topic Re: C200 XF-AVC C-Log 3 Different from CRM C-Log 3 in Professional Video

C200 XF-AVC C-Log 3 Different from CRM C-Log 3

Hale — Thu, 10 May 2018 03:31:10 GMT

Hey everyone, new user here.

So I've been working with the C200b since December. When the new XF-AVC format was included in the latest firmware, I was finally freed of the painful MP4 proxy workflow.

Unfortunately, I'm having trouble figuring out what gamma curve the XF-AVC proxies are using. Normally, the MP4 proxies use a BT.709 color space and Canon Log 3 Gamma curve. This is useful because I most often edit the CRM files starting with Canon Log 3, and only resort to the more aggressive Canon Log 2 for pulling out some detail in the shadows.

Here are some examples:

As you can see the Canon RAW Light has that classic Canon Log 3 Gamma curve, with the smooth roll off into shadows. The XF-AVC looks more like a Wide DR Gamma curve with how much contrast is baked right into the image. I've compared it to the Wide DR gamma curve and they are considerably different.

TL;DR: Does anyone know the gamma curve that the XF-AVC proxies record in? Is there a way to change that?

Thanks!

Re: C200 XF-AVC C-Log 3 Different from CRM C-Log 3

Tim — Fri, 11 May 2018 22:59:45 GMT

Hello Hale,

If you have the camera set to Canon Log Gamma 3 on your main recording, then the gamma curve for the proxy should also be Canon Log Gamma 3. The camera may be set to a different Color Matrix though for the proxy which would explain the disparity. You should check right under Canon Log Gamma in the Menu and ensure that your Color Matrix is set for Neutral. It almost looks like the bottom proxy photo looks like the EOS Cinema Standard Color Matrix instead of Neutral.

Do you have the camera set so that it's in the Gamma Log 3 Gamma Preset- or are do you have the Preset set to OFF?

Re: C200 XF-AVC C-Log 3 Different from CRM C-Log 3

Hale — Sat, 12 May 2018 19:42:45 GMT

Hey Tim,

Thanks for the prompt response! I took a look at the menus to get a grasp on what is going on. The short story: I can't seem to get the Gamma curves to be the same for CRM and XF-AVC files. Here is what I found...

Here is the comparison when the preset is on Canon Log 3:

The histogram shows how the XF-AVC has more contrast than the Cinema RAW Light, despite the preset being set to Canon Log 3.

The same goes with when the preset is OFF:

The Gamma is set to Canon Log 3, and the Color matrix is set to Neutral. Still though, the gamma curve does not match.

Now to confirm, the MP4 proxies behave differently. Their gamma curve is far more similar to the Canon Log 3 gamma curve.

The colors differ slightly, but the gamma curve is almost identical.

Sorry for the image spam. Here is a google drive folder with the full size comparison images:

XFAVC Example Images

I will check to see if the problem lies within premiere, as that is one area I haven't checked yet, but from what I can tell so far the XF-AVC just has a different gamma curve regardless of what gamma curve you set.

Re: C200 XF-AVC C-Log 3 Different from CRM C-Log 3

GeneHermit — Wed, 10 Nov 2021 21:02:36 GMT

I am having the same experience. Did you ever get a satisfactory answer or find a solution or acceptable workaround?