your thoughts on color grading gh4 footage?

i like my sony fs100 but at 28mps and 420/8 bit, one of its weak spots is pushing the avhcd footage in post.

as i continue to explore a possible gh4 transition, i need to ask:

since the gh4 footage is also 420/8 bit, what has been your experience color grading gh4 footage?

how far can the gh4 footage be pushed before it starts to "break-up" due to noise and/or micro blocking?

any thoughts, links or footage is appreciated.

be well.

rob
smalltalk productions/nyc

The problem with pushing AVCHD footage is often more about the NLE / Color software & user than it is with the source footage.

People talk about things breaking up all the time, then you find they're trying to push things a couple of stops and even ProRes can look bad in those situations.

I've not had any problems grading GH4 footage in FCPX. Noise is there in 4K at higher ISO levels, but it's reasonably grain like rather than Canon chroma noise. Neat video deals with it easily and if you're downscaling to 1080p then it's even less of a problem.

Just FYI I tend to shoot in .MOV rather than AVCHD on the GH4. I have no real idea if that makes a difference.

I recall reading somewhere If you are going to finish in HD you can shoot 4k and transcode to ProRes 4:4:4:4 10 bit.
That should be nice and robust for grading!
Sorry for the vagueness; I don't have time at present to find the discussion. Someone way smarter than me said it was theoretically possible, whether anyone has actually tried it yet I don't know.

Maybe on the Cow? I'll try to find it when I get a moment.

Cheers,

The only thing I know is if I edit 8bit footage in a 10bit project in edius I get less banding in the sky so a 10 bit edit environment does have a effect but I honestly don't believe you can turn 8bit 4:2:0 into 10bit 4:4:4, I guess it's the same if I convert avchd to a hqx avi codec, it is much easier on the system to colorcorrect in that way but you can't get something out which wasn't there from the start.

But I have to say that 4k footage from my gh4 does allow quite some correction before it starts to fall apart, only don't expect miracles.

Found it. There is even an app to do the conversion.

Discovery: 4K 8bit 4:2:0 on the Panasonic GH4 converts to 1080p 10bit 4:4:4 - EOSHD (http://www.eoshd.com/2014/02/discovery-4k-8bit-420-panasonic-gh4-converts-1080p-10bit-444/)

Cheers,

Oh, there you found that info, then it has to be true ;)

Actually David Newman is the developer of Cineform so at least he knows a lot of what he speaks. Not sure why it has to be ProRes 444? I wonder if there's a noticeable difference if you used ProRes LT?

Yes, but anyways, if it comes 8bit 4:2:0 out of the camera, it cant magically become 10bit 4:4:4 after that? I could convert to 10 bit 4:2:2 hqx as well but that doesn't mean the conversion alone adds all the missing colour information, unless that is hidden in the 8bit 4:2:0 codec?

Think about the upcoming Shogun, that will allow to record UHD with 10bit 4:2:2.

This will be a real improvement especially for color grading of GH4 footage.

Sorry if I wasn't clear. It becomes apparent when you read the article. 4K when DOWNCONVERTED to FHD can be resampled at 4:4:4:4 in 10 bit.

Because there is a lot more information in the 4k image it can mathematically produce 4:4:4:4 @ 1920x1080 by some clever interpolation. I don't pretend to understand it but when I read David Newman said it was possible I though it was credible.


Cheers,

The high data rate saves it and it holds up a lot better in general compared to 1080 formats on other cams. My workflow involves 4K -> DPX sequences for compositing and there's been no shots where I couldn't get it to look how I wanted it as long as it was exposed well. This little thing is impressive.

Sorry if I wasn't clear. It becomes apparent when you read the article. 4K when DOWNCONVERTED to FHD can be resampled at 4:4:4:4 in 10 bit.

Because there is a lot more information in the 4k image it can mathematically produce 4:4:4:4 @ 1920x1080 by some clever interpolation. I don't pretend to understand it but when I read David Newman said it was possible I though it was credible.


Cheers,

I cannot imagine that this is right really. Especially this point:

"Yes to CineForm 2K/1080 4:4:4. Luma precision can be increased to 10bit. Four 8-bit values some (sum) to one 10-bit value."

Theoretically that sounds right - in reallity you have 256 luma and 256 color values with 8bit - and 4x256 = 1024 luma and 1024 color values with 10bit.

BUT the point is that you can have 256 different colors in 4 pixel only. When you mix up 256 different colors, why do we think that we can end up with 1024 different colors corresponding to the original colors? At the best it is a color mixture that is an approximation of that reallity!

I mean, if you wish to end up with 1024 colors you have to shoot with a color and luma precision of 1024 = 4:4:4.

In addition, in the long run we may want to have 10bit with 4K too. So I think here we will love the Shogun since it delivers true 10bit with true 4:4:2 also for UHD/4K. That is an important difference.

The vast majority of the Keith Gavin footage in this video was shot in 1080p60@100Mbps, Cine-D flat as hell to match with a C100 in C-log for the other footage. Crushed and pumped by the editors, seems to have gotten along OK.

FPL 2: Ruth vs Gavin IV - Flowrestling (http://www.flowrestling.org/coverage/251881-FLO-Premier-League-2/video/753870-FPL-2-Ruth-vs-Gavin-IV#.VIEDgoue95g)

About converting 8bit 4k footage to 10 bit HD footage. If you have four pixels in 4k and you convert to HD - the four pixels will be converted to one - right. If the four pixels have the same colour it will give that colour! But if one pixel have a different colour you will get a new mixed colour in 10bit! A colour you did not have in your 8 bit footage but a colour that will represent a colour closer to what your eye original saw!
Thats my thoughts!!

People who have tried it have found that this process yields zero gain in color correction. Anything from EOSHD is automatically to be discounted.