June 29, 2014

Downscaling Panasonic GH4 Footage from 4K to 1080P with Dave Dugdale

Dave Dugdale of Learning DSLR Video recently produced a terrific review of the new Panasonic GH4, which shoots 4K internally to SD cards. Since the majority of work is still being finished in 1080p, he's been downscaling most of the stuff he's shot to 1080p, but he wanted to explore the differences between downscaling in the timeline or after he's finished editing in a 4K timeline in Premiere. He also addresses people accusing him of being paid off by Panasonic for his review.

While you may not see any real differences if you're not doing much to the footage, the other advantage to working in a 1080p timeline with 4K footage is that you're able to crop or stabilize the frame however you need to and still end up with a high-quality 1080p result. At the moment this is one of the huge benefits to 4K, that you can do a lot to the image and retain detail for a beautiful 1080p finish. Even if you're not going to be showing your work in 4K, having that extra resolution to play around with can be extremely helpful.

Check out more over at Learning DSLR Video.

Link: GH4 Tutorial Downscaling 4k Footage to 1080 -- Learning DSLR Video

Your Comment

35 Comments

The main reasons (crop and stabilize) for shooting 4K now. If your directing a film it's a no brainer. Nice work Dave and Joe.

June 29, 2014 at 4:04PM, Edited September 4, 11:56AM

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Joanathan

Hey guys, I am wondering if anyone out there can answer my question. I have tried out 4k footage on a 1080 time line..but..when I add stabilization... premiere says it cant do it because it doesn't match the timeline... is there a way to fix that?? THANKS

June 29, 2014 at 4:10PM, Edited September 4, 11:56AM

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Miguel

Nesting the clip first should solve your problem.

June 29, 2014 at 4:14PM, Edited September 4, 11:56AM

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Caleb

Hey Caleb, do you mean drag them to the timeline, the nest and add the stabalization?... Would I keep them aall nested after that?

June 29, 2014 at 4:25PM, Edited September 4, 11:56AM

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Miguel

Make a timeline in your project called "Stabilizing Camera A001" then drag whatever clip you want to stabilize into that. It'll ask if you want to change your sequence settings to match, click "Change to Match". Apple Warp Stabilize to your clip, let it do it's thing. When finished and happy with your result, right click and select Nest. That will make that clip nested. Then take that clip into your main edit timeline.

June 29, 2014 at 5:12PM, Edited September 4, 11:56AM

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Phil McTaggins

THANKS SO MUCH GUYS!!!!!!

June 29, 2014 at 8:07PM, Edited September 4, 11:56AM

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Miguel

Miguel if your using Premiere just right click on a clip and select NEST and it will take that clip and set it up in a new timeline for you and then just stabilise it. Easy that way.

July 1, 2014 at 7:25PM, Edited September 4, 11:56AM

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One question here: when you nest your 4K clip in your 1080p timeline, does it still retain its 4K details? If not then you loose the advantage of the 4K...

October 28, 2014 at 9:13PM

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JF Noel
13

The description under this video may help in your case, don't know,

"Firecoresoft converted the 4K footage to ProRes 422 (HQ)1080p before importing into NLE on a 1080p timeline". http://vimeo.com/97596843

June 29, 2014 at 5:11PM, Edited September 4, 11:56AM

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Enjoying Some G...

No. There is no need to do this... At all.

June 30, 2014 at 3:03PM, Edited September 4, 11:56AM

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Tom

George Carlin was right...there are a lot of brain-dead morons in the world! Sadly, a lot more than he imagined.

Panasonic makes a great, innovative 4K video DSLR...many reviewers including Dave Dugdale come to that same conclusion. Suddenly there are accusations of bribery and collusion between Manufacturer and Reviewer!. I remember that Philip Bloom also faced similar unwarranted slander a couple years back.

Where do these conspiracy theory dead-shits come from? Not everyone has to agree about the merits of a given camera...but why make false and outrageous accusations about a competent reviewer?

