ARRI ALEXA SUP 7.0, Pocket Manual, Page: 31 / 100

31
W
orking
with ALE
XA
• If Log C material is recorded directly onto SxS
PRO cards in an ALEXA, the camera’s MON
OUT is typically set to Rec 709. This activates
a conversion LUT, which is applied on the
monitoring output.
• Shooting images in Log C delivers the best
foundation for the colorist’s work, providing
the camera’s full latitude in an unconfined color
space. For output on HDTV, Log C images
need to be tone-mapped and transformed into
the target color space. This is typically done
using a 3D LUT provided through the ARRI LUT
Generator at www.arri.com/alexa/tools.
Log C material is best recorded using a 4:4:4 codec
(ProRes 4444 or DNxHD 444). The top quality 4:2:2
codecs (ProRes 422 (HQ) and DNxHD 220x) will also
provide acceptable results in Log C, but due to the
higher compression ratio, grading images recorded
with these codecs may exhibit artifacts.
• If an external recorder is used with ALEXA,
monitoring is usually hooked up to the recorder
rather than the camera, to eliminate the risk of
defective cables. The conversion therefore is
applied on the recorder’s monitoring output.
• When an HD capture system is used to record
the camera’s output in parallel, it could record
Log C and play back using a conversion LUT.
Dailies Creation
For dailies and offline edit, the Log C material needs
to be delivered in standard Rec 709 video encoding.
The camera metadata, embedded in the HD-SDI
signal and QuickTime files, lists all information
needed to select the appropriate LUT. While current