fcp vs ae&shake (yuv vs rgb)

[Paul Coull]

Hi,

What have you used to capture the footage in the first place?

grafxflow

grafx that flow!

[Adam Taylor]

Shake works in a wide range of colour formats – you can use the colorspace node to change to and from rgb, cmy,hls,yiq,yuv .

its well explained in the manual, and also the tutorial books by Marco Paolini.

not so sure how its done in AE though.

adam

Editor/Mixer
Character Options Ltd
Oldham, UK

[Rafael Amador]

Hi Martin,
The main issue is that in RGB you can get color combinations that are only ‘theoretical”. i.e When you open the color-picker window in Photoshop with some color values some times you get a yellow triangel that means that this color mix (RGB) it can not be displayed. (The same happens when working with CMYK. When you get a yellow triangle that means that you can not get that color by mixing the four colors for printing).
The YUV color space is just a part RGB space. All the colors that you can get in YUV falls inside the RGB spectrum. But many colors from the RGB falls out of the YUV spectrum. So when you pass from RGB to YUV (or YCbCr) there are many colors that are mapped to the closet color avalaible.
Another issue is the “Broadcast safe “. In the digital domain you can manage values of bright and color that are not supported (?) when you pass to analog. So you must keep your signal between certain levels to avoid problems when broadcasting.
How to resolve those issues? I think there are only two things to do:
– Keep Broadcast safe in AE by using a VideoScope (for exaple Testgear).
– Export from AE with a YCbCr codec.
Cheers,
rafael

[Graeme Nattress]

Actually, the YCbCr colour space is much larger than RGB, so you can make totally illegal colours in YCbCr that cannot be displayed in RGB. I think you’ve got your explanation in reverse…..

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Russell Lasson]

So FCP is YUV and AE 7 is RGB from the way I understand it.

So when you go from FCP to AE 7, select the footage and choose interpret footage. At the bottom of the box there is an option that says “Expand ITU-R 601 Luma Levels.” Select that. It should compensate correctly.

I never really figured out how to do it in AE 6.5 but it had something to do with the levels filter.

-Russ

[Rafael Amador]

I’m very sorry. I always thougth that the YUV color space was more reduced than the RGB. As the most part of the people that have been editing analog for years I haven’t face the RGB world untill recently. And I face it with a real lack of information and knowledge.
I tend to assimilate YUV with YCbCr and I know they are not the same thing at all, but I don’t know the real difference (appart of the digital fact). There is any book or document where I can learn about that? I promisse I will study it and try don’t missinform nobody else (starting by my self) 🙂
Cheers,
rafael

[Graeme Nattress]

Poynton is probably the best place to start. It can be heavy, but it has all the info you need. His book HD TV and interfaces, details at http://www.poynton.com

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Rafael Amador]

Thanks Graeme. I’l try to get the book.
By the way I want to ask you something. In one post of you about Betacam SP, you wrote: Do that mean that a DV NTSC 420 would have very little vertical resolution and wouldn’t give enough quality? Would them be PAL 411 too good for a no-Professional standard? Is it worth to pay the difference of price for the PAL DVCPro comparing with MiniDV or DVCam?
Thanks,
Rafael

[Graeme Nattress]

The way that PAL gets transmitted, they phase alternate each line so as to correct for any chroma imbalance in the transmission – that’s why you don’t need a “hue” control on a PAL set, but you do on NTSC. This will sacrifce some chroma vertaical resolution, but overall, as you have more rez to begin with, and view accurate colour, you get a much better picture.

PAL DV is hence 4:2:0 as the horizontal chroma rez is more important.

However, 4:2:0 is a pain to work with properly for interlaced TV, hence NTSC uses 4:1:1 which is much easier.

So, 4:1:1 is a better compromise for NTSC and 4:2:0 is a better one for PAL. PAL DVCPro is 4:1:1, as it’s much easier on the interlace processing.

Graeme

– http://www.nattress.com – Film Effects and Standards Conversion for FCP

[Rafael Amador]

Thanks again Graeme.
Cheers.
Rafael