Re: saturation rendering
Re: saturation rendering
- Subject: Re: saturation rendering
- From: Graeme Gill <email@hidden>
- Date: Sat, 16 Sep 2006 11:43:04 +1000
eugene appert wrote:
The following two sentences, both from definitions of saturation rendering
> intent have lead to discordant understandings among my
colleagues. The first is "Saturation just tries to
> produce vivid colours" from Fraser, Murphy Bunting, and
> the second, "Saturation requests a highly saturated rendering"
> from Adobe Help. Both of these phrases seem to be saying that
> source colours will be more saturated in the
target space. Among us there are those who believe that
> saturation rendering realigns and compresses the entire
> space to maintant visual relationships based on saturation much
> like perceptual does with tint, and others who believe this
> rendering intent increases colour saturation.
Can anyone straighten us out?
The answer is that the saturation intent rendering of a particular
profile depends on the profile making software and the options
chosen at the time it was made. The ICC specification does
not pin down a precise algorithm, so it is up to the ideas
and inventiveness of the authors of the profiling software.
From the ICC V4.2 spec:
"0.3 Rendering intents
The colour rendering of the perceptual and saturation rendering intents
is vendor specific. The former, which is useful for general reproduction
of pictorial images, typically includes tone scale adjustments to map the
dynamic range of one medium to that of another, and gamut warping to deal
with gamut mismatches. The latter, which is useful for images which contain
objects such as charts or diagrams, usually involves compromises such as
trading off preservation of hue in order to preserve the vividness of pure
colours."
and
"6.2.5 Saturation intent
The exact gamut mapping of the saturation intent is vendor specific and involves
compromises such as trading off preservation of hue in order to preserve the
vividness of pure colours."
While some profile makers create saturation intents transformations that
are only good for charts (because they distort the color space too
severely or abruptly to be usable with images), others provide
gamut expansion (expanding the source gamut in areas where the
destination gamut is larger) and even saturation enhancement
while maintaining a smooth mapping, resulting in a saturation
intent that is perfectly usable for pictorial images as well as
charts.
Graeme Gill.
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