Canon C100 - Internal Codec vs Prores External

[Dave Mercer]

I've been loving my C100 for the past 8 months, shooting for international broadcast news. The C100 is a joy to use, and helps me keep a low profile.

I've spent the past week filming a doc for international broadcast. The channel requires 50Mbps at a minimum, so the producer picked up a C100 and Atmos Ninja.

I find the Ninja with one big battery mounted on the rear part of handle upsets the balance a fair bit, and adds to the weight. Almost all of the filming is handheld, and my back aches!

More upsetting, one of the HDDs died after filming the other night and I was only able to rescue the short clips (using the fantastic Data Rescue). We have backups on the SDHC cards, but still it is a pain.

With the issue with the Ninja, I guess I wanted to know what the difference in quality between the Prores files and the AVCHD files will be. I'm having difficulty seeing a difference, but I'm not viewing on a professional monitor. If there's only light grading going on, will an engineer see the difference? After going to broadcast (with the various compressions to get it there) will the difference in the AVCHD and Prores clips be noticeable?

Thanks.

PS - I find it difficult to understand how a news channel that has aired docs filmed on HDV can demand 50 Mbps ... I mean, this ain't a half million dollar discovery production ...

[Barry Goyette]

The biggest difference will be in the level of compression artifacting. Specifically, if you blow up the the avchd footage to 200 or 400% you'll see the typical image compression you might see on a highly compressed jpeg. The ProRes version will show a film-like grain. I've noticed that large, flat mid shadow tones will tend to crawl or vibrate somewhat on internally recorded footage where as the pro-res is much more stable looking.

For footage that isn't going to be graded much, there is very little difference in the final output, but if you're shooting c-log and grading, you will see a substantial improvement in the noise characteristics with a recorder (mostly when shooting gained-up in low-light situations). Others have reported much better results when keying with recorder footage versus recording to a card. C100/c300 footage is remarkably film like in it's grain structure when run through a recorder, and will do better I think in 4k display and theatrical exhibition.Otherwise, in terms of color, dynamic range and gradation, you won't see much if any difference between the two, even when grading.

Barry

[Dave Mercer]

Thanks very much for the explanation Barry. Minimal grading will be done, so hopefully the loss of the Prores files won't be too obvious.

I'm doubting the editors at the channel are going to blow up the footage 4x to look for compression artifacts. I guess I was worried that putting the doc through the delivery to transmission chain would cause the AVCHD to fall apart much more than the Prores clips.

[Barry Goyette]

Lot's of people just simply convert everything to ProRes after the fact, as it's a better editing format anyway...if you're concerned about problems upstream...then that's the way to control things. It won't miraculously improve the footage, but the client will be happy to receive it that way.

Barry

[Al Bergstein]

Barry is right on all counts. And transcoding to Prores after the fact is likely to be the best way to solve the problem. The viewers of the footage on broadcast are unlikely to see the difference, as I've just completed my first few commercial videos on my C100 (they are all behind password protection at the moment due to marketing issues needing to get resolved by the clients), and it plays quite well on my 42" Sony Monitor. Any issues are my fault and would have happened on a 4:2;2 camera too... (like a bit too contrasty at times).

Frankly, for all the hassle that people seem to be having with external things like the Ninja (yes, many people don't have problems, but from what i've been reading, you are not unique), it seems better when shooting for broadcast to simply either shoot on an XF305 or C300 (or go to Sony) and get the 4:2:2 without the hassle.

My xf305 does 80% or more of my C100, some things better, but when the C100 is in it's sweet spot (shallow DOF especially in close quarters, or low light situations) it is much better. Maybe by next year I'll just bite the bullet and get the C300. Best of both worlds. Twice the price (sigh)...

[Ben Giles]

The 50 Mbps minimum exists for reasons beyond what you, I or a top tech engineer with million dollar eyesight can see. It comes down to the behaviour of crap multiplex digital TV broadcast systems (actually, they're quite clever - but the result often looks crap.)

DSLRs (except the EBU-approved 1DC) suffer from aliasing artefacts and AVCHD has other noise and 4:2:0 artefacts - many of which you often won't notice even on the nicest grading monitors - which pass very cleanly through the broadcast chain. These errors cause damage to the output (ie a punter's TV at home) and can affect other channels in a multiplex by chewing up all the available bits. From the head of BBC HD in a conversation about DSLRs and sub-50 Meg codecs last week (edited by me for clarity):

"(These) cause issues that you can't see in the edit or grade but will damage the encoded output... It does however affect the quality of each encode so quality drops every time you pass though baseband. Remember the emission encoder is the most aggressive part of the chain and it's head room is limited by the maximum processing power of the consumer set top box and how busy all the other channels in the multiplex are... This also affects the quality of the SD channels too as the extra unwanted signal looks like high detail and therefore the encoders believe it important to encode it at the expense of lower resolution parts of the signal (i.e. detail in the black or solid blocks of colour)."

