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Andrew Reid

Panasonic GH4 in a professional setting - FAQ

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Perhaps I'm just  not reading very closely, but is 96fps on available as slowmo in 24/30 as converted by the camera? Or does it actually record 96 and allow you to edit as you wish in post?

I believe it is recorded at 96 in 1080 and then puts it in the wrapper of your choice. If it didnt do this then when you put it onto a timeline it would try and be a 96 fps timeline, so you would need to interpret footage every time. Anyway, if you record it into the 25p wrapper but then came edit time and you wanted it in something else I guess you could just use "interpret footage" and bobs your uncle. All the frames remain there, it just changes how quickly it plays them back.

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I hope it's not bothersome as I already asked it before but here we go again, hopefully I'll get a reply this time.

 

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)

 

If there is, which should have the best sharpness, DR, less artifacts, less moiré, etc?

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This sounds DAMN good to me so far! It sounds like down-rezzing 4K material will give me material suitable for green screening, which is a big plus in my book. It will be interesting to see how the footage in 4K vs 1080p holds up in terms of compression artifacts though. Unless I read this wrong, the 1080p footage should theoretically have more headroom in their codec(s).

 

I'm also waiting anxiously to hear about if gh4+any recorder can output/receive 96fps realtime, in case I buy a recorder down the line.

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How about the Hyperdeck Shuttle 2 as external recorder?

 

Yea... much cheaper than the Atomos, albeit without a built-in monitor, but a good option for those who are happy to use the camera's screen, or already have a monitor they're happy with. I just wish the Hyperdeck could do >30fps for 10-bit 4:2:2. Perhaps a new (but still affordable) model will be unveiled at NAB, or if we're lucky, a firmware update.

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Scaling down to 1080 in Premiere will be very high quality (Lanczos+bicubic) and will easily run in real-time with CUDA/OpenCL: http://blogs.adobe.com/premierepro/2010/10/scaling-in-premiere-pro-cs5.html (Max Quality is always on for scaling with GPU accel).

 

420 QuadHD and higher will indeed scale down to 444 1080p (with additional vertical averaging acting as a low pass filter to help reduce aliasing). Depending on the compression quality, shooting in 420 QuadHD can produce higher quality vs. 1080p. If for example AVCHD 1080p ultimately does a better job due to bitrate relative to frame size, it might look better in some scenes (> HD resolutions appear to be limited by card write speeds).

 

If those resizers work in RGB then a lot of the benefit of scaling 4:2:0 YCC source is lost? The mix has been done and the chroma subsampling scaled down accordingly in the conversion to RGB.

 

If a YCC resizer is used and the resizers allows the ability to scale luma and chroma channels seperately including the ability to offset chroma or luma to suit chroma placement in the source. ie: whether it's left of centre or centred, then interpolate to 4:4:4, then convert to RGB typically in the NLE or grading software for grading a 'better' result should be seen.

 

Resizing is preferable as one of the last opps before encoding to delivery, using Lanczos resizer at input, then grading / sharpening etc can lead to ringing and halos. It's really just oversampling edges, is it not?

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4:2:0 in 4k simply means that the luma resolution is 4k and the chroma resolution is full hd, so it actually will give you 4:4:4 in 1080p. which brings up the question why it cant just record 1080p 4:4:4 natively. or at least 4:2:2...

 

if premiere really features lanczos (i cant confirm) it could be sharper than any other 1080p picture. pretty cool!

 

is he simply wrong about the IBIS? that would be a game changer even if its just 3-axis.

 

that would leave me with just my 2,3x crop complaint, which is probably gonna stay. shit panasonic you could have gone with a multiaspect and given us 4k with a 1,86 crop. instead youre going in the opposite direction...

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If those resizers work in RGB then a lot of the benefit of scaling 4:2:0 YCC source is lost? The mix has been done and the chroma subsampling scaled down accordingly in the conversion to RGB.

 

If a YCC resizer is used and the resizers allows the ability to scale luma and chroma channels seperately including the ability to offset chroma or luma to suit chroma placement in the source. ie: whether it's left of centre or centred, then interpolate to 4:4:4, then convert to RGB typically in the NLE or grading software for grading a 'better' result should be seen.

