Panasonic GH4 in a professional setting - FAQ

[svendson]

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...

 

 

I brought this up in another thread, but made the mistake of comparing the decision to Cannikon feature crippling, and my technical questions got lost in fanboy defense, unfortunately.

 

I've since found some interesting discussions on the Black Magic forums, where they talk about this same issue but with regards to 60p, instead of 422 10 bit. The basic issue seems to be the amount of data you are feeding _into_ the encoder, not the data rates coming out of it.

 

Some more looking around, and the issue seems to be with affordable encoder technology lagging the rest of the camera subsystems a little. As noted in this thread, the Odyssey 7 seems to be the only reasonably affordable device that can capture 1080p60, but it does it at 8 bit 422. Blackmagic and a bunch of other recorders do 10 bit 422, but only up to 1080p30. I guess there are must be some high end recorders that can do 10 bit 422 1080p60, but I suspect they must be running some pretty low production volume encoder chips (expensive) or using FPGAs for the encoding (even more expensive).

As such, given the current choice in the low budget segment seems to be high frame rate 420 8 bit, or max 30 fps 422 10 bit, I think Panasonic made the right call for differentiating their product. Certainly, as a rank amateur looking for a hybrid camera to take snowboarding and kiteboarding, the high fps appeals a lot more than 10 bit 422.

[smoke23]

Does anybody know if the screen info still disappears after 10 seconds with the new OLED screen?

[see ya]

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).

 

Yes, however my comment was more about the suggestion that just scaling down 4K 4:2:0 gives 4:4:4 and the kind of suggestion then it's the same as 4:4:4 which could have been encoded directly in camera, rather than quality loss in general.

 

So adding 4:2:0 to a timeline in an NLE or grading app that works RGB for scaling, color work and effects will probably first convert the 4:2:0 to RGB by interpolating chroma based on the full 4K resolution, not scale luma and keep chroma resolution, if anyone want's 4:4:4 in 1080p from the 4K RGB, whats the point? interpolation to RGB has lost the YCC relationship and chance to scale luma down keeping chroma at it's original resolution?

 

Alternatively as I understand it, in Premiere for example  4:2:0 is kept as long as it's cuts only, so after editing and no colour work, 4:2:0 YCC could be rendered out at 4K intact for another app to do the scaling. Or does Premiere offer scaling luma and maintaining chroma resolution from the original 4:2:0?

 

Premiere immediately upsamples 4:2:0 internally to 4:4:4 by interpolation for color work and effects so again if there is no chance to scale luma and not chroma difference channels it's a typical 4:2:0 to 4:4:4 interpolation even at 32bit rather than scaling luma and maintaining chroma?

 

So just wondering where exactly the simple 4:2:0 4k equals 1080p 4:4:4 statement holds true other than theoretically?

 

Chroma in YCC is the difference of a RGB value once the luma has been extracted for the brightness of the RGB sample, and scaling luma down will involve interpolation / averaging of the luma values in the downscale, what's to say the corresponding 4:4:4 or RGB values generated after the downscale are equivilent to any original 4:4:4 data that might have been sample in camera, circling back to the suggestion that 4:2:0 to 4:4:4 by scaling is somehow the same as 4:4:4 in camera?

[Xhain]

The PIX 240 doesn't do 1080p50... 

With this brick underneath (so SDI out) I suppose 1080p50 / p60 will work with some recorders - with the 7Q I’d expect also in 10 bit, perhaps even 444 12 bit? Suppose this is still to be awaited, Convergent Design may have to adapt firmware etc. - so I doubt anybody can predict this now…  

Recording with the brick is probably safer anyway, because micro-HDMI being fiddly and the location of the slot on the cam. 

So I suppose that’s interesting for a lot of users - personally I’m not sure about the brick: don’t find any info reg. weight yet, but it looks like a killer for run+gun / low-budget, with the external power supply needed etc.. 

So perhaps I'd "have to live with" 4k + 444 1080p25 ... *sigh* LOL

[andy lee]

nice in depth GH4 review here -

 

http://www.imaging-resource.com/PRODS/panasonic-gh4/panasonic-gh4A.HTM

[theSUBVERSIVE]

Shame about the lack of a robot arm. Panasonic should have learned by now it's an essential tool to scrape all the RAW meat off the dishes.

 

More importantly though is if it flies, I'm always ready to spend a few more bucks it something can take flight.

[jcs]

@yellow- while YUV (et al) <=> RGB is technically lossy ( http://en.wikipedia.org/wiki/YUV ), it's not nearly as lossy as the DCT, quantization, and motion interpolation (when interframe compressed). I would be surprised if one could see any significant difference after converting to/from YUV and RGB. My guess is they compute: 420 to 444 YUV, then transform YUV to RGB, then downsample to 1080 from 4K. Quality will be excellent.

[Scoutpro]

Andrew, excellent info as usual;appreciate all your efforts. This may be a bit elementary, but a big concern for me. Has Panasonic fixed the issue with the display, in particular, the audio meters from vanishing while recording?? I have no need for the "Brick" and would like to rely on the on-board meters, etc. Great news regarding the focus peaking remaining active while recording! Thank you.