By the way, by baseband he means each time the master file is passed from one system to another - that might be taking your ProRes master file to a grading suite, ingesting it into the playout server etc etc - in each case, the system will do a fresh encode, decompressing it to baseband (uncompressed) and recompressing it back to whatever codec you're using.

So, you can supply AVCHD-transcoded to ProRes material and the chances are nobody will actually notice. But if they audit your stuff and demand the original rushes, you might kiss goodbye to your broadcast career - especially if you put a production company's cock on the block by doing so.

The C300 exists really to tick this box in a neat, robust and manageable package (unlike a Ninja combo which is fraught with risk) - and it's why Canon can totally take the piss with the pricing of it, compared to the C100 (my opinion, of course.)

Most of my work nowadays is non-broadcast BBC web-based material - so the C100's native AVCHD works brilliantly for me. When we supply stuff for broadcast, we rent a C300 or Alexa. Personally, I think the XF camera pics look very low rent - even if they do tick the "broadcast spec" box. But I guess they work in a no-fuss get-on-with-it shooting scenario.

Wouldn't it be great if the next iteration of the C100 had an extra purchase option of a bolt-on and therefore ergonomic and robust 50+Mbps factory recorder? (like wot Sony does.)

Ben.

[Matt Davis]

Firstly - Ben <--- Word! +1

Originally Posted by Dave Mercer

I guess I wanted to know what the difference in quality between the Prores files and the AVCHD files will be. I'm having difficulty seeing a difference, but I'm not viewing on a professional monitor. If there's only light grading going on, will an engineer see the difference?

For talking heads, 'not a lot' to the eye, but the vectorscope will look like a teabag - lots of little perforations letting the colour out. But things can get nasty with reds and motion. Engineers will spot it via the vectorscope.

Tip o' the hat to Chris Meyer over in the 'other' forum who may have solved my red-on-AVCHD issue as an FCPX anomaly, strengthening my reliance on 5DtoRGB converting C100 AVCHD to ProRes when I have the time/budget. But to ProRes - apologies to all who have seen this all before:

4:2:2 vs 4:2:0 on the C100 <-- easy test
4:2:2 vs 4:2:0 <-- not quite so relevent, but shows the vectorscope thing
AVCHD Killed by a tree © Matt Davis 2013 <-- why you need to think about ProRes for high motion

and...

C100 noise and its effect on ProRes on Vimeo

I have found (but some have told me that I am obsessing) that low IRE, low detail areas can have a certain amount of 'boil' in the naturally textured 8-bit C100 image and whilst the inbuilt noise reduction of the C100 tames it on the internal AVCHD recording, the super-clean HDMI output has no such noise reduction and this can swamp the standard ProRes 422 codec - it needs the 422HQ version to capture the natural texture of the C100.

This mirrors tests done a while back with the Sony PMW-EX1R. The general consensus being that you're not going to have your socks blown off by the difference between the internal recording and the HDMI/SDI capture on an 8 bit camera until things get active/detailed and you record in HQ.

As for Chromakey, well - I've had very good results with AVCHD just as a simple background replacement using hybrid chroma keyers (e.g. Keylight, FCPX), but if you need difficult edges, translucency/reflections, difficult fabrics (white), get 4:2:2. And maybe a different camera (10 bit at least). And if you want to do motion match, watch out for rolling shutter. The cost of working with a camera that has a global shutter will work out cheaper than trying to fix it in post.

Originally Posted by Dave Mercer

I find it difficult to understand how a news channel that has aired docs filmed on HDV can demand 50 Mbps ... I mean, this ain't a half million dollar discovery production ...

Broadcast news is generally very happy with 35 Mbit XDCAM, despite the 422/50 mantra.

'The Family Who Walked On All Fours' is a famous multi-million earning, award winning documentary filmed on a couple of Z1s and edited in Final Cut on laptops in a barely converted lean-to garage in the countryside. However, i) the pair who made it are just brilliant, know EXACTLY what they're doing, and the film was so compelling - who cares about what the vectorscope looks like?

(BTW - in the analogue days, video with bad highlights or colour could blow up the transmitter - hence the 'legalisation' process, but I digress)

If you shoot the most amazing stuff on an iPhone, stuff that huge swathes of the population want to watch and which gathers advertisers who wish to share some eyeball room from that audience, you're going to be broadcast - even shown on the big screen.

Awful truth: most of these 'must be 3 chip CCD camera, must be 422, must be better than 50 Mbits' are all 'riders on the contract' to prevent content producers 'cheaping out'. It's a semi-artificial barrier, a 'broadcast bouncer' to stop the hoi polloi from getting in. I love the BBC, I love Horizon, but even I am getting a little annoyed with the DSLR look done badly that has been creeping in under pressure from Producers.

But the nurse says I must rest now.

[Al Bergstein]

Thanks Ben and Matt for the overview. As Matt points out, Sad part is that there are numerous tv shooters on this and other forums doing news footage nightly with C100s.. And lots of local channels and cable are more than willing to take 4:2:o content it appears. So it's not a totally b&w issue. Likely a quality differentiator to lure advertsers to the big boys from the 'rest'. If broadcast networks look like youtube who's gonna advertise? And when i watch vimeo on my dsl tv it often looks like broadcast tv.

