Nikon LS-4500AF - 12-Bit A;D and LUT (Look up Table)

43 Nikon Film Scanner LS-4500AF User's Manual
The film is inserted from the front, moved in sequence and scanned.
The LS-4500AF is a scanner of light source color switching type, film
moving type, and surface sequence type.
The machine has two optical systems, and scanning of both 4 x 5 inch film
and 35mm film is possible by switching between them.
12-bit A/D and LUT (Look Up Table)
The LS-4500AF has a 12 bit A/D converter.
12-bit resolution is thus possible (2
12
= 4096 levels). This can be converted
to 8-bit data (2
8
= 256 levels) by using an LUT (look up table).
The conversion from 12 to 8 bits is necessary because many systems deal
with image data in 8-bit form.
0
4096
256
Input
Output
If the number obtained by simply dividing the data by 16 (=4096/256) were
output, the LUT would be meaningless. The LUT has the ability to
condense data from 4096 levels to 256 levels, without a loss of white data
while maintaining keeping black gradations (high density side).
The LUT is used gamma (non-linearity) compensation of the output (as in
the case of a CRT monitor).
The LUT also provides for black tuning and white tuning.
It is possible to intentionally lose black data or skip white data.
9. Technical Tips on the LS-4500AF