<p>I would imagine it has something to do with the white point/primary chromaticities are Alexa Wide Gamut vs. Rec709.</p>

<p><a href="http://www.arri.com/camera/alexa/learn/log_c_and_rec_709_video" rel="nofollow">http://www.arri.com/camera/alexa/learn/log_c_and_rec_709_video</a></p>

CC BY-SA 3.0
2014-05-17T02:24:04.193Z
Welcome to Video Production on Stack Exchange.  That made an interesting read.  Also enjoyed checking out your demo reel.
AJ Henderson
CC BY-SA 3.0
2014-05-17T00:19:23.960Z
2014-05-17T00:19:23.960Z
Greg Cotten
<p>In the context of ASC-CDL, saturation is applied as:</p>

<pre><code>luma = 0.2126*iR + 0.7152*iG + 0.0722*iB
oR = luma + saturation*(iR-luma)
oG = luma + saturation*(iG-luma)
oB = luma + saturation*(iB-luma)
</code></pre>

<p>However, in the <a href="http://www.arri.com/?eID=registration&amp;file_uid=7760" rel="nofollow">ARRI Look Files in the ALEXA Camera</a> whitepaper they say:</p>

<blockquote>
  <p>Note: The ALEXA saturation parameter differs from the ASC CDL
  saturation.</p>
</blockquote>

<p>But they don't specify in what way, and I can't find that information anywhere.</p>

<p>Does anybody know?</p>

<color-correction>
How does ARRI saturation formula differ from the ASC-CDL spec?
apalopohapa
# How does ARRI saturation formula differ from the ASC-CDL spec?

(Asked by: username_0 on 2014-01-09)

In the context of ASC-CDL, saturation is applied as:
luma = 0.2126*iR + 0.7152*iG + 0.0722*iB
oR = luma + saturation*(iR-luma)
oG = luma + saturation*(iG-luma)
oB = luma + saturation*(iB-luma)

However, in the ARRI Look Files in the ALEXA Camera whitepaper they say:

Note: The ALEXA saturation parameter differs from the ASC CDL
  saturation.

But they don't specify in what way, and I can't find that information anywhere.
Does anybody know?

**Tags:** color-correction


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## 1 answers

### Answer by username_1 on 2014-05-17. Score: 2

I would imagine it has something to do with the white point/primary chromaticities are Alexa Wide Gamut vs. Rec709.

<http://www.arri.com/camera/alexa/learn/log_c_and_rec_709_video>

> **Comments:**
> **username_2**: Welcome to Video Production on Stack Exchange.  That made an interesting read.  Also enjoyed checking out your demo reel.  

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