METHOD FOR PREPARING FULL COLOR POSTERS OF VERY HIGH QUALITY AND SHARPNESS

PROCEDE POUR PREPARER DES AFFICHES COULEURS COMPLETES DE TRES GRANDE QUALITE ET DE GRANDE NETTETE

Description

CA 02228690 1998-03-OS
1
METHOD FOR PREPARING FULL COLOR POSTERS OF
VERY HIGH QUALITY AND SHARPNESS
This invention is concerned with a method for preparing full color posters
of vend high quality and sharpness on standard photographic papers.
To prepare a quality full color poster from any digitized image, with or
without text, it is of conventional practice to produce full-sized color
separation
negatives of the scanned original art work, and then to use these separation
negatives to produce the poster either by contact on a photographic paper, by
serigraphy, or by four-color process printing.
This conventional method is efficient but quite expensive if the number of
posters to be prepared is small.
It has now been discovered that full color posters can easily be prepared
in small numbers at a substantially lower cost by a method comprising the
steps
of:
a) producing color separation negatives of the digital file to be
reproduced as a poster, these negatives being usually four in
number and of full size, or sized to fit a photographic enlarger (4" x
5" to 11" x 14" in size);
b) producing the corresponding color separation positives of the color
separation negatives produced in step (a);
c) printing the separation positives in successive order by direct
application and exposition of each of the same onto a display
transparency film or color negative material so as to form a full
color negative;
d) exposing the full color negative obtained in step (c) to a tinted light
in order to vary the base color of this negative as much as
necessary to obtain any requested color tone; and
e) using the exposed full color negative of step (d) to produce the
requested reproduction, i.e. the requested poster, either of the
same size or of an enlarged size, in much the same way as a
conventional continuous-tone color negative would be used.


CA 02228690 1998-03-OS
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The same results may be achieved by directly producing color separation
positives of the digital file, instead of producing color separation negatives
as
called for in step (a) and thereafter producing the corresponding color
separation
positives as called for in step (b). In such a variant, steps (c) through (e)
remain
the same.
It has also been found that it is possible to change the optics of an
existing imagesetter of the same type as conventionally used to produce color
separ~~tion negatives or positives, in order to mechanically combine steps (a)
through (c), thereby producing a single screened film with all four colors
printed
on it - in other words, a full color screened negative.
The display transparency film sold by KODAK under the trademark
DURP,CLEAR has proved in practice to be particularly useful to produce the
full
color negative disclosed in step (c) or in the converted imagesetter. Other
types
of clear base photographic products can be used but have proved so far not to
give as good results. Color negative material can be used but it is generally
less
precise, and produces less sharp prints.
The above method has been tested with great success, using digital files
of a minimum of ten (10) MB. It allows the production of large, full color
posters
of vend high quality and sharpness from digital files, small or large, in a
very
simples yet efficient manner.