Are All B&W Films Balanced for Tungsten?

Discussion in 'Darkroom Developing and Printing' started by Dan Quinn, Sep 7, 2003.

  1. Hi Michael,


    Where is it indicated what energy source was used?


    Francis A. Miniter


     
    Francis A. Miniter, Sep 11, 2003
    #21
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  2. Dan Quinn

    Dan Quinn Guest

    RE: "Francis A. Miniter" <>

    Hi Mr. Miniter
    Neither Agfa or Kodak specify. Both show curves with high blue values;
    way out of line for "balance" if balance is a fairly uniform response to
    the "photogenic" spectrum. Ilford's balance is at 2850K.
    The daylight Mr. Scarpitti refers to is likely 5500K; daylight color
    film. A & K should make it plain just what temperature is used.
    It is obvious that "...All B&W Films..." ARE balanced for tungsten.
    In fact the tungsten speed is the films real speed. Higher daylight speeds
    are blue & green speeds. Corollary to this is the need to use filters in
    daylight. They are needed to provide the balance, fidelity, otherwise
    lacking.
    In a previous post Mr. Scarpitti explained the reason for the spikes
    at the blue end. BTW have you taken a look at the graph for FP4+? Dan
     
    Dan Quinn, Sep 11, 2003
    #22
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  3. Dan Quinn

    J Stafford Guest

    Typo? B&W film is typically relatively insensitive to green. Or has
    something changed overnight?
     
    J Stafford, Sep 11, 2003
    #23
  4. At the bottom. It's called 'equal energy' (though not stated). This
    corresponds more or less to daylight.
     
    Michael Scarpitti, Sep 11, 2003
    #24
  5. Dan Quinn

    Dan Quinn Guest

    RE: (J Stafford) wrote

    I may have had in mind the CC equivilants of conversion filters
    such as 85, 85B, etc. The CC equivilants incorporate a small
    amount of magenta; minus green.
    At 2850K all of Ilford's films show very good green response. FP4+
    is interesting. It has a depressed blue and smooth increase through
    green then continues upward to deep red; 640nm.
    The important point to keep in mind, to my thinking, is that
    Ilford does make, at 2850k, color balanced B&W film. At other
    color temperatures the balance does not exist.
    I think they should have graphed at 3200K. Are they fudging? Dan
     
    Dan Quinn, Sep 11, 2003
    #25
  6. Dan Quinn

    J Stafford Guest

    To my way of thinking, they are fudging, Big Time.
     
    J Stafford, Sep 12, 2003
    #26
  7. Dan Quinn

    Peter Irwin Guest

    The Ilford graphs appear to simply tracings of the output
    of a wedge spectrograph. It is normal to use incandescent
    light as a source. Kodak used to do it this way back before
    they got a lot more sophisticated about it. (See p.82 of
    From Dry Plates to Ektachrome film by Kenneth Mees)

    There are a few interpretability problems with wedge spectrograms:
    1) They do not provide very precise quantitative information.
    2) While one can make comparisions between measurements for
    different films made on the same set-up, comparisons between
    wedge spectrograms made at different laboratories are likely to
    be misleading.
    3) They are wildly inaccurate at the extreme violet/ultraviolet
    end, and the response fall-off at that end should not be assumed
    to be anything other than a measurement artefact.

    I think you are pretty safe in using Ilford's information from
    the wedge spectrograms to compare the spectral response of one
    Ilford film with another, but it does not appear to be safe to
    compare their graphs with those of other manufacturers.

    Peter.
     
    Peter Irwin, Sep 12, 2003
    #27

  8. Earth to Dan: You are going to be using them in daylight, right? You
    need a yellow-green filter. Stop all this nonsense.
    No such thing exists. B&W film is not 'colour-balanced' because there
    are no colurs in B&W film!
     
