In a previous tutorial we looked at the Technicolor CineStyle profile for Canon EOS DSLRs, which enables a logarithmic curve in EOS footage to increase dynamic range and detail and provide greater latitude in grading.
- Logarithmic Curves for Your Canon DSLR: Technicolor CineStyle for Canon EOS and Magic Bullet LUT Buddy, by Ned Soltz, DV.com, September 26, 2011
Rear connections on the Sony PMW-F3 camera
Sony PMW-F3 users can unlock the S-Log feature in their camera with the CBK-RGB01 software key ($4,400 list), which enables 3G-SDI output, Dual Link RGB444 video output and various LUTs in addition to S-Log gamma settings. We will look at the principle behind S-Log, its application, and a quick step-by-step guide.
The Sony F3 uses a 16-bit sensor sending out a 10-bit signal. While it records internally to the 8-bit XDCAM EX codec, it can output 10-bit 4:2:2 YUV or 10-bit 4:4:4 RGB (with the CBK-RGB01 unlock key). The standard HD Rec. 709 color space with the F3’s cine gammas will produce a dynamic range of about 11 to 11.5 stops. The S-Log processing effectively places the entire processing capability of the 16-bit sensor into the 10-bit stream to yield a dynamic range of 13 to 13.5 stops. The result is greater detail and a far greater latitude. The S-Log option makes the PMW-F3 an entirely different camera!
Dual Link & Gamma Select menu
The image itself will appear flat, but grading in post will bring out more detail than grading Rec. 709 footage because the S-Log material has greater range and more information. If you wish to visualize how certain ranges applied to the footage will appear, then use any of the built-in LUTs (lookup tables) in camera. The LUT is only a representation for visualizing the image, not a final output product. This is important to understand.
In firmware version 1.2 (release notes PDF), Sony enabled the use of EI (exposure index) settings equivalent to ISO 800-3200. Note that applying these EI changes affects only the appearance of the LUT. The purpose is to visualize how far you can “push” the image. Think of the old days of film when you could “push” your ISO 100 film to maybe 400.
A 10-Step Guide to S-Log
- Install the CBK-RGB01 according to the directions that come with your card.
- Determine whether you will be recording 4:4:4 RGB 1.5 or 3G RGB or 4:2:2 YUV, depending on your recording device.
- You can record 4:4:4 RGB only to a device that accepts Dual Link or 3G—at the moment, that list includes the Sony SR-R1 HDCAM SR solid-state recorder, Convergent Design Gemini 444 and Cinedeck—or directly into your NLE via a capture card that supports Dual Link or 3G HD-SDI.
- If recording Dual Link/3G, set the Video Set -> Dual Link & Gamma Select menu to 1.5G or 3G RGB444 & S-Log (depending on your device). Set the SDI/HDMI menu to SDI or HDMI, depending on how you are monitoring. You can view the LUT output only via the HD-SDI or HDMI outputs. Turn on the S-Log LUT option, select a LUT and optionally apply an EI (Exposure Index) to give yourself an idea of how much range you have in the shot, both to protect your highlights and preserve shadow detail. The EI only shifts the dynamic range up or down.
- If recording to an eternal 4:2:2 device, set the Dual Link menu for 1.5G RGB444 & S-Log, and the HD-SDI mode for HD-SDI or HDMI. You cannot select both. In this configuration, the LUT will be output through the SDI or HDMI ports, meaning that turning on the LUT will actually record it. Thus, to avoid recording the LUTed output, turn off the LUT. Firmware version 1.3 will allow the use of 4:2:2 signals from the A port of the Dual Link, preserving the ability to view LUTed material through the HDMI or SDI ports.
- In S-Log, white balance can be preset only to 3,200°K or 5,600°K. There is no manual or auto white balance. White balance can be adjusted in picture profile with the 1.2 camera firmware. Also, all Picture Profiles are turned off.
- Exposure is best set using a waveform monitor, but even without a WFM you can set exposure using either a monitor with false color or the percentage indicator in the F3 viewfinder, which will be close to the IRE measurement on the WFM. One rule of thumb that I use is to make a test exposure for the scene by exposing a gray card around 35 percent. I will keep skin highlights in the 40 to 45 percent range. I certainly do not want to exceed 50 percent. When I use my Zacuto viewfinder, which displays false color, I err on the side of underexposed, mostly to protect my highlights.
- Transfer footage to your favorite NLE or grading application. Whether using color wheels or curves, I like to set my contrast first. Then adjust gamma. Raise or lower your highlights as desired. Add saturation. Correct colors as needed. Then tweak to establish your desired look.
- You can also use a plug-in (in my case, for Apple Final Cut Pro 7) from Pomfort Software called SLog2Video. It will apply a Rec. 709 gamma curve to S-Log video as a starting point for grading.
- S-Log will also be recorded to internal SxS cards and, if LUT is turned on, the LUTed image will be recorded. This will be most useful when firmware 1.3 is released, which will allow 4:2:2 recording via the A port, leaving the SDI/HDMI ports for LUTed output, if desired.
S-Log LUT Select menu