topic Re: Canon C200 proper exposure in raw, ire level for middle grey 18% in Professional Video

Canon C200 proper exposure in RAW with WFM, Proper IRE for 18% gray

yvesbernas — Mon, 07 Aug 2023 16:34:47 GMT

Concerns: Canon C200 proper exposure in RAW with WFM

Some DOPs like Rubidium say: expose an 18% gray card at 42IRE when preset at C-log3 because this is what the canon papers recommend for C-Log2 and since RAW is recorded in C-Log2 in this camera, the IRE should be at 42 . (Cinematographer Ben Schubert also recommends 42 IRE but does not specify the preset !).

I have my doubts on all this because IRE values on the waveform monitor depend on the preset : C-Log3, C-Log, Rec709 or “OFF“.

Since there is no preset C-Log2 on the C200, you cannot use the recommended value of 42 IRE, you should use the recommended mid grey level value for the chosen preset.

On a graph published by CANON showing curves for “10 bit code value” versus “Relative stop from 18% grey” for BT709, C-Log, C-Log2 and C-Log3 (see pic below), you can read the 10bit code value for a zero deviation from 18%grey (middle bold vertical axis, which is the 10bit code value value for an 18% grey) and convert it to IRE. This yield approximately 35 IRE for C-Log3, and 44 IRE for BT709 (and 42 for C-Log2).

So my guess is that if you preset to Rec709, you set the exposure so that the 18%grey card shows 44 IRE on the waveform monitor.

Or if you preset C-Log3, the IRE should be 35 (and not 42 like Rubidium says. Ben Schubert does not specify the preset for his recommended 42 IRE ).

Am I correct or did I miss something ?

Canon C200 proper exposure in raw, ire level for middle grey 18%

yvesbernas — Mon, 07 Aug 2023 16:18:49 GMT

Concerns: Canon C200 proper exposure in RAW with WFM

I have my doubts on all this because IRE values on the waveform monitor depend on the preset : C-Log3, C-Log, Rec709 or “OFF“.

Since there is no preset C-Log2 on the C200, you cannot use the recommended value of 42 IRE, you should use the recommended mid grey level value for the chosen preset.

On a graph published by CANON showing curves for “10 bit code value” versus “Relative stop from 18% grey” for BT709, C-Log, C-Log2 and C-Log3, you can read the 10bit code value for a zero deviation from 18%grey (middle bold vertical axis, which is the 10bit code value value for an 18% grey) and convert it to IRE. This yield approximately 35 IRE for C-Log3, and 44 IRE for BT709 (and 42 for C-Log2).

So my guess is that if you preset to Rec709, you set the exposure so that the18%grey card shows 44 IRE on the waveform monitor.

Or if you preset C-Log3, the IRE should be 35 (and not 42 like Rubidium says. Ben Schubert does not specify the preset for his recommended 42 IRE ).

Am I correct or did I miss something ?

Re: Canon C200 proper exposure in raw, ire level for middle grey 18%

Anonymous — Mon, 07 Aug 2023 16:24:10 GMT

Perhaps you should post this question to the Video section.

Re: Canon C200 proper exposure in raw, ire level for middle grey 18%

yvesbernas — Mon, 07 Aug 2023 20:15:03 GMT

Yes, thanks.

Re: Canon C200 proper exposure in RAW with WFM, Proper IRE for 18% gray

John_Q — Wed, 09 Aug 2023 21:41:30 GMT

Hello yvesbernas,

Based on the chart and information provided by Canon, I would agree with your assessment.