    Michael Scarpitti, Sep 12, 2003
    #28
  9. Dan Quinn

    J Stafford Guest

    Mike, did you learn nothing? :) B&W _is_ color withouth HUE. You know that
    in yoour heart. Get with it, man. I'm perfectly serious. If it were not
    color without HUE, you would not use filters, would you. Get hip to
    sensitive color correction and quit already with the gross contrast
    filters.
     
    J Stafford, Sep 12, 2003
    #29
  10. You misunderstand me.

    1. 'Colour-balanced' is a term with a specific meaning, referring to
    color films. It means that all three layers of the color emulsion are
    matched to the spectral distribution of the light source, to get
    proper reproduction of colours. It cannot BY DEFINITION be applied to
    B&W films.

    2. B&W films do not have a linear response to colours. You saw that
    all B&W films have a dimished response to yellow-green. That's why a
    yellow-green filter is used in daylight scenes to render a
    'normal-looking' B&W image. Using and 85B filter on B&W film WILL NOT
    do that.
     
    Michael Scarpitti, Sep 12, 2003
    #30
  11. Dan

    I am pretty sure the color temperature used for the
    spectral sensitivity curves is established by an ISO
    standard.
    The color sensitivity of B&W films is mostly determined by
    the dyes added to the emulsion to sensitise it to color. The
    mixture of halides and method of making the emulsion does
    have some effect on the relative amounts of blue and blue
    green sensitivity in addition to the dyes.
    All B&W films, except for chromogenic films, have excess
    blue sensitivity. Some, like the T-Max films, have less than
    conventional films but the blue sensitivity is still higher
    than for other colors.
    In addition there are variations in the amount of red
    sensitivity among films and the extension into the red end
    of the spectrum. These two should not be confused because
    they have somewhat different results. Kodak Technical Pan
    has both greater red sensitivity and somewhat greater
    extension. The greater sensitivity will tend to wash out
    skin tones. Technical Pan still has excessive blue
    sensitivity despite the extended red senstivity.
    It is also typical for older panchromatic films to have a
    dip in the green. This is due to the particular dyes used.
    T-Max films do not seem to have this dip.
    Most B&W films will be closer to the spectral sensitivity
    of the eye by using a No.11 (old X-1) light green filter in
    daylight, or a No.13 (old X-2) dark green filter in tungsten
    light.
    Kodak's chromogenic B&W films have a sensitivity peaked in
    the green approximating the sensitivity of the eye. This is
    one reason the tonal rendition of these films is different
    from silver image films.
    As far as the original question about color balance, the
    chromogenic films are the only ones which give approximately
    visual tone value for color without a filter. I don't know
    if they are balanced for daylight or tungsten. Another look
    at the graphs might show what color light was used to make
    them.
     
    Richard Knoppow, Sep 12, 2003
    #31
  12. If it's a daylight ISO speed I'd look for it in the ISO
    standards.
     
    Jan Brittenson, Sep 13, 2003
    #32
  13. Dan Quinn

    Dan Quinn Guest

    I thought 5500K to be the daylight standard. What color temperature
    would you assign to daylight? Dan
     
    Dan Quinn, Sep 14, 2003
    #33
  14. It's not all about color temperature... There are several
    standard illuminants, the most common being CIE D50 and D65,
    representing standardized versions of 5000K and 6500K, respectively.
    ISO imports these liberally in many standards. An example I have
    on hand is ISO/DP3664 which defines a light source for transparency
    viewing (based on CIE D50).

    There are many ISO standards for measuring film (e.g. ISO 5800:1987
    for color neg print film) and digital sensitivity. Obviously these
    will refer to one or more standard illuminants that are 1) usable
    in a lab, and 2) representative of sunlight. Those who care
    can go dig it up on their own. Here's a good place to start:
    http://makeashorterlink.com/?Y506316E5
    (http://collection.nlc-bnc.ca/100/200/301/nlc-bnc/bibliography_standards_apr96-ef/ebibl3c.htm)
     
    Jan Brittenson, Sep 14, 2003
    #34
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