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RE: RE>RE: Green light (again?!)

	Paul Grace wrote:

	In post production we strive for equal wide bandwidth  to allow
for precision keying in composites. This is why high end visual FX
houses use 4:4:4 in Ursa and Flame/Inferno .

	If you must do standard-def Flame/Inferno work on Ursa
originated material, then use 4:4:4 from the Ursa by all means. Better
yet, to remain in the high end classification of visual FX houses,
compare  your blue-screen results with Spirit 4:4:4 from the same film.
If the phrase NO-BRAINER is unspoken during the comparison, then I owe
you one cellar temperature Timothy Taylor's Ale.

	There seems to be a Spirit color resolution misconception in
spite of Mikael Reichel's detailed explanation. In standard-def video
there are only 720 active pixels per line with 360 chroma samples to
define the color bandwidth for 4:2:2. That doubles to 720 chroma samples
for 4:4:4, hence the better SGI compositing edges. 

	For simplicity, consider a severely crippled Spirit WITHOUT its
hi-res luminance CCD array. All you have now is 960 each R,G,B samples
per line when sized for full ap in 35mm. If you size for academy 35mm
horizontally then you make use of about 88% of each CCD array which is
about 845 elements of each color sensor.(higher bandwidth than needed)
This gets decimated in a digital filter to 720 samples when in 4:4:4
mode. Its like having a ClearView but in the horizontal direction. It
should be quite apparent that the Equal Wide Bandwidth that you strive
for is present on both the Ursa AND Spirit. Don't confuse the HD
resolution arguments with those involving 4:4:4 NTSC or PAL!

	Disclaimer: I don't get much free stuff from Philips, Cintel, or

	BTW: Our Spirit doesn't break, but then our Ursa Diamonds don't
break either. Neither company understands telecine engineer job
security. :)

	Randy Reck
	Encore Santa Monica

Thanks to Peter Stansfield for supporting the TIG in 1998..
No product marketing allowed on the main TIG.  Contact rob at alegria.com
945 subscribers in 36 countries on Tue Mar 24 13:55:22 PST 1998 
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