[argyllcms] Re: Perceptual intent

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 19 Dec 2014 08:12:20 +1100

robert@xxxxxxxxxxxxxxxxxx wrote:
> Correction: here is the correct link to the image in my previous post:
> 
> http://www.irelandupclose.com/customer/argyll/perctest.jpg
> 
> The top image is a relative mapping to the destination while the bottom
> image is a perceptual mapping to the destination.  Notice how much lighter
> the grays are.

Hi,

I don't know the details of what I'm seeing here (what colorspace
is this in - it doesn't seem to be tagged, so is it sRGB ?), so
it's hard to be sure, but on my display, nothing terribly odd is
going on in the shadows, if this is an absolute preview. The blacks
are raised about 2-3 dE - exactly what one would expect given that
the printer black is L* 3. There's no way of avoiding that without
clipping shadows.

The mid-shadows are perhaps brighter than I would expect -
but it's hard to look into it any further, without the source
image. Do you have a link for that ?

> and
> there are also some much more saturated colours (look at the orange patches
> for example)

My guess is that these are in the original, and that the slight shift in
luminance range together with the greater tradeoff flexibility in the perceptual
mapping, has made more gamut available.
But I can only confirm this by looking at and working with the original image.

Graeme Gill.


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