[Tig] ProRes444 necessary when grading BW

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Sun Mar 17 17:14:53 GMT 2013

On Sun, 17 Mar 2013, David HJ. Lindberg wrote:

> What the clients wants is bw which I guess it's true bw, true gray. Although are there any benefits with saving just
> a few percent of the colors in the picture, even if it's not that noticeable? 
> "21.26% red, 71.52% green, 7.22% blue."
> This got me thinking, when adding bw effects where you can adjust parameters like the red, green and blue channel
> does that mean we're adjusting the percent of how much of the different channels is affecting the bw effect?

This would mean that you are actually editing the image as RGB and 
just viewing (or converting it back) in/to gray.  Converting to gray 
is a one way trip.  If you want to edit using RGB controls then you 
probably want to edit in RGB or else harm will surely result.  The RGB 
image can always be converted to gray using simple math but if the 
intent is to output gray, you would want to continually monitor the 
gray equivalent.

Decide if you want to edit in pure gray (and disable any color-type 
controls) or if you want to edit in RGB, monitor in gray, and then 
(irreversably) output as gray.

Someone else mentioned that ProRes444 supports 12-bit samples.  If it 
is possible to edit the image as RGB in 10-bit "422" (a YCbCr thingy) 
while monitoring in gray, and then output to a gray format with more 
depth, then you could still have more gray levels than 10-bit (given 
suitable quality math) but there would be a small loss in 
horizontal resolution.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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