June 29, 2014 at 8:46PM, Edited September 4, 11:56AM

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Skeptikal

You know what would really be interesting , it would be interesting if Nofilmschool.com actually posted an original review or original content to give its audience a perspective not coming from info of others. I cant remeber the last time this site reviewed anything.

I remembered coming to this site to great tips and info and now its just a repost site with occasional bad editing on info.

No hate just seems lazy for a site not to have one single section or area of reviews and also its time for this website to upgrade comments or layouts, you can not even reply properly to because the outdated comment box does not position replies in order.

Again this is not hate, if you reread the facts you will see that i'm stating facts. How about you guys do a proper review and do more than a basic repost.

Trolls coming in 3,2,1

June 30, 2014 at 2:52AM, Edited September 4, 11:56AM

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cJay

Hey

June 30, 2014 at 9:38AM, Edited September 4, 11:56AM

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Troll

*slow clap*

June 30, 2014 at 10:15AM, Edited September 4, 11:56AM

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Noah

Pretty much all the other sites do is reviews. Thank you NFS for providing content other than reviews.

Once you go down that road, forever will it control your destiny......

July 1, 2014 at 7:31PM, Edited September 4, 11:56AM

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@simon stop trolling and being a suck up , there are several sites in fact all other film sites offer reviews aswell as repost content ,

Any regular Joe could purchase a word press template and repost material , all I said is that it would be great if this site actually did a review from time to time and gave an original content perspective other than others .

Its funny that one can't make legitimate opinion without being considered hate or trolling , sad sad

July 1, 2014 at 9:50PM, Edited September 4, 11:56AM

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cjay

Philip Bloom does have a GH4 video fresh out this morning. Yes, it is a great camera. No bribery needed to see that.

new Philip Bloom GH4 video: http://vimeo.com/99523009

June 30, 2014 at 10:21AM, Edited September 4, 11:56AM

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Enjoying Some G...

OK...lets all now go and make some "comments" on Troll and Mater Dead-Shit charles Benincasa YouTube page and let him know how the internet really works...

http://www.youtube.com/user/cazz77

June 29, 2014 at 8:58PM, Edited September 4, 11:56AM

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Skeptikal

Another great reason to downscale 4:2:0 4K to 1080p is as long as you are operating within a 16/32bit project you are essentially now working with 4:4:4 10bit 1080p material :)

June 30, 2014 at 7:52AM, Edited September 4, 11:56AM

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Not entirely sure if you have to export it in a 10bit wrapper first or if it works straight off the timeline though so that's food for thought.

June 30, 2014 at 7:56AM, Edited September 4, 11:56AM

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Uhmmm... I'll be rough: NO. 420 is 420. No matter what you transcode to the quantization remains the same. I do wonder where your pretty crazy idea came from?

June 30, 2014 at 2:08PM, Edited September 4, 11:56AM

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John, I think Kraig is talking about chroma subsampling as opposed to quantization, i.e. sampling (recording/registering) chroma channels less frequently than luminance, thereby allowing luminance to remain sharp while letting colour blur slightly to save space/bandwidth (4:2:2 means that for every 4 luma, there are 2 chroma samples). It stands to reason that if you have 4:2:0 4K footage (1/2 the vertical chroma rez of 4:4:4, _and_ half the horizontal chroma rez), and you downscale it in half vertically and horizontally in a 4:4:4 project, your resulting image is now 4:4:4 in 1080... you're not creating new chroma samples, but rather you're removing (interpolating) half of the luma samples in the downrezzing process.

Of course, I've not tried this... and as with any up/downrezzing operation, its quality is liable to depend on the interpolation algorithm used and the nature of the original footage.

June 30, 2014 at 3:21PM, Edited September 4, 11:56AM

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Lee Henderson

I also wondered if downscaling 4.2.0 4k would give effectively 4.2.2 because like you say, there are twice as many pixels. Is this how it works? I need clarification before I swap my canon! :(

June 30, 2014 at 3:48PM, Edited September 4, 11:56AM

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Alex

Ehmmm... no.

