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Data Mode
Data Mode delivers a single channel 12 bit raw Bayer
data image without compression. No image adjustment
other than white balance is applied. This raw data
could be described as a digital negative, which has to
be converted to an RGB image before it can be used.
Bayer Pattern - Color Filter Array
An imaging sensor can only differentiate a change in
luminance, not color. Hence, the incident light has to
be separated into color components. As the D-21 uses
a single chip, the color separation is done by means
of a color filter array (
CFA
). A CFA is a small mosaic
pattern of color filter dyes. Each pixel is covered
with one dye, so it only captures the luminance
information for one color component. One form of
a CFA is the
Bayer pattern
with red, green, and blue
sensing pixels, which is used for the D-21 sensor.
ARRIRAW Processing
As the RAW Bayer data only contains luminance
information, ARRIRAW processing assigns one color
component to each pixel, based on the CFA alignment
on the sensor. The image now contains three color
components, but only one component per pixel. To
obtain the remaining two color components for each
pixel they have to be interpolated from the surrounding
pixels – i.e. color reconstruction. There are different
methods for color reconstruction based on processing
speed vs. output quality. Before the RGB image is
ready for viewing, the colors need to be transformed to
the desired output color space (e.g. for output on HD
displays, print on film or digital cinema projection) and
the tonal balance has to be adapted using the intended
contrast characteristic. The output RGB images are then
stored e.g. as 10 bit log dpx files, 16 bit tiff files, or other
file formats, depending on postproduction requirements.
ARRIRAW data can be processed in production
quality using the ARRI software tool Image
Booster or can be output by ARRIRAW T-Link
(see below) certified recorders and playback
devices as live HD preview or production quality
images depending on their specifications.
Note: Please check the Image Booster reference
for more information on ARRIRAW
processing and output options.
ARRIRAW Output
When set to ARRIRAW, an output board
delivers the raw data with:
2880 x 2160 pixels in 1.33:1 (4:3) aspect ratio
•
using the full sensor aperture up to 25 fps,
2880 x 1620 pixels in 1.78:1 (16:9) aspect ratio
•
using the full sensor aperture width up to 30 fps.
The ARRIRAW output is sent over a
dual link HD-SDI connection.
