the winter),
    the total light is cut quite a bit, but the proportion of IR may be a bit
    higher.

    If there's variation, it's not winter vs. summer; it's high sun vs. low sun.
    Summer, near sunset, should be the same.

    I wonder if the original idea was that there is more vegetation (bright in
    the IR) in the summer.

    But my first guess would be that there is no significant change; the same
    meter setting should work year-round (given that it's not perfect in the
    first place).


    --
    Clear skies,

    Michael Covington -- www.covingtoninnovations.com
    Author, Astrophotography for the Amateur
    and (new) How to Use a Computerized Telescope
     
    Michael A. Covington, Aug 29, 2003
    #4
  5. piterengel

    piterengel Guest

    Very simple, really. I've taken the first 4 shoot of the roll setting
    camera on 100 ISO. The guy who were with me told: "We are on the
    beach, it is summer, so set camera on 400 ISO. 100 will be right
    during winter". And I did. So I had a unique roll exposed in 2 ways.
    After developing it in ID-11 I've seen the first 4 photos very
    different (darker being negatives) than the whole other. The matter
    now is that BEFORE knowing this man I've exposed an entire roll at 100
    ISO, always on the beach. And of course I've not yet developed it!
    Understood my matter? Photos are not critical, I'm a beginner on IR so
    I've taken "normal" photos (most of them are landscapes). But I would
    like to know how I can operate to obtain the maximum from my wrong
    work!

    Best regards

    piterengel
     
    piterengel, Aug 29, 2003
    #5
  6. That's clearer:) Do the ISO-100 pictures look too dense
    and the ISO-400 ones look normal? If this is the case I
    would develop the ISO-100 film in full stength Microdol-X or
    in Ilford Perceptol. Both require about one stop more
    exposure than the ISO exposure. If you then reduce
    developing time by about 25% you will lose some more speed
    and lower the contrast somewhat. The negatives should then
    be of reasonable density although you might have to print
    them on more contrasty paper than normal.
    IR film has less overexposure margin than regular film but
    will still take overexposure better than under exposure. 2
    stops overexposure should be within the latitude of the
    film. Normal development would probably result in somewhat
    dense negatives which would make good prints but require
    long print exposure time. Its _not_ a disaster.
     
    Richard Knoppow, Aug 29, 2003
    #6
  7. But remember, the altitude of the sun goes down to zero every day, even in
    the summer (at sunrise and sunset). So saying "the sun is lower in the
    winter" is a half-truth. It is lower at noon in the winter than at noon in
    the summer. But it is low some of the time every day.
     
    Michael A. Covington, Aug 30, 2003
    #7

  8. HIE does not have an ISO speed. Were you sing it with a red filter?
    I would not expect much from beach shots with HIE. Leafy folliage and
    grass are often chosen to be included as subject matter on HIE,
    because these things reflect a lot of infrared. I don't understand
    what you're doing. Please explain better.


    100 will be right
     
    Michael Scarpitti, Aug 30, 2003
    #8
  9. Using a red filter over the lens blocks out all of the ultraviolet,
    violet, blue, green, and yellow light, leaving only red and infrared
    rays. The film is sensitive to ultraviolet, violet, blue, green,
    yellow, red, and infrared rays. ISO is calibrated for use with meters
    that measure violet, blue, green, yellow, and red rays. Since you
    cannot measure the amount of infrared with your ordinary meter, you
    have no way to predict exposure with precision, except when using the
    same equipment under exactly the same indoor conditions. Since the
    amount of infrared varies throughout the day and throughout the year,
    the best advice is to bracket your exposures.
     
    Michael Scarpitti, Sep 1, 2003
    #9
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