Re: Media Testing for maclife.de
Re: Media Testing for maclife.de
- Subject: Re: Media Testing for maclife.de
- From: Graeme Gill <email@hidden>
- Date: Mon, 15 Sep 2008 11:33:40 +1000
MARK SEGAL wrote:
Uli, There are two colour spaces involved with Lightroom - (1) the working space of the
application itself, which is kind of ProPhoto but with gamma of 1.0 (rather than 1.8)
in order to match the native 1.0 gamma of raw camera files; this is hardwired; and (2)
the choice of working space gamuts for the output image exported from Lightroom - which
is where you have the choice of three gamuts as I mentioned before. The only default is
Actually, the color spaces chosen aren't (technically) that important in themselves.
What's important is the range of channel values that are carried in the colorspace
by the application, and any rendering or clipping performed when encoding into that
colorspace.
This is because an additive tri-stimulus colorspace can use any (non-degenerate)
three primaries as their basis, as long as there are no limits on the
channel values. Color values outside the triangle formed by the primaries
can be addressed by a combination of negative or > 1.0 values. Similarly
gamma encoding is irrelevant, because it can be removed when needed.
A limitation of most traditional raster format encoding is that they
can only carry values that are between 0.0 and 1.0 (encoded as a fixed
point binary, say 8 or 16 bits etc.), and so typically the gamut will
be limited to the primaries triangle, and so a gamut clipping or
gamut mapping (rendering) is forced at this point. Of course
if the raster file is intended for display on output devices
(such as displays or printers), then an output rendering is
often in fact desirable :-)
Graeme Gill.
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