I love the look of my 4:2:2 xf305, but i can't cost justify a c300 at this time. Obviously in retrospect I would have bought it in the first place, but it wasn't out.

If we had a local tv channell where i live i would buy one, but it's an infrequent need. Like once in a blue moon.

[John Vigran]

Thanks for all the excellent posts here vis-a-vis 422 vs 420 on the C100.

I guess if I found myself with an extra $800 or so lying around, it might be put to better use on lighting or a nice lens......in the "real world", because I transcode almost everything I edit to ProRes anyway.....practically speaking, because I don't shoot in front of a green screen and my stuff rarely goes to broadcast, the whole 422 vs 420 issue is probably more of a psychological rather than a "real" one.

[Erik Naso]

Transcoding to ProRes from AVCHD doesn't give you anything extra other than a easier to edit file. In order to get 4:2:2 you have to record it with an external recorder. The extra color space is great for green screen and grading. I think most of the time the AVCHD codec holds up pretty well with the C100.

[Bram Corstjens]

A while back I had the opportunity to do a shoot where C100 AVCHD footage and Prores from the Atomos Ninja were recorded simultaneously.

There was only one instance where I spotted macro blocking. We were filming inside and this guy was standing in front of a window. The background behind him was very bright to almost white. And when he started moving there was a brief (1/2e second) moment of macro blocking around his hair against the white background.

Apart from this single problem I can tell you that I really could not tell the difference between the Prores 422 and the AVCHD. I did some pretty extensive side by side comparisons and the prores didn't look sharper, didn't give me better color correction, didn't provide better contrast/lattitude and didn't provide larger bit depth.

Ofcourse i'm sure it's possible to create artificial situations to 'break' the avchd codec, but under normal conditions it just really doesn't gain you anything spending dollars on a Prores Recorder

And with modern computers having GPU acceleration and fast CPU's the performance issues editing AVCHD are next to non existent. And I'd rather spend some money on a computer upgrade. An entry level Geforce will do the trick and you still have money left for a fast SSD and more memory. There would be more benefits compared to a 700 dollar Prores recorder

[Dave Partington]

Originally Posted by Bram Corstjens

…..apart from this single problem I can tell you that I really could not tell the difference between the Prores 422 and the AVCHD. I did some pretty extensive side by side comparisons and the prores didn't look sharper, didn't give me better color correction, didn't provide better contrast/lattitude and didn't provide larger bit depth.

I agree. I've also done lots of testing and in many instances the ProRes file was also noisier because it records the noise that the AVCHD filters out.

In some cases, yes I could tell the difference in 'sharpness', but it was always very tiny and always at the expense of more noise.

[Barry Goyette]

Here are a couple of 400% crops from some ungraded iso 2500 footage. Obviously you'd never look at the footage this way, this is just an example of what the differences are between the card and a file captured with the Samurai Blade in ProRes 422 HQ. Smearing of detail and increased "jpeg" type artifacts in the internal recording are the primary difference. When viewed in motion, flat areas in the mid shadows (say a dark grey studio background) will often vibrate and crawl, especially after grading...I found that the ProRes capture avoids this completely, displaying a preferable (to me) film-like noise.

[Matt Davis]

BTW, I've had the benefit of recording the International Association of Broadcast Manufacturers annual conference last week, and all this came up again. Which is why I repeat my mantra that the broadcast chain does horrible, horrible things to your work. I've been indoctrinated with '11 generations' and this easy little handle may have been devalued by some. Instead, we're talking about 'headroom' - a bit more ambiguous, but still relevant (interview with Andy Quested, Head of Technology BBC HD & UHD, BBC).

The ghastly truth remains: broadcast workflows really hammer the image AFTER you've delivered your perfect master. 4:2:2 is more robust. AVCHD's 4:2:0 is 'good enough' for most applications (97.5% of mine), but if I were doing my pet Magnum Opus project for the big screen, I'd want to do it 4:2:2. For that matter, someone filming a Sikh wedding (where it's reds rather than whites around the bride) would probably be better served by 4:2:2 too. LOL

[Pat Reddy]

Thanks Matt,

I shoot nature and landscape scenes with a lot of detail and generally like the whole scene to be in focus. Under these conditions I can see a noticeable but subtle difference between the AVCHD and Ninja 2 files. I got the Ninja specifically so that I could provide broadcast quality stock footage. But I still wonder if the AVCHD files from the C-100 hold up much better than, say, a DSLR clip once they hit the production chain.

It's hard to find a Discovery, Nat Geo, or BBC nature or outdoor reality production these days that doesn't make liberal use of GoPros. There are also a lot of shows shot on high-end cameras used in very difficult conditions. I am thinking in particular of a couple where the crew used Sony F700s but were not able to provide the necessary exposure control, focus, or stability to really take advantage of the camera. And then the style of editing these days is such that all that camera goodness can be washed away by the looks the editors and colorists apply to make the show "flashy". All this makes me wonder whether the Ninja 2 is really the way to go.