C100: C100: Post Converted AVCHD vs External Recorders

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absolutmp5

New member
Hey Guys,

I have the C100 and now the Ninja Star. I use to use the internal AVCHD and then convert to Prores HQ via FCPX ingestion process. With the Ninja Star shooting in ProRes HQ, I figured I would get alot more out of the post color correction process. However when actually working with both variant's of the footage Im not noticing any distinguishable differences. Does anyone come to similar conclusions? if not, can anyone tell me why it would be a good idea to keep the recorder? Thanks again.


Kris
 
absolutmp5 said:
Hey Guys,

I have the C100 and now the Ninja Star. I use to use the internal AVCHD and then convert to Prores HQ via FCPX ingestion process. With the Ninja Star shooting in ProRes HQ, I figured I would get alot more out of the post color correction process. However when actually working with both variant's of the footage Im not noticing any distinguishable differences. Does anyone come to similar conclusions? if not, can anyone tell me why it would be a good idea to keep the recorder? Thanks again.


Kris
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The AVCHD codec is really strong. I have seen it fall apart badly with deep focus foliage during dolly moves... "dancing" light projected through water onto a high contrast moving scene... super high ISO a bit... but it is pretty much awesome. I have used it when my Ninja was down or I wanted a smaller rig and it always comes through, but if you zoom in really far you can see the slight difference. If you're shooting for theatrical exhibition I think you might have problems with apparent macro blocking occasionally, but for tv or web content no way. Canon wasn't trying to sell an unusable camera...

That said I like the image from the recorder. The AVCHD is great 90% of the time, it's great 100% of the time (when it works).

Fire can be tricky, too. Shoot a deep focus scene panning through fine branches on both the recorder and AVCHD and zoom in to 400% and the difference should be immediately apparent.
 
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AVCHD is what kept me from buying the C100 - until I used one. I shoot handheld mostly, with an EVF, so an external recorder is out (I need the camera's info on screen, WB, iris etc) and I like to know it's actually recording after I push the button. I was worried about AVC for about 60 seconds. After a year of shooting hundreds of hours of footage I've never had a single shot that cried "Oh My God!" Sure, some stuff in forests etc might be better, as policar says above, but unless the shows boring and the audience is losing interest, no one notices. Oh, BTW, I make documentaries often for broadcast: When asked about codecs, I've adopted a don't ask, don't tell policy.
 
I hear a lot about how the uncompressed out helps with color correction, but I've never seen an example Does anybody have a comparative video of either pulling a key or selective color correction or secondaries that might show the benefit of external vs internal for heavy grading?
 
If your having a hard time seeing the difference then its most likely because you aren't pushing the footage enough. The internal avchd works GREAT when there is enough light, but there are a few scenarios where the external 4:2:2 has a big advantage. My advice would be to run a couple of small tests such as these:

1. Shoot a scene with the wrong(or even marginally off) white balance and adjust it in post
2. underexpose a shot and try to lift the shadows in post
3. change the white balance on skin tones
4: shoot 60i slow it down in post, color grade
5: shoot green screen and try to pull a clean key
6: try rotoscoping a moving or inanimate object

In each of the above instances you will notice the internal footage either falls apart or is exponentially more difficult to work with.
 
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Leo's list is pretty comprehensive.

I'd strongly 'Second' the Chromakey point if you're not using FCPX's built-in keyer. I've been beaten up about this but I don't care: the FCPX keyer isn't particularly strong with 'good' master material, other keyers give better results when you do it 4:2:2 and 'do it right'.

The internal AVCHD recordings include noise reduction. The 4:2:2 output does not - on the default CPs anyway. I'm working on a little test for this, but in general, the externally recorded material does not have Noise Reduction, and if you're not careful, or choose a low bandwidth version of ProRes with gain added, you can get a worse result than AVCHD.

OTOH, scenes with strong coloured lighting, intense reds, and high detail/high action (especially with a bit of gain) do benefit from being recorded at ProRes 4:2:2 HQ.

You are getting more info on the ProRes recordings, but you're not going to spot much of this on the web. Where you WILL see it is when your image is 'writ large upon the screen' - there are some ugly artifacts in AVCHD that final compression to H.264 hides, but playback in ProRes does not..
 
MattDavis said:
Leo's list is pretty comprehensive.The internal AVCHD recordings include noise reduction. The 4:2:2 output does not - on the default CPs anyway. I'm working on a little test for this, but in general, the externally recorded material does not have Noise Reduction, and if you're not careful, or choose a low bandwidth version of ProRes with gain added, you can get a worse result than AVCHD.
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Wasn't this disproven?

