Nikon LS-4500AF - Manual (Page 65)

45 Nikon Film Scanner LS-4500AF User's Manual
Prescanning and absolute light energy
Prescanning is the function which sets the light energy by scanning the
black (maximum density) and white (minimum density) of the film.
Therefore, the meanings of the numbers differ according to the film. In
one film 10 steps (of 256 steps) may correspond to a density of 1.5, but
correspond to a density of 1.7 in some other film.
It is easier to understand the scanner as a TV camera than as a densitom-
eter.
A TV camera works with a diaphragm which opens in order to take in more
light if the subject is dark. The light energy each time scanning is per-
formed is not absolute light energy, but varies according to the film.
While it is possible to set the light energy used by the LS-4500AF, the pre-
scanning mode is recommended in order to obtain a better image.
Auto setup is also possible by prescanning. Compensations can be made, if
necessary.
Sharpness
Sharpness adjustment is achieved by means of a 3 x 3 matrix, which can be
defined by the user. This is more easily understood if we use a simple
figure. To simplify the explanation, consider sharpness as one-dimen-
sional. Suppose that there is an output wave form as shown in the figure,
and assume that the sharpness coefficient is -20 140 -20. This means
multiplying the picture element of a subject by 120% and adding the
elements of both ends multiplied by -20% (subtracting the elements at both
ends multiplied by 20%). When this filter is applied to the wave form
shown in the left-hand figure, the result will be as shown in the right-hand
figure. A change can be seen at the rising point. The edge section is
emphasized, as shown here.
9. Technical Tips on the LS-4500AF