User manual

58 Shooting with the SI-2K SI 2K Manual
By exposing “to the right”, the D.P. sets the camera’s exposure so that for a
given scene, as much of the scene value information as possible is contained
towards the right-side of the histogram without letting values clip. Using this
methodology in combination with the 6-zone exposure meter, the D.P. can ex-
actly visualize the exposure for a given scene, knowing not only the value dis-
tribution of the pixel values in the scene, but what pixels correspond to the
different values settings, especially those pixels that are at or near the clip value
of the sensor’s ADC.
Using .look 3D LUT files
The SI-2K camera system has an integrated 3D LUT engine that utilizes IRIDAS
.look files and color-correction data from Speedgrade OnSet. By exporting a
DPX color image to Speedgrade using the SAVE IMAGE button (see Chapter
3), the user is able to color-correct the RAW 10-bit log data, and then re-apply
that color-correction information back into the camera for real-time shooting
and visualization of their desired “look”. The implications of this workflow are
quite powerful, considering that a 3D LUT can describe any series of non-
linear color-correction changes including gamma correction, saturation, hue-
shifts, selective secondary corrections, etc. This essentially makes the camera
a “blank-slate”, where using the RAW 10-bit log data as a reference source, an
unlimited amount of variations and/or visualizations can be achieved to make
the camera “look” like almost anything imaginable.
During recording the .look file information is saved in a layer above the RAW
10-bit log data, and is rendered in real-time during playback at the codec level.
This makes the .look metadata non-destructive, and .look files can be swapped
out in the post process if they are not deemed to be the desired LUT the D.P.
would have applied to the footage. Because the .look file is a portion of the real-
time pathway in the codec decoding engine, swapping a .look file is a real-time
operation that does not require re-rendering for visualization. Also because the
CineForm RAW codec engine has a 32-bit floating point processing pipeline,
any information that a .look file might “clip” when applied to the RAW data can
be retrieved using the host color-correction filters of the NLE, DI, or composit-
ing application as long as the RAW data itself is not clipped.
In the film world, the relationship between a .look file and the RAW 10-bit log
data is analogous the difference between the original color negative and the
film print. Typically the D.P. exposes the negative, and then during the printing
stage, he will apply color-corrections and exposure adjustments to “print-up” or
“print-down” the negative and achieve his desired results. As a non-destructive
metadata layer above the RAW 10-bit log data, the .look file modifies the RAW
data in a similar way, only that now an unlimited amount of variations in film-
prints can be visualized non-destructively if one chooses. Furthermore the DP
can shoot on-set and use the .look 3D LUT files to non-destructively visualize
what the end-print will look like, and adjust his lighting scenarios and fill-ratios
to fit the look he is trying to achieve.