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🎬HDR

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Linear isn’t really 1:1 if it’s increasing according to stops (a log scale)

With linear recording, your brightest stop contains as much information as the entire rest of the picture

The problem arises with the realization that the exposure values with which we measure light are not linear. An exposure “stop” represents a doubling or halving of the actual light level, not an increase by some arbitrary linear value on a scale. You could, in fact, say exposure values are themselves logarithmic!

So, working backward, using the camera example: in a linear recording, the voltages coming from each pixel off the camera’s sensor are assigned one of those 256 values, based on voltage level, which is determined by the actual exposure level of the image focused by the lens. Now, since exposure values are logarithmic, the voltage levels being output by the sensor to the A/D converter reflect that. And when those voltages arrive at the A/D converter, it records them using a linear function. The downside is that this method top-loads the 256 values, and the dynamic range won’t be equally represented across the 8 bits. 

S-Log is recorded using data range, but black is put at approx 10 bit CV92 – 8 bit CV23 to retain compatibility with other film log curves. S-log2 goes up to the equivalent 104 IRE . S-Log2 has only approx 225 code values and S-Log3 a measly approx 195 code values. However both curves with the right camera could reach 109% or CV1024/255.

Typically if you are shooting with 8 bit, for example with an FS5 in UHD or an A7S, A7R etc, then I recommend you use S-Log2 with SGamut. For most other cameras that have 10 bit recording then I recommend S-Log3 and SGamut3.cine.

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