Question about EOS R C-LOG footage and MP4

[czhong]

Hello everyone. I recently bought my first full-frame camera (Canon EOS R) and I have some questions that I haven't been able to find online.

I just recorded a job in C-LOG 8 bit, but when I transfer it to my pc, it comes in mp4 format. Is it normal? I always thought that Log footage would come in a filme such as video.clog or something similar. Am I wrong? This question emerged because I was editing my flat footage on premiere and it felt like the dynamic range was short and something was off - it was when I checked and saw the footage in mp4.

Can anyone help explaining it to me?

Thank you 🙂

[John_Q]

Hello czhong,

The EOS R is only capable of recording movies in the MP4 format, so yes, this is normal. Canon Log offers a dynamic range of approximately 800% at ISO 400 or higher. Manually setting the ISO speed to 100–320 will make the dynamic range narrower.

[AtticusLake]

Log is not a video format -- it's a gamma curve.  A video format -- like MP4 -- saves pixels, which are just numbers, in a file.  The gamma curve, whether it's Rec 709 or Log or whatever, dictates what those numbers mean.

In other words, changing from Rec 709 to Log will not change the file format; it will only change how the pixels in the file are encoded.  It's up to you to decode those pixels correctly in post.  Generally, a video editor will assume that your pixels are encoded in Rec 709; normally you would add a LUT to your footage to correct it from Log to Rec 709.  You can find the official Canon LUTs for this here: www.usa.canon.com/support/p/eos-r  (look for "Canon lookup table Version 201911").

Generally you want a 3D LUT, and 65-point grid is best.  So to decode Log 3 to Rec 709, for example, you would use "3dlut\65grid-3dlut\full-to-full-range\CinemaGamut_CanonLog3-to-BT709_WideDR_65_FF_Ver.2.0.cube".

Note that to get the benefit of Log, do your exposure correction BEFORE applying the LUT.  For example, in Premiere Pro, under Effect Controls, I would add a Lumetri Colour effect to fix the exposure, and then add another one with the LUT BELOW it in the control panel.

Hope this helps.

[sketchydogllc]

What an amazing answer. Thank you so much for the detail in this reply.

[JAM713]

Actually that is incorrect. Logarithmic footage invented by Kodak with their Cineon system is indeed a format. A format is simply a way in which something is arranged. The technique involving digitizing analog film

[AtticusLake]

Well, you're quibbling about terminology.  But the MP4 file which contains Rec709 is exactly the same as the MP4 file which contains C-log3, or C-log 2, or S-log, or any other log.  The only difference is how the actual brightness levels are mapped to pixel values by the camera.

You can see this yourself very easily.  If you drop an MP4 video file on to your editing timeline, the video editor will decode the MP4 file and display the image, no problem.  But if it was shot in log, the image will be flat.  It's up to you to add a gamma curve correction, because that process is not part of the MP4 format.  That's the point I was making.

[JN2]

Thank you. Can you download Canon LUTs you listed  here: www.usa.canon.com/support/p/eos-r  (look for "Canon lookup table Version 201911") in Premiere Pro or is this for your camera?

[AtticusLake]

LUTs are a standard format.  They should work in just about any video editing software, and can even be loaded into devices, such as monitors which have LUT support.

Some cameras can also take user-loaded LUTs; but Canon cameras generally have the correct LUTs pre-loaded.  So when you turn on View Assist in a log mode, the LCD shows corrected footage.