At 17:57 1/2/02, Skip Williams wrote:
Bill,
My minilab prints Kodak T400CN with perfect blacks and absolutely no color
tinting. They have a custom filter setting for the film and are very
careful when printing B&W negatives onto color paper. They use an Agfa
minilab (model unknown).
I'm not an expert, but I'd bet $100 that many prints could be corrected by
proper filtration. Is this a setting error? Beats me.
Skip
Even Kodak admits to a few things if you read the "fine print" in their
technical publications about the film and about their chromogenic B/W
paper! Not only is there a potential issue when printing on color paper,
there's also an issue with a potential "color cast" printing on chromogenic
B/W paper depending on the lighting under which the print is viewed! The
two items below are quoted from these publications.
-- John
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From Kodak's publication F-15 about printing B&W+400 on color paper:
http://www.kodak.com/global/en/consumer/products/techInfo/f15/f15.pdf
Note: Occasionally, the image tone of prints may vary slightly from
neutral because of differences in printer setups. The tones of your prints
can range from a cool, bluish black to a warm brown or olive black
depending on the finisher. This subtlety will add an extra dimension to
your images.
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From Kodak's publication G-4006 about its Portra chromogenic B/W paper:
http://www.kodak.com/global/en/professional/support/techPubs/g4006/g4006.pdf
Image Hue
Because PORTRA Black & White Paper uses colored dyes to form images, it
can exhibit slight variations in hue (when we use the term hue in this
publication, we are referring to the image tone). In fact, viewers may be
more sensitive to hue variations in these prints than they are to hue
variations in color prints.
Note: For hue sensitive applications, conventional black-and-white
(silver) paper will provide the best performance.
While some processing conditions may have an effect, the most likely
contributor to hue variations is the color quality of the viewing light.
Use a light source such as daylight, tungsten, or
tungsten-halogen/quartz-halogen. These sources provide continuous
frequency of energy in the visible spectrum and will result in a neutral
rendering of the image. Where there is little control over viewing
conditions, a conventional black-and white (silver) paper might be a more
appropriate choice.
Other illuminants may result in a warm image tone. For example, a
silver-based black-and-white image reflects all frequencies of light
equally, so a slight deficiency in one color of the viewing light will not
have an adverse effect. However, a chromogenic image (e.g., an image on
PROFESSIONAL PORTRA Black & White Paper) is formed by dyes that have
specific color absorption and reflection characteristics. Dyes do not
reflect all frequencies of light equally. Instead, they reflect only
specific wavelengths of red, green, and blue light. So, if a
non-continuous light source (e.g.mercury vapor and
low-energy/high-efficiency fluorescent tubes) is deficient in green light,
a chromogenic print may look very pink (magenta), depending on the dye and
the green-region deficiency of the light source.
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