 

Resizing is preferable as one of the last opps before encoding to delivery, using Lanczos resizer at input, then grading / sharpening etc can lead to ringing and halos. It's really just oversampling edges, is it not?

 

Many of the effects work in RGB- I would expect everything to be converted to RGB after loading (and don't see any reason why there would be any noticeable quality loss when everything is computed in 32-bit float).

 

Ringing and halos come from the negative lobes of the filter (see link which describes how the filter works), however Lanczos 2 is supposed to provide the best balance of quality vs. ringing/halos. The goal is to downsample (in this case) while preserving as much detail as possible while preventing aliasing. The real-time versions perform a Gaussian blur before downsampling with bilinear (result will be a softer image). All pixels are processed the same (edges don't get special treatment).

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The idea that Panasonic has hamstrung the in-camera recording to 4:2:0 instead of 4:2:2 because it is incompatible with some set top boxes is the stupidest thing I have ever heard.  Perhaps a deal-breaker.  The whole idea of 4/3 format is to deliver the greatest possible quality with a smaller footprint and now we must rig up with external recorders so someone can watch birthday parties from the reader on their BluRay player?  Amazing.

 

For God's sake, someone with a connection to Panasonic prevail upon them to make it switchable to 4:2:2.  Please!

 

 

 

 

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I believe it is recorded at 96 in 1080 and then puts it in the wrapper of your choice. If it didnt do this then when you put it onto a timeline it would try and be a 96 fps timeline, so you would need to interpret footage every time. Anyway, if you record it into the 25p wrapper but then came edit time and you wanted it in something else I guess you could just use "interpret footage" and bobs your uncle. All the frames remain there, it just changes how quickly it plays them back.


At first I assumed that it must be something to do with limited frame rates in the AVCHD standard but I don't think that the FS100 does this. It must be some limitation of the camera otherwise I can't imagine why you would want it conformed to a particular frame rate in camera rather than doing it in post.

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At first I assumed that it must be something to do with limited frame rates in the AVCHD standard but I don't think that the FS100 does this. It must be some limitation of the camera otherwise I can't imagine why you would want it conformed to a particular frame rate in camera rather than doing it in post.

 

I can think of a reason. Play back in slow motion on the camera LCD. Pertty cool huh?

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I hope it's not bothersome as I already asked it before but here we go again, hopefully I'll get a reply this time.

 

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)

 

If there is, which should have the best sharpness, DR, less artifacts, less moiré, etc?

 

1. Can't say for sure but this will probably be fairly similar to what the gh3 already does, perhaps a little better

2. Much more latitude for grading due to the 10 bit  (4 times as many levels to work with), twice as much chroma resolution for smoother colour gradients and less aliasing round edges of high colour difference like red against white.

3 (assuming from in camera 8 bit 4k) same grading latitude as internal 1080p.  Will definitely look sharper displayed at 4k vs up-scaled 1080. Will definitely look sharper if you have to re-frame or zoom in compared to 1080 zoomed in. Will most probably look sharper when downscaled to 1080 than 1080 due to the oversampling, even if the bit rate is lower.    No all I-frame in internal 4k so complex movements may be rendered worse in the compression process than all I-frame 1080p.

4. will have the least detail of all as you'd be cropping out 75% of the 100bps information.  Would probably be acceptable in certain shots but you wouldn't want to make a habit of it.  Better to use a longer lens or use the in camera 1080 crop.

 

All in all I think the right setting would depend on what you wanted from that particular shot.  If you wanted more spacial resolution you would chose 4k. if you wanted a wider field of view, the narrowest field of view, slow motion options or more temporal resolution you would go for 1080.

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Hi,

 

Good questions : is it possible to capture prores 4:2:2 with hyperdeck shuttle 2 ? It cost only 400$, it will be great option.

 

Thanks !!!

 

I suppose you can, why not - but the Shuttle doesn't do 1080p50 / 1080p60, so that'd be a disadvantage... Didn't check on the other recorders so far (no time right now, sry) - maybe someone else can have a look? Since it's indeed relevant.... Otherwise I'll check later - I mean downconverting 4K to 444 1080p would really be great - and all the same, you won't get 50p / 60p that way either. Clean 1080p50 at 10bit 422 would be my preference in most cases...

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