Re: When black is white (or blue is black) was: CMYK spaces used for document creation
Re: When black is white (or blue is black) was: CMYK spaces used for document creation
- Subject: Re: When black is white (or blue is black) was: CMYK spaces used for document creation
- From: Karl Koch <email@hidden>
- Date: Wed, 4 Nov 2009 16:49:30 +0100
Martin,
now we are getting somewhere and this thread becomes interesting again.
You show the amount of ignorance that is common with the common user!
You try to convert from one to the other RGB working space – and both
are matrix based. In a matrix based profile there is only one way of
converting (not quite true, but good enough if we talk Adobe
Photoshop): relaive colorimetric.
You can´t expect to convert out-of-gamut colors this way, so that they
would show detail after conversion.
When building an ICC-DeviceLink profile, you can specify different
renderings, e.g. image based in the case of Argyll. This seems to be
the case in your idiot example. If I do a "normal" perceptual
compression, this is the result:
http://files.me.com/basicc/aec8yi
Yes, it is easy – if you know what you are doing!
So, you can see that there are several ways to color heaven. And, as
Albert Einstein found out: Everything is relative ;-)
This doesnt´say that Photoshop is flawless, but you´ll have to find
other instances ;-)
Best regards,
Karl Koch
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free profiles for standard printing conditions:
http://colormanagement.org
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Am 04.11.2009 um 15:54 schrieb Martin Orpen:
About the RAW issue -- aren't you going to explain why you used the
term RAW repeatedly when you wrote Adobe's technical paper (and an
embarrassing number of other items) but criticise other people when
they follow your example?
On 4 Nov 2009, at 14:06, Andrew Rodney wrote:
It is for most of us!
Who's "us" -- people like me who actually have to convert images
professionally? Or people like you who talk about converting images
professionally?
The point of my original post -- the bit that you snipped -- was
that this "conversion" is problematic and that you can achieve
much more impressive results by doing this outside of Photoshop.
Using ICC profiles was in your first (and several other posts).
Then you decide later you’ll define the conversion with a device
link, then you decide you’ll not also try the device link in
Photoshop.
Enough of the theory, let's take a look at a practical example.
Here's an image in ProPhoto RGB. It's a tough one because even my
wide gamut display is struggling to show the detail in those
saturated colours:
<http://inside.rgb2cmyk.com/images/urni_test.tif>
I need a web version so I'll take your advice and convert it in
Photoshop:
<http://inside.rgb2cmyk.com/images/urni_test_PS_sRGB.tif>
That's disappointing because the detail that was there has now gone
completely! I thought you said that this was easy? Did you forget to
tell me that RGB to RGB conversions in Photoshop mean that all out
of gamut stuff just gets clipped away?
I know, let's use a device link to see if we can get a bit more of
that image into sRGB:
<http://inside.rgb2cmyk.com/images/urni_test_DL_sRGB.tif>
Wow! I'm getting all the detail now... and that ProPhoto blue
primary is so beautifully bl... bl... dark green...
--
Martin Orpen
Idea Digital Imaging Ltd
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