ES EEE PER
PE URS EAN EEE TRE
The sampling aperture of the drum scanner is required to
pass all frequencies up to this limitted frequency.
For example, the sampling aperture for the color film SO-379
is need to be 60 x 60 um, which is equivalent to IFOV 30x30 cm
when the photo scale is 1:5000, and for othercolor film; 2448
and 2445, 80 x 80 um which corresopnds to IFOV 42x42 cm when
the photo scale is 1:5000, If smaller sampling aperture is
needed, the MTF of these color film must be restorated by
some image processing technique such as an optical filtering.
MTF decreases in the periphery of the image.
The limitted spatial frequencies were 5,6 lines/mm and 8,0
lines/mm, along and across the flight direction respectively.
So, the optimum size of sampling aperture becomes to 90 x 90 pm
which corresponds with IFOV 45 cm when the photo scale is
1:5000,
3-3 COLOR REPRODUCTION
Images of the 2nd color targets and the 3rd grey scale E
targets on the test film were measured by a microspectro r
radiometer and their spectral transmittances were transformed
to CIE, u-v chromaticity coordinates.
Table 2 shows the mean color differences on the ten colors
of all the tested films, filter conbinations, and the rankings
as a reference which indicate the smaller color differences.
From the table, it is found that the reversal aerial color film,
type 2448, had the best color reproduction and the SO-379 film
the worst among those three films.
Fig. 10 shows variations of the chromaticities of the
color targets on each film, In the figure, numerals of
l to 4 indicate the chromaticities of the grey targets repro-
duced on the each film, and Gl to G4 chromaticities of the
original gray targets, The reversal color film 2448 was
balanced to green-yellow color and reproduced colors had the
minimum color differences and its reproduced purties was
the highest, (4
For the 50-357 film, the green color is reproduced to be
yellowish, pale blue color also to be yellowish, and grey
to be yellowish.
4 CHANGE OF IMAGE QUALITY BY DUPLICATIONS
Duplicated images, which are distributed to users, are
printed on several color films or papers from an aerial color