4:2:0 is 4:2:0 whichever way you look at it. You're mistaking resolution with compression. Once you compress, mostly if you go all the way down to 8 bits, there is no way you can extrapolate the colour values you have discarded previously. Say you've a 10 bit 444 source, for example, this means that any of the three RGB components have a set of 1024 possible values. If you go down to 8 bit you end up with 256 possible values.

In other words, instead of 1024 possible levels of saturation on your reds, you have 256.

However, when you're talking 8bit 4:2:0 you are not even talking RGB any more, but a highly compresssed iteration, depending on manufaturer, of YCrCb material. Green is no longer a component, but the result of an algebraic operation between the other two. This is because green is like the opposite of our earthling skintones, so it's the one component we can mistreat without apparently messing up the image too much for pure and simple viewing. Just think for a second what you are doing to those 256 values I mentioned before. They are not getting any larger.

SO: There is no way you can extrapolate all those missing tones in any component after discarding them. Downrez it and, as the article almost says, you'll improve sharpness (Y is luma and is les compressed), but the colour is gone, and it's gone forever and evermore, Lenore.

(I actually work as DIT)

June 30, 2014 at 4:36PM, Edited September 4, 11:56AM

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When working with 4:2:0 files you have three channels (red, green and blue) in different resolutions (with green being the same as the best your camera can resolve, 4K in this case), and by going to an image 4 times smaller than the original your "evenning" (is that a word? to even something, right?) all three channels, in a way.
So by downrezzing 4K footage to 1080p you're essentially getting 4:4:4 but that's the problem in the original statement: that's all you get, because 8bit stays 8bit, that's color information you won't get back.
Chroma sub-sampling improvement is another thing, and it's one that works in this case unlike color depth.

June 30, 2014 at 6:14PM, Edited September 4, 11:56AM

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Sorry to reply to myself, but I want to keep the conversation contained to where I think it belongs to.

I've been asking colleagues over here, mostly after finding a certain article in the Eoshd website that kinda almost got there, but left it too soon.

The right answer is somewhere between what I was saying and what you guys are saying.

If we merge two high resolution 8 bit pixels to form a new lower resolution one, and the values of these two pixels are 123 and 124, for example, the resulting pixel's value is 123.5. In order to represent this result we must then go to 9 bits, as we need to enlarge our set of numbers in order to be able to represent the improved granularity.

In the case at hand, QHD to HD, four high res pixels merged into one, we must then add another bit as, for example, we might need to be able to represent an increase of .25 instead of .5.

Now, what needs to be brought into this is the scientific concept of "measurement accuracy". These new colour values are algebraic, statistical facts; hence they are not necessarily the same thing as the real deal. So, yes, you'll end up with 10 bits, but the precision of these new values is exponentially lower, by a factor of four, to the precision that'd be achieved with, say, an Alexa shooting natively at 1080p 4444.

What it means is that, yes, you will improve colour depth, but the precision of these new values is exponentially lower to doing it natively.

My guts tell me this is not an ideal solution when you think of the importance and subtle variations of skintones. But yes, it beats the much lower precision of 4k 4:2:0 and it'll definitely improve aliasing if done within the right maths, 32 bit float strikes me as the best of all possible paths for this.

July 1, 2014 at 6:25AM, Edited September 4, 11:56AM

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Cheers for the extra info dudes. Great debate on this but I'd like to try this out properly and confirm this with some real world footage. I'll try and find some GH4 footage later and try pushing it at 4K and then converted to 1080p in 32bit float :)

July 1, 2014 at 6:43AM, Edited September 4, 11:56AM

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Ps. I think I understand what you are saying though - that the image captured was only 8bit to begin with so the data was missing to begin with, therefore there is no getting it back. I wonder how this is actually perceived though as surely that is all that matters right?

