User Manual

126 Operation of the Camera
NOTICE
CAUTION! RAID redundancy is very helpful if data from one of the two internal
drives is corrupted or one of the internal drives is damaged. But the XR or SXR
Capture Drive still appears as one volume, and if it gets erased accidentally by the
user, the data is gone.
CAUTION! While this redundancy is a great new feature, it creates some
incompatibilities you should be aware of:
•
If an XR or SXR Capture Drive that has been formatted on an ALEXA SXT
should be downloaded on a Mac that does not have the ARRI RAID driver
installed, the Mac cannot recognize the RAID formatted drive and will ask if
this drive should be formatted. Don't format the drive, but install the ARRI RAID
driver and try again.
•
If an XR Capture Drive that has been formatted for ProRes on an ALEXA XT
is then placed into an ALEXA SXT, the ALEXA SXT will not be able to read the
drive and will ask if the drive should be formatted.
•
If an XR Capture Drive that has been formatted for ProRes on an ALEXA SXT
is then placed into an ALEXA XT, the ALEXA XT will only be able to see one of
the two internal drives, and will therefore also only be able to format one of the
two drives. Data may be left over on the other internal drive from the use in the
ALEXA SXT. In order to avoid this, make sure to erase XR Capture Drives by
formatting them in the ALEXA SXT or with a Mac at the end of your production.
•
Please note that due to the camera’s write pattern, there may be gaps in the
clips which do not contain valid QuickTime data. These gaps may not be bit-
identical on the individual SSDs unless the drives have previously been secure
erased using the Codex Vault. This is normal and only relevant in cases where
the date has to be restored manually.
Note: When working with ProRes clips without audio, Final Cut Pro 7 may fail during a
Consolidate action as it does not recognize the file type correctly. To fix this problem,
use the SetFile command line tool on all affected clips as follows: "SetFile -t MooV
<clipname>", where <clipname> needs to be replaced with the name of the affected
clip. Then relaunch Final Cut and redo the Consolidate action.
ARRIRAW
ARRIRAW data delivers unencrypted, uncompressed and uncompromised image
quality from an ALEXA camera. It offers the highest achievable resolution, the
camera's natural color response and great exposure latitude as uncompressed
and unprocessed sensor data. ARRIRAW images have only one channel. A color
reconstruction algorithm calculates the missing components of each pixel based on
the type and position of the array of colored filters (Bayer pattern) on the camera
sensor.
ARRIRAW de-bayering is available through the ARRIRAW SDK or custom processing,
which is implemented in most of the major post production tools for dailies processing
and mastering.
The ALEXA sensor provides a horizontal resolution of 2.8K photo cells in 16:9 and
4:3 sensor modes, and 3.4K photo cells in Open Gate sensor mode, from which down
or up-sampling routines can produce HD, 2K, 4K UHD or 4K Cine resolution images.
For VFX, the images often are processed using the native sensor pixel count and
then are up or down-sampled. Using this approach takes advantage of the luminance
resolution, which correlates to the sensor pixel count. Up-sampling ALEXA images to
4K UHD or 4K Cine works very well due to ALEXA's excellent image quality.
The following resolutions are available with ARRIRAW recording:
Sensor Mode Resolution
16:9 2.8K (2880 x 1620)