Davinci Resolve color management on Alexa

[Tom Evans]

I have started to look at the Davinci Resolve color management, and it looks promising. But I have noticed that setting the input color space to Alexa Log C for my source footage or applying a Alexa log to rec709 LUT actually yields quite different results. What is the reason for that? A mathematical reason I guess, but why isn't the input color space option set up to mirror the Alexa Log to Rec709 LUT perfectly as that is what is provided by the camera manufacturer? I mean, they provided this LUT because they want footage shot on Alexa to be transformed that way right?

[Amada Daro]

1 hour ago, Tom Evans said:

I have noticed that setting the input color space to Alexa Log C for my source footage or applying a Alexa log to rec709 LUT actually yields quite different results.

That is true. The LUT is made to make your footage look nice while a simple color space transform is made to take your footage from one color space to another non-destructively. Look at the curves below to see the difference.

[Alfonso Merino]

Have you tried luminance mapping? 

[Amada Daro]

Luminance mapping bends the top end of the curve.

[Alfonso Merino]

The ARRI LUT does that too... But if Tom wants to get a closer result to the LUT with RCM that's a way. First pic is ARRI LUT and 2nd RCM

 

 

Edited March 3, 2018 by Alfonso Merino

[Alfonso Merino]

2 hours ago, Alfonso Merino said:

Have you tried luminance mapping? 

I meant the "Tone Mapping" in Resolve, 

Edited March 3, 2018 by Alfonso Merino

[Paul Dore]

This plugin has the option of a technical LogC Alexa Wide Gamut to Rec.709 transform, but with the additional ability to roll off the highlights into display space.