Silicon Imaging SI-2K, Руководство пользователя

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ShootingwiththeSI-2K
SI 2K Manual
At the heart of the SI-2K camera system is an Alta-
Sens 2/3" CMOS sensor with an overall dynamic
range of 69 db from the noise floor to white-clip.
Using an on-board A/D converter, data is con-
verted from analog signals on the CMOS chip to
a photometrically linear 12-bit signal that is then
transferred as RAW data over 1000BASE-T from
the camera head to the PC controller, whether it is
an external system in the case of the SI-2K MINI,
or the internal embedded system in the SI-2K.
Once the RAW data is inside the PC, its black-
clip level is calibrated and the linear 12-bits is
converted to 10-bits using a simple logarithmic
profile curve. This is a fixed value curve, designed
to give the maximum quality for creating an infor-
mation-rich digital negative without wasting bits
or encoding too much noise in the visual domain.
A logarithmic curve is used as it is a more natural
representation of the way the human visual sys-
tem reacts to light, and has a two-fold advantage:
it preserves the photometric dynamic range from
the 12-bit linear data (linear data is not gamma
corrected and would look very dark on a normal
monitor) while also optimizing the image for com-
pression into CineForm RAW™.
After the 10-bit LOG curve is applied, the image
is sent to the encoder and then written to disk
in the camera-native color-space and no white-
balance is applied. This minimal amount of sig-
nal processing allows for the maximum dynamic
range from the camera to be preserved into post.
All color information that is used to normalized the
data on the screen is saved as a separate layer
of metadata at the time of recording, allowing the
end-user to make an unlimited amount of adjust-
ments in post by adjusting the metadata layer
rather than making non-reversible adjustments to
the RAW data.
Introduction And RAW Pipeline
CMOS Sensor
RAW 12-bit Linear
Black Calibration
10-bit LOG Curve
CineForm Raw Codec
Layer 3: Filters & Effects
Layer 2: “Look” Metadata
Layer 1: RAW 10-bit log
Figure .1: RAW Data Pathway
Exposure Control