GH4 10bit 444 gh4 help

[Al MacLeod]

If that's all that has to be done then shooting in 1080 and converting to 720 should result in a 720 product with better color, or using an iphone at a 3k rate and resizing to 1080 for better color. I had never heard that benefit could be had.
Dang!

 

[DLD]

If that's all that has to be done then shooting in 1080 and converting to 720 should result in a 720 product with better color, or using an iphone at a 3k rate and resizing to 1080 for better color. I had never heard that benefit could be had.
Dang!

1080p is about twice the size of 720p. You need a 3-time difference to get from 4:2:0 to 444. 4K 4:2:0 is four times the size of 1080p, so there's plenty of "extra" pixels/color information there. Going from Full HD (1080p) to HD (720p) you get ~ 4:2:2 ... which is close enough for most intents and purposes.

A debayering process does it automatically anyway. A common DSLR resolution claimed as 1080p can fall anywhere between 650 and 850 lines after the debayering.

 

[Thomas Smet]

1080p is about twice the size of 720p. You need a 3-time difference to get from 4:2:0 to 444. 4K 4:2:0 is four times the size of 1080p, so there's plenty of "extra" pixels/color information there. Going from Full HD (1080p) to HD (720p) you get ~ 4:2:2 ... which is close enough for most intents and purposes.

A debayering process does it automatically anyway. A common DSLR resolution claimed as 1080p can fall anywhere between 650 and 850 lines after the debayering.

No you really need exactly 4x. 4k to 2k works because it is exactly half the horizontal and half the vertical resolution which is exactly the ratio 4:2:0 has with luma to chroma. In order for this to work when starting with 1920x1080 you have to down convert to 960x540 to get 4:4:4. If you start with 1280x720p you have to down convert to 640x360 to get 4:4:4. SD 720x480 would need to scale down to 360x240 to get the same 4:4:4 and so forth. Someday when we get 8k it can be scaled down to 4k to get 4:4:4.

 

[Thomas Smet]

If that's all that has to be done then shooting in 1080 and converting to 720 should result in a 720 product with better color, or using an iphone at a 3k rate and resizing to 1080 for better color. I had never heard that benefit could be had.
Dang!

This is true for any type of pixel image and not just video. The reason you don't typically hear about it is because video wasn't really thought of as ok to down convert to 1/4 the size and still be considered acceptable quality. 960x540 isn't really a real format so there is little reason for anybody to take 1920x1080 and down convert it to 960x540 just to get 4:4:4 unless you are delivering standard definition only. Since 4k is now rather excessive in terms of quality HD is still a very valid format to work with. In fact most big budget effects heavy Hollywood movies like Ender's Game, The Avengers, Guardians of the Galaxy and so forth are actually only edited, have effects added and mastered at 2k resolution due to cost. Whenever we go to a theater and watch a movie at best you are likely looking at a 2k movie. Elysium is one example of an exception where it was mastered at 4k and in some cases projected at 4k.

 

[DLD]

No you really need exactly 4x. 4k to 2k works because it is exactly half the horizontal and half the vertical resolution which is exactly the ratio 4:2:0 has with luma to chroma. In order for this to work when starting with 1920x1080 you have to down convert to 960x540 to get 4:4:4. If you start with 1280x720p you have to down convert to 640x360 to get 4:4:4. SD 720x480 would need to scale down to 360x240 to get the same 4:4:4 and so forth. Someday when we get 8k it can be scaled down to 4k to get 4:4:4.

A typical CMOS RGB sensor has one pixel for each color, which eliminates the need to debayer it. And 1080xRGB is 6.3 MPX.

In reality, 4:2:2 is pretty much as good as 4:4:4 under most circumstances, so a 4.2 MPX Bayer sensor (i.e., Alexa's 2880x1620) gives you a sufficient quantity of information. Likewise, F65 has what Sony terms as a Q67 (Q would stand for either quality or quantity ... or both, as the total pixel counts is 67% of RGB 4K) 20 MPX Bayer sensor, which is a 4:2:2 (8.8 + 4.4 + 4.4 = 17.6 MPX) in 4K. The same goes for Red Dragon (19 MPX) and Alexa65 (20 MPX), which are both 4:2:2 4K.

 

[zcream]

I am only interested in noise reduction. I have a movie I shot in 1080p and some scenes have stubborn noise I could not remove with Neat Video. How do I resize from 1080p to 720p in order to remove the noise ?

 

[TheDingo]

I have a movie I shot in 1080p and some scenes have stubborn noise I could not remove with Neat Video.

Just checking : You used a Neat Video camera profile made from "target" footage shot with exactly the same camera settings ? ( i.e. same ISO, same camera profile, same color temp, etc... )

 

[joe12south]

A typical CMOS RGB sensor has one pixel for each color, which eliminates the need to debayer it. And 1080xRGB is 6.3 MPX.

Unless I totally misunderstand what you're saying, no. Each CMOS photo site is monochromatic. it is only the filter put in front of it that determines its color. The most common pattern used to do so is the Bayer pattern, which emphasizes green in order to prioritize spacial resolution. But whatever the pattern. a full color image has to be reconstituted from limited color data.

You need a color filter, or 3 CMOS chips and prisms/mirrors. The only sensors I know of that sample full color at each site are the Foveons chips used in certain Sigma cameras.

 

[KINOKS]

Seeing as this thread has been brought back from the dead let me add my 2 cents regarding the 420, 422 and 444 debate.

