Sony S-Log3 / Canon C-Log2 / Nikon N-Log Color Science and Midtone Overexposure Control in Right Exposure

1. Why can’t you use standard color (Rec.709) to shoot a large light ratio? Logarithmic curve (Log) essence

When recording high dynamic range scenes with a digital mirrorless camera, directly applying the in-camera standard color preset (Rec.709) only has a mere 6~8 stops of dynamic range. The bright parts are instantly pale and overexposed, and the dark parts quickly collapse into blackness:

1. Nonlinear logarithmic perception of the human eye:

• The human retina's perception of brightness is logarithmic. It is extremely sensitive to dark levels and has a dull perception of extremely bright areas.

2. Logarithmic Compression:

• Log curves (such as S-Log3, C-Log2, N-Log, V-Log) in the ADC analog-to-digital conversion stage, forcibly "flatten" the 14-15 wide light intensity signals captured by the sensor into a 10-bit data container through a mathematical logarithmic function.
• The original uncorrected Log image is gray, low-contrast, and low-saturation. It maximizes the retention of all complete original physical sampling information of extreme highlights (sky clouds) and extreme darkness (shadow details).

Two or three major mainstream cameras Log curve middle gray and white card IRE exposure standards

Blindly relying on the naked eye brightness of the LCD screen to expose the Log curve is the primary cause of full-screen color noise or highlight overflow in the later stages. You must use the in-camera Zebra or the external monitor Waveform to accurately align with the official IRE standard:

3. In-depth practical operation of ETTR - Expose to the Right

1. S-Log3’s Achilles’ heel of dark noise:

• The coding rate assigned to the S-Log3 curve in the dark area is low. If you shoot at 0.0 EV or even underexposure, when the dark area is pulled up to set the LUT in post-production, the underlying readout noise will be geometrically amplified, and the screen will be filled with disgusting red and blue noise spots.

2. Accurate overexposure +1.5 EV closed-loop operation:

• Set zebra crossing 1: Customize the camera zebra crossing to 94% ~ 97% (for highlight overexposure warning).
• Set the in-camera light meter: Manually fine-tune the aperture or shutter so that the in-camera exposure indicator meter displays +1.3 EV or +1.7 EV.
• As long as the zebra crossing does not flash wildly in a large area at the brightest sky highlight in the picture (which means the brightest point does not cross the 97% cutoff line), then all pixels of the sensor are in the best state of full charge and high signal-to-noise ratio.

3. Monitor Gamma Auxiliary Display (LUT Preview):

• Turn on "Gamma Display Assist" in-camera or load monitoring 709 3D-LUT, allowing photographers to see real-time images with normal contrast and bright colors when framing, completely getting rid of the psychological barriers to composition caused by "gray film".

4. Post-restoration workflow: color space transformation (CST) vs official 3D-LUT

1. Official Technical LUT reduction method (fastest):

• In Premiere, Final Cut Pro or clipping, import the camera's official S-Log3 to Rec.709 or C-Log2 to Rec.709 33-sided/65-sided 3D-LUT.
• Lower exposure operation: Since the exposure was +1.5 EV to the right when shooting, pull the exposure slider down -1.5 EV before the LUT node (input end) to bring the picture back to normal illumination.
• A miracle happens: all the noise in the dark areas is squeezed and converged into pure black, the picture is extremely pure and thick, and the highlight level is not lost at all.

2. DaVinci Resolve color space transformation (CST - the most professional lossless):

• Use the "Color Space Transform" tool in the DaVinci node:
• Set the input color space to Sony S-Gamut3.Cine and the input gamma to Sony S-Log3;
• Output color space is set to Rec.709 and output gamma is set to Rec.709 (or Gamma 2.4).
• Turn on white point adaptation and tone mapping to achieve smooth color transitions with absolute mathematical precision.

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