ProPhoto RGB, why gamma 1.8?, was: Monitor to monitors displaying the same image
ProPhoto RGB, why gamma 1.8?, was: Monitor to monitors displaying the same image
- Subject: ProPhoto RGB, why gamma 1.8?, was: Monitor to monitors displaying the same image
- From: Chris Murphy <email@hidden>
- Date: Sat, 21 Jul 2007 13:20:32 -0400
On Jul 16, 2007, at 2:22 PM, Andrew Rodney wrote:
Anyone know the rational why Kodak used the same working space gamma?
ROMM (ProPhoto) has an 8bpc and 16bpc implementation, and with the
limited precision offered with 8bpc with such a huge space, going
from XYZ to RGB back to XYZ could produce significant errors in
blacks. The steeper the TRC (tone response curve), the bigger the
reversal error. So a TRC defined with gamma 1.8 was chose, largely
for reversibility. It's a useful characteristic because, of course,
we convert captures into that space for editing and then we convert
them out of the space for output.
This is why I think it was a mistake for ECI to move to an L* based
TRC with ECI-RGB 2.0, as it still is advocated for use with 8bpc
workflows. ECI-RGB 1.0's TRC is gamma 1.8 based, and thus I prefer it
over Adobe RGB (1998), which has a similar TRC, defined as gamma 2.2.
Chris Murphy
Color Remedies (TM)
New York, NY
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Co-author "Real World Color Management, 2nd Ed"
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