Autochrome - Printing from Plate - Making Tri-color Filters - Wratten Equivalents

Autochrome - Printing from Plate - Making Tri-color Filters - Wratten Equivalents

  1. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Autochrome - Printing from Plate - Making Tri-color Filters - Wratten Equivalents - Autochrome - Printing from Plate - Making Tri-color Filters - Wratten Equivalents

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  2. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    For those who do not want the trouble of making the
    niters, the Wratten & Wainwright gelatine film filters of
    the requisite size may be bound up between glasses. The
    numbers of their filters are, for the red No. 29 or F,
    for the green No. 61 or N, and for the blue No. 50 or L.

    A moment's consideration will show us that as we
    want to reproduce the red, we must use a red-sensitive
    plate, and it will be found more satisfactory to use panchromatic
    plates for all three negatives, as by doing
    so the gradation in the three negatives will be more
    alike than when we use different kinds. There is some
    latitude here, as we are able to modify the final result,
    and one might choose a panchromatic for the red, an
    isochromatic for the green and an ordinary plate for the
    blue filter exposures; but it cannot be advised. Whether
    a fast or slow panchromatic plate be used is of no particular
    moment; the slow kind will give as good results
    as the fast and is less likely to fog. At the same time
    it must be borne in mind that we are making negatives,
    not transparencies, and this must be kept in view in
    developing. Brilliant-looking plates with clear glass
    shadows are not the desideratum; but soft negatives,
    rather thin in the high-lights, with fully exposed shadows,
    should be aimed at. It is immaterial what developer is
    used, and the beginner should use that to which he is
    accustomed. Naturally the desensitizing process may
    be adopted, and the plates should be backed.
    In the reproduction of a screen-plate it is clear that
    we might place it with the film in contact with the sensitive
    plate. Then we should have the color elements
    reproduced quite sharp, and every negative would be
    broken up into minute dots corresponding in size. For
    some positive processes this might not be a disadvantage,
    but in the case of the separate system in which the positive
    is bound up with a viewing screen, we cannot obtain
    contact with the sensitive surface. The result will
    be more or less want of sharpness, but this will not be
    of serious moment, and it breaks up the screen pattern,
    so that almost closed or continuous tone negatives are
    obtained. Actually it is advisable to follow the same
    plan with an autochrome, that is, to interpose between
    the sensitive surface and the picture film a colorless
    transparent medium of greater or lesser thickness.
    There are some very simple mathematical formulas
    by which we can tell not only what ought to be the thickness
    of the intervening medium, but also the distance
    of the light source, and the resulting want of sharpness
    in the resulting negatives. But one of the main ideas
    in this little book has been to avoid, as far as consistent
    with clarity, mathematics and deep theory, so that it
    will be assumed that it is required to make the negatives
    from autochrome and Paget pictures.

    https://archive.org/details/practicalcolorph00walliala

    PRACTICAL COLOR
    PHOTOGRAPHY
    BY
    E. J. WALL, F.C.S., F.R.P.S.
    Author of
    "The Dictionary of Photography,"
    " Carbon Printing," etc.
    SOUTHERN
    AMERICAN PHOTOGRAPHIC PUBLISHING CO.
    BOSTON 17, MASSACHUSETTS
    1922

    COPYRIGHT, 1922, BY
    AMERICAN PHOTOGRAPHIC
    PUBLISHING CO.
    Entered at Stationers' Hall
    PRINTED IN THE UNITED STATES OF AMERICA
    Electrotyped and printed, June, 1922
    THE PLIMPTON PRESS
    NORWOOD, MASS. U.S.A.