Exposure and Processing Best Practices

SONY FS7 & FS700 CAMERAS UTILIZING RAW ON THE ODYSSEY7Q+ AND ODYSSEY7Q

The Sony FS7 and FS700 output a RAW data signal that is unique to those two cameras.  It must be converted to another format in order to be processed.  Using the Odyssey7Q+ or Odyssey7Q monitor/recorders with the Odyssey RAW Bundle option,  the original RAW data can be converted to uncompressed RAW CinemaDNG files or turned into video and recorded in Apple ProRes in various resolutions and compression levels.  With the May 2015 Odyssey Firmware Update, Convergent Design has dramatically improved the color processing of the RAW data information, improving the image and particularly skin tone reproduction in both CinemaDNG and Apple ProRes formats.  There are certain particulars to each of the Sony cameras, and Convergent Design has addressed them individually. 

Sony FS700

When recording in Apple ProRes from the FS700, the RAW data must have video contrast mapping (gamma) and color information (matrix) applied to it.  This is selected using the Picture Profile menu.  Currently supported are the S-Log2 and the ITU709(800%) settings.  S-Log2 maps the full dynamic range of the camera’s sensor to the video signal and lowers the color levels so that no channel clips.  It is designed to capture the most information possible in video so that there is the greatest range of color correction available in post.  ITU709(800%) is also known as REC709(800%).  It applies a standard contrast and color level to a video signal while also turning off the knee circuit and opening up the highest levels of exposure to be fully captured in the signal without clamping.  This provides a signal that can be used as a finished product or allow for some manipulation in post.  The standard ITU709 (REC709) signal is not currently supported as Convergent Design considers the signal made available by the ITU709(800%) to be superior and capturing the greater range of the camera’s abilities.  Please note that the Picture Profile settings are not actually enabled within the FS700 but instead act only as flags for the Odyssey monitor/recorder’s image processing.  Setting within the Picture Profile menus such as Knee, Black Level and Color Mode will have no effect on the image captured by the Odyssey7Q+ or Odyssey7Q, but will alter the camera’s LCD screen as well as its HDMI output.  Settings that will alter the signal to the recorder include the ISO/Gain, Shutter, and White Balance.

Sony FS7

The FS7 has greater color controls available within it than the FS700.  To map our settings appropriately and to the look most clients prefer, Convergent Design requires that the camera’s Shooting Mode be set to Cine EI and the Color Space be set to S-Gamut3.cine/S-Log3 (Menu->System->Base Setting->Shooting Mode->Cine EI->Color Space->S-Gamut3.cine/S-Log3).  Again, these requirements pertain only to recording either RAW or Apple ProRes derived from RAW.

Exposure

Both the FS7 and FS700 have a base setting of 2000ISO when in an S-Log mode.  This is designed by Sony to give the maximum Dynamic Range of the camera’s sensor.  But it can lead to two issues in the darker portions of the signal.  While there is picture information available there, the bottom few stops of exposure can exhibit excessive noise that some may find objectionable.  In addition, the way Sony maps its RAW data signal in a linear structure.  This means that there are very few data points at the bottom range of exposure and many data points at the top of the exposure range.  This “bit-starving” of the darkest portions of the image can lead to banding artifacts in the shadows.  This effect is heightened in both cameras’ 2K mode, which limits the bit information even more.

Convergent Design recommends “re-rating” the cameras by one to two stops.  This effectively lowers the sensitivity to 500-1000ISO.  No change is made on the cameras, but the exposure is raised reaching the sensor, pushing the image data higher up the dynamic range of the sensor where there is less noise and more data bits referenced in the file.  The exposure can then be lowered in post to normalize the image, pushing any offending noise into darkness and mapping more data into the shadows to avoid banding.  While this does limit overall dynamic range, it also results in a quieter image with fewer artifacts.

Exposure Compensation LUTs

To assist in exposing images in this fashion, Convergent Design has provided two Exposure Compensation LUTs for each camera.  One is set to one-stop overexposure compensation and the other is for two-stops.  These LUTs can be used for monitoring when recording RAW or when recording Apple ProRes in an S-Log mode.  The same LUTs can then be applied in a post program such as Resolve to match what was seen while shooting.  In the future there will also be a mode for recording directly in a version of REC709(800%) with built in exposure compensation.

Convergent Design works with all out partner camera manufacturers including Sony to help clients get the most out of their camera-Odyssey combination.  We will continue to strive to achieve the best-possible images.

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Created : 2016-07-14 16:39:53, Last Modified : 2016-10-24 15:00:12

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