July 1, 2014 at 6:47AM, Edited September 4, 11:56AM

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No worries matey!

By all means do test it, I'd definitely suggest Davinci Resolve or Scratch for this. Also try going aces, maybe even using EXR instead of Prores or similar. There's not much else around with the same quality.

However, if you want an informed corollary, here it goes:

The increase in colour depth is the result of mathematical need, the need for more numbers to represent the new values. However, these new values are STATISTICAL FACT, not the same as fact. In a best case scenario, they're at best 1/4 as precise as native. But you must then bring other physical phenomena, such as noise, that decrease even further the achieved precision.

Given the, say, ineffability of the aesthetic perception of a skintone, I would bet all the money I don't have on these skintones lacking the appeal you'd get going native. I've worked with Alexa since it came out, and my eyes converted long ago to the religion of the F55's skintones. 16 bits are always better than 10. So I'm be pretty sure 10 bit native is better than 10 bit through maths.

July 1, 2014 at 6:57AM, Edited September 4, 11:56AM

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Yeah I hear ya dude! Almost everything I'm handed nowadays is Alexa, RED or F55/F5 and it's hard to explain but there is something almost tangible you get when grading either raw or true native 10bit (even the BMCC) footage which you simply don't get with 8bit (which I'm sure you know what I mean)? It just FEELS more solid if that makes any sense? I'm actually looking for a little something that fits in my bag as I'm missing the fun in just shooting for the sake of it and having a little run and gun for personal stuff so it was gonna be the BMPCC for me because I genuinely love grading the footage out of the 2.5K but if this little cheeky number gets close to this "tangibility" I'm rattling on about then I may actually go and grab one of these :) Ps. Love your work dude! Kraig.

July 1, 2014 at 10:17AM, Edited September 4, 11:56AM

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Oh maaaan, thanks for the kind words. It's very appreciated, mostly after checking out yours which is pretty sleek indeed.

I'd say, if you ain't going to shoot for a client, don't bother about any of what I've said. It's only when ambition is at stake that I think one should get the best that's available, if only to the number of wtfs further to a minimum. And yes, I do wonder why on earth I haven't yet got the BMCC?

Actually, yes, I remember, Blackmagic is not AJA.

July 1, 2014 at 10:40AM, Edited September 4, 11:56AM

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I'm back, quit too soon and I'm off this week (or most of it).

Kraig, you wrote this: " It just FEELS more solid if that makes any sense".

It makes a lot of sense, and it's quite interesting that you're using "solid". An online editor friend of mine likes to call it "brittle" when working on lower quality material. You can do a very quick test by putting a sample of each codec (you can simply take a clip and make a new version transcoded to a lower bit depth, say 4444 and 422 proxy to make the differences more obvious) on top of each other on the timeline. Bring a garbage matte to the clip on top and split it down the middle, top to bottom. Then open up the waveform and observe how very different the waveforms are. One side will have steps, the oher will be more continuous. Then go on and shiver about what this is doing to the skintones. It's a sin.

Just don't do it on the old FCP as it's 8 bits processing all the way and it'll look the same (...shit...).

Peace.

July 1, 2014 at 11:00AM, Edited September 4, 11:56AM

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Gud work Dave :)

July 3, 2014 at 8:34PM, Edited September 4, 11:56AM

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Wesley Brown

This was an all-around awesome thread. Thanks all!!!

July 22, 2014 at 6:35PM, Edited September 4, 11:56AM

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Jonathan

Hi Dave. Just writing to let you know I've got a gh4 based mostly on your recommendations Im still in the early testing phase but so far so good. Your review was the main reason for purchasing the camera, although i watched Philip Bloom and Tom Antos reviews also. I just wanted to thank you for your reviews and the work you put in helping the rest of us trying to figure out all this brain melting stuff. You sir are a legend! Maurice

November 20, 2014 at 2:38PM

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