Is RAW 4:4:4?

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Insomniac

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Is RAW 4:4:4?

PostTue Nov 12, 2013 9:17 pm

Is RAW 4:4:4, or is the BMPCC still recording in 4:2:2 color space in RAW mode? Thanks!
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Remo Pini

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Re: Is RAW 4:4:4?

PostTue Nov 12, 2013 9:20 pm

I don't think 4:2:2 or 4:4:4 apply to RAW as the debayering is done in Resolve (or whatever else you use to do it). For the sake of simplicity, I'd say RAW is 4:4:4 equivalent.

Or am I making a fool of myself?
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Mac Jaeger

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Re: Is RAW 4:4:4?

PostTue Nov 12, 2013 9:35 pm

I'd say: regarding the density of color information this bayer pattern raw is more like 4:2:2 than 4:4:4; however it's not the same, so you should convert only to 4:4:4 formats if you want to keep as much color information as possible.
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Tom

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Re: Is RAW 4:4:4?

PostTue Nov 12, 2013 11:04 pm

remopini wrote:I don't think 4:2:2 or 4:4:4 apply to RAW as the debayering is done in Resolve (or whatever else you use to do it). For the sake of simplicity, I'd say RAW is 4:4:4 equivalent.

Or am I making a fool of myself?



You are correct, 4:4:4, 4:2:2 etc describe chroma sub sampling. Such terms are not applicable nor comparable to raw data, even if its from raw bayer data.
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Frank Glencairn

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Re: Is RAW 4:4:4?

PostTue Nov 12, 2013 11:15 pm

Actually...

(Nerd mode on)

raw data isn't even color - it's just black and white (greyscales).

The color comes to existence in the computer, with the dabayering process.

(Nerd mode off)
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Corrupt Frame, Inc.

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Re: Is RAW 4:4:4?

PostTue Nov 12, 2013 11:46 pm

Frank Glencairn wrote:Actually...

(Nerd mode on)

raw data isn't even color - it's just black and white (greyscales).

The color comes to existence in the computer, with the dabayering process.

(Nerd mode off)


You have an on/off switch for your NERD? Damn having one of those would have helped me out a lot in high school...
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Insomniac

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Re: Is RAW 4:4:4?

PostWed Nov 13, 2013 12:25 am

Thanks for the clarification.

I understand that 4:4:4 color space is better for keying/green screen work than 4:2:2. I was excited for the BMPCC to get the RAW update because I mistakenly thought it would mean the camera would record 4:4:4.

Do you have any idea how RAW recording should impact keying/green screen work as compared to the camera's ProRes mode, if at all, and how it likely compares to 4:4:4 footage for the same, which I understand to be the "holy grail" for such work? Thank you for your time!
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Sean Pfeiffer

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Re: Is RAW 4:4:4?

PostWed Nov 13, 2013 1:20 am

Insomniac wrote:Thanks for the clarification.

I understand that 4:4:4 color space is better for keying/green screen work than 4:2:2. I was excited for the BMPCC to get the RAW update because I mistakenly thought it would mean the camera would record 4:4:4.

Do you have any idea how RAW recording should impact keying/green screen work as compared to the camera's ProRes mode, if at all, and how it likely compares to 4:4:4 footage for the same, which I understand to be the "holy grail" for such work? Thank you for your time!



My exact understanding of the nuts and bolts of keying isn't what it should be, but as far as I gather, most chroma and other forms of keying rely on the software being able to tell the difference between the color values in two separate pixels. Now, this is gathered by reading the values in each channel which is usually RGBA. So, I think that whatever debayering or sampling is done is irrelevant, the only thing that matters is the per-channel color information contained within each pixel.

I know for a fact that both Nuke and Flame typically work with frame sequences rather than video clips. So I don't even think that things like color and chroma sampling like 4:2:2 and 4:4:4 even apply. I'm not sure about AE though.
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Remo Pini

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Re: Is RAW 4:4:4?

PostWed Nov 13, 2013 9:36 am

(half baked knowledge incoming...)

S_Pfeiffer wrote:So I don't even think that things like color and chroma sampling like 4:2:2 and 4:4:4 even apply. I'm not sure about AE though.


If you debayer something from RAW to RGB (not YCrCb which I don't think any of the common programs is doing), then you have "equal" amounts of color information present in the channels (AFAIK 12 bits in the case of BMD RAW).

However, due to the design of the sensor, you usually have only HALF the resolution in R and B as opposed to G (which is one of the reasons that using a GREEN screen makes the most sense).

I'd say that keying off of a debayered RAW DNG frame sequence should generally be simpler and more accurate than off of a 4:2:2 ProRes stream.

BTW, I don't think stream vs. sequence has any bearing on 4:4:4 vs. 4:2:2 (see http://en.wikipedia.org/wiki/Chroma_subsampling).

Side note: It would be interesting to know the actual pixel/photosite counts for each color of the BM(P)CC sensor.
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