C100: AVCHD vs Pro Res 422 HD for Color Correcting

JoeJITSU

JoeJITSU

Veteran
I heard that the 422 ProRes is suppose to be better for Color Correcting. I tested it on C-Log and after looking at my Footage and comparison here..Looks the same to me. I copied the same color correction & FilmConvert Pro settings from the ProRes Clip and it looks identical, unless I am not seeing something you guys are.


PassWord is DVX
 
Just to be clear: are you comparing footage captured externally to ProRes 422 with clips form an internal AVCHD capture? I just want to rule out that you are using the same AVCHD source clips and only using the ProRes 422 as an intermediate…

Anyway. The difference between ProRes 422 and internal AVCHD is pretty minute. ProRes will resolve fine detail a little bit better, but might also be a wee bit noisier due to less smearing.

An external ProRes 422 file will no doubt be much "richer". Higher bitrates and 422 color space allows for that. The whole point of AVCHD is that it WILL basically look the same as a ProRes coming out of the camera. It's the whole point and it works pretty well. It's very efficient.

The kind of light grade that you are doing won't be problematic for AVCHD. But let's say that you want to shift hues around or push luminosity values more than just a nudge... Or if you do secondary color grading, isolating certain areas of the image... That's where you might see more of a difference.

Alas, here is where we face the next problem with most Canon cameras: the 8 bit codec. Even if you record to "10 bit ProRes" externally, the camera is only giving away 8 bits worth of discreet values, so you are still left with the original 8 bits worth of actual data.

But to sum it up: if the comparison above is representative of your normal workflow, you don't need anything other than AVCHD.
 
you'll see the difference when you have lots of red colour in your scene, flesh tone for example, qualification is relatively cleaner with 422 colour sampling
 
AndreeOnline said:
Just to be clear: are you comparing footage captured externally to ProRes 422 with clips form an internal AVCHD capture? I just want to rule out that you are using the same AVCHD source clips and only using the ProRes 422 as an intermediate…

Anyway. The difference between ProRes 422 and internal AVCHD is pretty minute. ProRes will resolve fine detail a little bit better, but might also be a wee bit noisier due to less smearing.

An external ProRes 422 file will no doubt be much "richer". Higher bitrates and 422 color space allows for that. The whole point of AVCHD is that it WILL basically look the same as a ProRes coming out of the camera. It's the whole point and it works pretty well. It's very efficient.

The kind of light grade that you are doing won't be problematic for AVCHD. But let's say that you want to shift hues around or push luminosity values more than just a nudge... Or if you do secondary color grading, isolating certain areas of the image... That's where you might see more of a difference.

Alas, here is where we face the next problem with most Canon cameras: the 8 bit codec. Even if you record to "10 bit ProRes" externally, the camera is only giving away 8 bits worth of discreet values, so you are still left with the original 8 bits worth of actual data.

But to sum it up: if the comparison above is representative of your normal workflow, you don't need anything other than AVCHD.
Click to expand...

+1 on Andree's comments, especially the first caveat - if you're just transcoding from AVCHD to ProRes, you won't notice any difference. But I'll leave that for you to clarify.

In my experience, when looking at ungraded material, there's one small area of the signal that does tangibly benefit from the higher bitrate encoding - and that's on reds and the transition from red within the picture. Have a look here:

http://www.dvxuser.com/V6/showthread.php?320327-New-Atomos-Ninja-Blade-With-HDMI/page18

I posted the pics for different purposes (Ninja Blade firmware 5.1 blanking issues), but they do also show where the C100 AVCHD encoding struggles with transitions to and from red within the picture.

I'm not a huge believer in ProRes/high bitrate intra frame acquisition for web delivery, but I was caught out on a recent interview, where a distant red neon sign in the background broke up noticeably. We bought the Ninja Blade mainly for it's monitoring - but it has also resolved the "red issue."

Ben.
 
See this test from cca 8min:
https://vimeo.com/88598926

The first is AVCHD, the second is AVCHD transcoded to DNxHD185 (the same as ProRes HQ 422), the third is Ninja2 recording (DNxHD185 422 8bit), the fourth is avchd again (for direct comparison with the third).

The red issue is nice visible on the color table at PIP (magn. 400pct).
 
cpreston - for me was interesting that internal C100 NR works also with the external recording. It is less visible for the first looking but really clear visible in a detailed view (it is the best to download the orig file). The NR2 makes the external recording less noisier. I want Ninja Star recorder (weight 100g) which helps a lot with high isos or with quick move recording.
 
The ProRes is straight out of my Ninja 2.
My son who is a Videographer for A&E pointed out the Blues looked a little different in the sky and the clouds looked different. I guess he has better eyes than me. He also said that the ProRes coming out the Ninja is not a true 10 bit rate? Not sure what he means
 
JoeJITSU said:
The ProRes is straight out of my Ninja 2.
My son who is a Videographer for A&E pointed out the Blues looked a little different in the sky and the clouds looked different. I guess he has better eyes than me. He also said that the ProRes coming out the Ninja is not a true 10 bit rate? Not sure what he means
Click to expand...
The C100 HDMI out is 8 bit so it stays 8bit even if the recorder is set to 10 bit. it will record a 8 bit signal in 10 bit with no benefit.
Atomos seems to think recording that recording an 8 bit signal is better when using a 10 bit setting, and that makes no sense. If it did then we wouldn't need 10 bit output from cameras. Right?
 
Erik Naso said:
... ..it will record a 8 bit signal in 10 bit with no benefit.
Atomos seems to think recording that recording an 8 bit signal is better when using a 10 bit setting, and that makes no sense. If it did then we wouldn't need 10 bit output from cameras. Right?
Click to expand...

JoeJITSU said:
...He also said that the ProRes coming out the Ninja is not a true 10 bit rate? Not sure what he means
Click to expand...

If you have original clip (internal 420 colors AVCHD with Group of Pictures - GOP) then there is no benefit.

But if you record externally 422 colors ("I-frame only" which means that every single frame is compressed independently)
then there is a very small difference in file size for 8bit vs. 10bit scale (256 shades vs 1023 shades), rescaling to fine 10bit can help to maintain the quality in postproduction, but cannot add anything else than was at original clip. So 10bit recording (in the case of 422 colors) doesn't matter to anything.
From HDMI output (422 colors 8bit uncompressed) you get false 10bit (re)scale, but true 422 colors. It is a good start point for the postproduction work.
 
for me a good example not worrying bout my internal C100's internal recording. The compression algorythm of the c100 is top notch.
 
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