[Tony Anastasi]

none of the reviewers hands on has answered two very simple but important questions i feel i would want to know -1. whats the internal battery run time when shooting video - 2. whats the actual recording time limit, 29.59 minutes or non-stop until the battery or card runs out ? - thank you 

[tosvus]

the second item has been answered by multiple reviews I have seen. For "ntsc", there is no recording limit. If you switch to pal/25/50, 30 min limit due to EU restrictions.

none of the reviewers hands on has answered two very simple but important questions i feel i would want to know -1. whats the internal battery run time when shooting video - 2. whats the actual recording time limit, 29.59 minutes or non-stop until the battery or card runs out ? - thank you 

[Tony Anastasi]

the second item has been answered by multiple reviews I have seen. For "ntsc", there is no recording limit. If you switch to pal/25/50, 30 min limit due to EU restrictions.

 

what a pita.. i'm working on a doco in China ( pal ) and from Australia ( pal also ) - my multicam interviews rarely go over 20-25mins however i do get the odd corporate event that i'm obliged to shoot also.. so that means running about hitting start/stop of different cams, start one five mins after the first so that gives me five mins to walk over to the other cams etc.. pita i tells ya!.. vity needs a hack out asap haha :)  - and yes you can say go grab a camcorder but wheres the fun in that ?! 

[aldolega]

If you switch to pal/25/50, 30 min limit due to EU restrictions.

 

 

Not from what I've read- the 30-minute limit just has to do with where you buy the camera. If you buy an EU model it will have the 30-min limit, all others will not. All the cams from anywhere can switch between NTSC to PAL.

 

So EU people who need unlimited record will have to import a cam from the US or somewhere else.

[see ya]

@yellow- while YUV (et al) <=> RGB is technically lossy ( http://en.wikipedia.org/wiki/YUV ), it's not nearly as lossy as the DCT, quantization, and motion interpolation (when interframe compressed). I would be surprised if one could see any significant difference after converting to/from YUV and RGB. My guess is they compute: 420 to 444 YUV, then transform YUV to RGB, then downsample to 1080 from 4K. Quality will be excellent.

I'm not disputing that scaled down 4K to 1080p will look better, I'm just querying how 4:2:0 4k can make 4:4:4 1080p because of the acertion chroma is quarter resolution ie: 1080p that's all. Where do you see that seperate scaling taking place? Without going to RGB first from full 4k?

[tosvus]

Ok, maybe some clarification needed. I read that Panasonic this time only makes one model, not two like in the past.

Not from what I've read- the 30-minute limit just has to do with where you buy the camera. If you buy an EU model it will have the 30-min limit, all others will not. All the cams from anywhere can switch between NTSC to PAL.

 

So EU people who need unlimited record will have to import a cam from the US or somewhere else.

[nib187]

16. Does it have a robot arm that extends into the kitchen to do the dishes?

 

No.

 

You made my day!

[ntblowz]

Or just use your phone to remote control the camera, if the distance is not too long. Currently Panasonic is the only one that allow full control over wifi (include manual focus).

 

what a pita.. i'm working on a doco in China ( pal ) and from Australia ( pal also ) - my multicam interviews rarely go over 20-25mins however i do get the odd corporate event that i'm obliged to shoot also.. so that means running about hitting start/stop of different cams, start one five mins after the first so that gives me five mins to walk over to the other cams etc.. pita i tells ya!.. vity needs a hack out asap haha :)  - and yes you can say go grab a camcorder but wheres the fun in that ?! 

[AaronChicago]

If you go here: http://www.phototools.com/product/LUMIX-DMC-GH4-Body-Black/DMCGH4KBODY/143526.html

 

Click on "Select Accessories"

 

They have the DMC-YAGH listed at $2199.00!

[Andrew Reid]

The price hasn't been set yet. These sites are having a guesstimate to generate some early orders.

 

I've seen the GH4 body price vary by as much as $500!

[leeys]

Nice FAQ, thanks!

That makes sense since the Extreme cards are only rate to 45Mb/s. You may want to correct your article as only the PRO cards are rated to 95Mb/s and you say that the 95Mb/s cards won't work. Also, the UHS-I PRO card doesn't do 280Mb/s, that is reserved for the UHS-II cards.

I'm now getting a little confused. Sandisk rates their cards in MB/s, while bit rates are measured in Mb/s. There's a factor of 8 between the two, right? So we're talking about 750 Mb/s for the Extreme Pro cards, and 500 Mb/s for the new Extreme cards (80 MB/s read, 60 MB/s write), or did I miss something in my thinking?

[Homerus]

I was wondering. I'm considering buying either a 5D mark III for RAW or a GH4. Both have their ups a downs, but both of them (as far as I've been able to see) produce stunning images. Sensor size is kind of a biggie for me though.

 

I've put the ups and downs for me here:

 

I own Contax Zeiss lenses, which are 35mm. Full frame ftw. (+1 for 5D)

I already own a Sandisk 64gb extreme pro card, which I can use with the GH4. (+1 for GH4)

GH4 is much cheaper (+1 for GH4)

Recording modes (+1 GH4)

Rolling shutter (I'm guessing +1 GH4)

Noise (I'm guessing 5D still beats the GH4 here?)

External Add on with XLR and SDI (+1 GH4)

Magic Lantern (+1 5D)

 

Here are my concerns really, can anyone tell me how the 5D's RAW holds up against 4K H264? As far as I can see, both look great... on the internet that is.

 

Cheers