A lot of you are arguing that there is little difference in 444 and 422 or even 420. And that 420 is enough. Well coming from a colorists stand point; compressed 420 is utter crap Plain and simple. Also 422 is better but please give me uncompressed 444 if at all possible. Where does it matter? It matters a lot, and by a lot I do mean A LOT in keying. And I am not talking about creating green screen keys but about normal keying that you do when grading. It's called "secondaries" and it entails creating keys of certain parts of the image. For example, you can key the skin tones in order to make a lift correction or to exclude them from the grade, etc. Or just separating the greens of the grass or the red tshirt that isn't the right hue or is to dark. Not a lot of serious color grading is done without this on a certain level. And having a high chroma resolution makes all the difference in the world when doing this (also compression matters a lot). Dealing with compressed 1080p 420 this can't be done really good. With this kind of footage you are basically confined in doing basic primary corrections and maybe simple secondaries with really highly blurred out keys (keys that don't have sharp edges but are really just a big blob).

So compressed chroma resolution does matter if you are grading beyond just simple primaries and simple push and pull grades.

Also I've been dealing with GH4 material in the last 2 years a lot. UHD to HD is great in terms of robustness. You can push the image a lot in the grade. But still you can't compare it to a proper uncompressed 444 footage. It still has lot's of macroblocking and weird hue discolourations blocks that make keying a lot harder and also limit you on how much you can push the footage.

Also this, Barry, shooting 422 UHD on an external recorder is going to greatly help on the above mention problems of macroblocking and hue. So I would still highly recommend shooting uncompressed UHD or at least Prores or DNxHR when planing on doing moderate grading. Sure, it wont matter that much in chroma (it will, just not THAT much) but in all other aspects it will be of great help

 

[joe12south]

Also I've been dealing with GH4 material in the last 2 years a lot. UHD to HD is great in terms of robustness. You can push the image a lot in the grade. But still you can't compare it to a proper uncompressed 444 footage. It still has lot's of macroblocking and weird hue discolourations blocks that make keying a lot harder and also limit you on how much you can push the footage.

Here, here. Macroblocking and color shifts are useful tricks for compressing a signal, but they do not survive the pushing and pulling of even a semi-aggressive grade. This is a big part of why internal V-LOG L is such a bag of hurt to work with in post...you HAVE to push a LOG image a lot to even get it natural looking, let alone stylized.

 

[Thomas Smet]

Seeing as this thread has been brought back from the dead let me add my 2 cents regarding the 420, 422 and 444 debate.

A lot of you are arguing that there is little difference in 444 and 422 or even 420. And that 420 is enough. Well coming from a colorists stand point; compressed 420 is utter crap Plain and simple. Also 422 is better but please give me uncompressed 444 if at all possible. Where does it matter? It matters a lot, and by a lot I do mean A LOT in keying. And I am not talking about creating green screen keys but about normal keying that you do when grading. It's called "secondaries" and it entails creating keys of certain parts of the image. For example, you can key the skin tones in order to make a lift correction or to exclude them from the grade, etc. Or just separating the greens of the grass or the red tshirt that isn't the right hue or is to dark. Not a lot of serious color grading is done without this on a certain level. And having a high chroma resolution makes all the difference in the world when doing this (also compression matters a lot). Dealing with compressed 1080p 420 this can't be done really good. With this kind of footage you are basically confined in doing basic primary corrections and maybe simple secondaries with really highly blurred out keys (keys that don't have sharp edges but are really just a big blob).

So compressed chroma resolution does matter if you are grading beyond just simple primaries and simple push and pull grades.

Also I've been dealing with GH4 material in the last 2 years a lot. UHD to HD is great in terms of robustness. You can push the image a lot in the grade. But still you can't compare it to a proper uncompressed 444 footage. It still has lot's of macroblocking and weird hue discolourations blocks that make keying a lot harder and also limit you on how much you can push the footage.

Also this, Barry, shooting 422 UHD on an external recorder is going to greatly help on the above mention problems of macroblocking and hue. So I would still highly recommend shooting uncompressed UHD or at least Prores or DNxHR when planing on doing moderate grading. Sure, it wont matter that much in chroma (it will, just not THAT much) but in all other aspects it will be of great help

100% agree except we do need to be careful to remember there are many quality damaging factors going on here and not just the chroma subsampling to blame here. If the GH4 had a 4:4:4 mode all of those horrible color and macro blocking issues would still be there. If there was such a thing as uncompressed 4:2:0 it wouldn't be nearly as damaging to grading as all the other stuff.

Without a doubt even with the GH5 and internally 10bit 4:2:2 I would still suggest using an external recorder. You can't cram that much visual data into a tiny H264 format without sacrificing something. I don't care about efficiency, I care about consistency.

 

[KINOKS]

100% agree except we do need to be careful to remember there are many quality damaging factors going on here and not just the chroma subsampling to blame here. If the GH4 had a 4:4:4 mode all of those horrible color and macro blocking issues would still be there. If there was such a thing as uncompressed 4:2:0 it wouldn't be nearly as damaging to grading as all the other stuff.

Yeah off course. Compression is actually just as bad or worse. So is noise. A low noise image needs less bandwidth than a high noise one. And in the case of GH4 the internal image processing unit isn't really the best. So everyone's best bet is just to avoid it - if they can

When doing HSL keys huge macroblocks ruin everything. But so does the lack of chroma resolution. And also specific to the case of GH4, in my experience, the blocks or small parts of the image that have a magenta push, really limit you in post.

 

[joe12south]

Yeah off course. Compression is actually just as bad or worse. So is noise. A low noise image needs less bandwidth than a high noise one. And in the case of GH4 the internal image processing unit isn't really the best. So everyone's best bet is just to avoid it - if they can

Basically, shoot compressed 4:2:0 and your colorist will punch you in the head. Shoot ProRes and it will only be a gentle thump. Shoot uncompressed RAW and they will kiss you.