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Andrew Reid

Discovery: 4K 8bit 4:2:0 on the Panasonic GH4 converts to 1080p 10bit 4:4:4

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Panasonic GH4 4K

Pros are wondering what the benefit of 4K is to them in terms of overall image quality, when mastered and delivered for 2K / 1080p. A lot of work is still shot in 1080p and cameras like the Canon C300 are the workhorses of the moment.

In the case of the GH4 it may appear from the specs that it's just an 8bit 4:2:0 camera internally.

Actually the theory is 8bit 4:2:0 4K material from this camera can be taken through a workflow in post that converts it to 10bit 4:4:4 1080p - with all the smoother tonality, better colour and workflow advantages that format brings. This is a big leap for 1080p based on the much more expensive C300 which only does 8bit 4:2:2.

I asked Go Pro's David Newman (Sr. Dir. Software) whether this theory was correct...

Read the full article here

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Andrew

 

I love this cutting edge stuff. Hope you can continue to supply us with genuinely interesting news rather than the advertorial content of some sites (you know who I mean).

10bit 4:2:2 is more useful to me than 4K at the moment so this news is……….very welcome.

 

Keep up the good work.

 

Rich

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So I finally got the answer! I asked this twice without much success but I didn't know it would get so technical and the result is quite above what I thought it was possible.

 

In the end, 4K to 1080p in post is the way to go for better results.

 

My question was:

 

In theory, what should be the differences for the GH4 in terms of IQ between:

 

1) GH4's 1080p (@100mbps IPB or @200mbps All-I)

2) 1080p via external recorder ProRes 10-bit 4:2:2

3) 1080p resized from GH4's 4K footage (post)

4) 1080p crop from GH4's 4K footage (post)

 

I don't know if the differences will gonna be big but 1080p (10-bit 4:4:4) from 4K footage should be the best, followed by ProRes 10-bit 4:2:2 and I think that as both are 8-bit 4:2:0 and I think Panasonic's codec should be good, the differences between the crop and the direct from the camera output should depend on the subject, conditions and what do you want to do with it. The 4K cropped will have heavier compression but I don't know if the differences are going to be that noticiable.

 

Actually, unless you make the whole testing in different scenarios and light situations, we can only speculate if the differences in terms of final results are considerable enough to each person and workflow. Depending on your use, it may not be worth going through all of that. But the big news is that you won't need an external recorder to extract the maximum of a 1080p footage, you just need to shoot in 4K and have more time and a better computer - than you would if you were going to work on just 1080p.

 

This simply makes the GH4 even more awesome in terms of cost-benefit and flexibility.

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About the YAGH:

 

Only the DMW-YAGH add-on base can output 4K (uncompressed, 10bit 4:2:2) from the GH4

 

Is there some gain by using this 10-bit 4:2:2 to generate the 1080p 10-bit 4:4:4 instead of the internal codec from the camera (4K 8-bit 4:2:0)? Or is the difference just marginal?

 

It's getting very video-nerdy but it would be interesting to see all the tests for all these scenarios.

 

- 1080p (10-bit 4:4:4) from 4K (10-bit 4:2:2 via YAGH HDMI)

- 1080p (10-bit 4:4:4) from 4K (8-bit 4:2:0 Internal codec)

- 1080p (10-bit 4:2:2 microHDMI)

- 1080p (8-bit 4:2:0 Internal codec All-I @200mbps or IPB @100bps)

 

It may look like too much but I think it's interesting to know the degree of difference between these options, so people can choose the best workflow for their need.

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It is a naive idea, but nevertheless...

 

If 4K/8bit/4:2:0 from the GH4 card converts to 1080p/10bit/4:4:4, can 4K/10bit/4:2:2 (grabbed by YAGH) be converted to something like 1080p/12bit/4:4:4 etc. ?

 

PS I suppose a good idea would be to contact Panasonic directly to answer if  all these manipulations are feasible. 

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This is great news indeed!

Nice work, Andrew!

This camera is shaping up to be a game changer, for sure.

 

Now cue the complainers bitching: "I don't have time to transcode my footage to prores/cineform! My computer will explode! This camera sux! BMPC 4K is better! Alexa is even better! Herp derp!".

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Well, I'm just glad I left Canon and Nikon for Panasonic. Bought the cheap G6 for now, but this GH4 lurking around the corner is beautiful, especially with this type of info! Just curious about the workflow though, do you have to process each individual clip through AE before getting 10bit 4:4:4?

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Using error diffusion dithering, it is mathematically true that a 8bit image oversampled by a factor of 2 (4K) can contain the same information as when downscaled to the intended resolution (2K/1080) as a 10bit image originated at 2k/1080.
 
 
But, the codec must do just that, employ error diffusion dithering and do it correcty.
 
Somebody needs to dig up a whitpaper on the codec.
 
Summa summarum, if handled correctly at the encoding stage using error diffusion/dithering, increased spatial resolution can absolutely compensate for lack of bit-depth.
 
It's the fundamental principle behind most (if not all) printing techniques - substitute the word "encoding" above for "rasterizing" and you are in the print world. If you want to, you could describe offset printing a 1-bit process - there is ink, or there is not ink. That's why photos that go to print need much higher resolution than what you would watch on a screen.
 
Joachim

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Perhaps rather BMPCC (1000$) would be the first one ?

 

The BM pocket aint consumer level.  It's nearly impossible to use for anything pro, let alone for consumer use...  The average consumer doesnt spend £300-£400 on media to get an hours worth of recording time, a decent evf, rigging, and lenses to fulfil consumer purposes.  The gh4 will deliver everything a consumer needs while also servicing the enthusiast, professional and semi pro sectors.  

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The BM pocket aint consumer level.  It's nearly impossible to use for anything pro, let alone for consumer use...  The average consumer doesnt spend £300-£400 on media to get an hours worth of recording time, a decent evf, rigging, and lenses to fulfil consumer purposes.  The gh4 will deliver everything a consumer needs while also servicing the enthusiast, professional and semi pro sectors.  

 

I just pointed "Messerjocke" that GH4 (1500€) is not the first camera "cinema quality camera" below 2K.   

 

Cinema quality is a very broad term, and since GH2 and 5D shot films have been shown in cinemas, let's not even go there ;)

 

Sure, I would say a "reliable cinema quality"  is somewhat above 4:2:0 and 8 bit/color at 1080p :).  

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Shit..... if only panasonic could have put 5axis IBIS inside !!!!!!! 

Each time I read a news about a new product, we get something super nice. But it is always in a different body ! 

Will we ever get a whole package which does GH4 quality (with good codec and bitrate + 24p 60p) + IBIS + good stills quality ? 

Next hope I have : future Sony FF dslr .... which should have IBIS and hopefully a better thing than their awful AVCHD...

 

Why is it too much asking this in 2014 ? The camera manufacturers don't want to make money or what ? I don't understand. Really. 

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Shit..... if only panasonic could have put 5axis IBIS inside !!!!!!! 

 

 

There is a (very reasonable) opinion around that the cameras operating with such high bit rates at the moment cannot provide IBIS, since they need a solid connection to the heat sink. However, I do agree that the still-oriented cameras from Panasonic (GM1, GH3, GX7 ...) must incorporate 24p/25p/30p at least, mic/head jacks  and of course a competitive IBIS (except perhaps GM, for which it probably would not make much sense due to the size limitation).

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