Otherwise, I agree. Unless you are keying or have high stress image characteristics of some sort... or shooting for theatrical release (not a festival short, but something with guaranteed theatrical exhibition) the only reason to use a prores recorder (the main one in the first place, really) is to save time and not have to transcode. The AVCHD is fine.
 
MattDavis said:
...The internal AVCHD recordings include noise reduction. The 4:2:2 output does not - on the default CPs anyway. I'm working on a little test for this, but in general, the externally recorded material does not have Noise Reduction, and if you're not careful, or choose a low bandwidth version of ProRes with gain added, you can get a worse result than AVCHD.
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Interesting, on my C100 the NR works also for 422 HDMI output, it is a clean visible. Download the orig file and look at for noise in black - https://vimeo.com/88598926 (start from 10:00 for ISO2000 part). The video is also a good answer for the question about an external recorder, with internal NR2-3 you will get very nice signal on the 422 output, much better noise in the three sequenced frames (look for any three frames from the internal AVCHD in black parts with higher iso).

The external recorder Ninja2 with the internal NR (NR0, NR2, NR4), at the name is time from the video:

http://www.videoproduce.cz/images/006b_NINJA2_NR0_at_21min_30sec_origQT.tif
http://www.videoproduce.cz/images/007b_NINJA2_NR2_at_22min_07sec_origQT.tif
http://www.videoproduce.cz/images/008b_NINJA2_NR4_at_22min_40sec_origQT.tif
 
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Thanks Matt, but if you look for tif pictures from DNxHD185 (Mbps), you will see that internal NR really works for external output.

I hope this helps :-) .
 
You don't need another one? Saints preserve us, so much for the scientific method and peer review. LOL

Folks, my test is different. It moves. Well, the noise does. LOL - Seriously, check it out. Not now, whenever. It wasn't actually an official test either, I was trying to get the recorder to trigger over HDMI, and noticed the rather glaring issue and did a bit more playing around. Pave1, you'll have to take my word for it until you see it.
 
MattDavis said:
You don't need another one? Saints preserve us, so much for the scientific method and peer review. LOL

Folks, my test is different. It moves. Well, the noise does. LOL - Seriously, check it out. Not now, whenever. It wasn't actually an official test either, I was trying to get the recorder to trigger over HDMI, and noticed the rather glaring issue and did a bit more playing around. Pave1, you'll have to take my word for it until you see it.
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What were your NR settings? Just curious.

No matter how much I boost the signal on your video, I agree with Pave1. Yes there is slightly less noise in your video in the AVCHD clip than in the ProRes clips when in motion, because the codec preserves noise poorly (it's the single most difficult thing to compress) and either smooths it out or because it's interframe the noise carries over through the GOP.

It's a useful example of how good AVCHD is, about on par with ProRes422 nearly as good as ProRes HQ it looks like for this shot. But if you look at the character of the noise in AVCHD you can almost see it flicker with the GOP and see artifacts carry over between frames, other bits smooth out a bit. Otherwise the levels are the same.

This is a codec issue, the NR is the same on every clip.
 
Matt, my english isn't so good, sorry. My test is OK.

AVCHD has (at sequence of three frames) one frame /I/ with noise and two frames /BP.../ with more compression artefacts. The external recorder has on these three frames the same type of information - the same type of noise (no artefacts).

This can look (with internal NR) that in AVCHD has NR much more visible "effects", but it is not true. IN clean noise is the NR less visible, but works.
See this tiff from video (see "one color" faces on 400pct PIP), you will see that.

I hope that you understand what I mean, all the best for you and your work!

Pavel
 
Policar said:
What were your NR settings? Just curious.
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Will have to get back to you on that - buried in edit suite away from gear.

Policar said:
But if you look at the character of the noise you can almost see it flicker with the GOP. This is a codec issue, the NR is the same on every clip.
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This was my point about using ProRes HQ on a recorder when the noise of the C100 swamped the ProRes422 codec. I see a tighter defined noise on the 422HQ, I see the 'smears' below that on the iFrame codecs.
 
I agree with both you and Pave1 regarding the character of the noise, but I think it's due to the codec not due to NR being disabled via HDMI.

I have seen this when lifting black levels and it is very annoying. Certainly the lack of this artifact is a benefit of using prores in dark scenes.
 
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