[argyllcms] Re: Checking profile with GrangerRainbow

  • From: posts@xxxxxxxxxxxxxxxxxxxxxxxxx
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 04 Oct 2016 17:20:59 +0200

Hello Ben and Graeme,

thank you very much for your clarifications.

I think I understand what you mean. However, I had thought, that the differences between no profile applied and one of the -ax,-as,-al versions applied, are more subtle. Especially I was astonished about the sharp edges and the magnitude of the differences.

But as you say, this could all be due to the algorithms and extrapolations. I was just curious to see, if I made a serious mistake. If I apply the -ax and the -al profiles to a real image, I still see, of course, differences, but they are not as dramatic as in the synthetic Granger Rainbow.

Best wishes


PS: I had sent this mail before but with an attachment demonstrating the difference between -ax and -al. But obviously this freelist does not accept attachments, since also previous mails with attachments to the Argyll-list disappeared without any error message.

Zitat von Ben Goren <ben@xxxxxxxxxxxxxxxx>:

On Oct 3, 2016, at 4:38 PM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:

an input device typically is a different observer, and
so doesn't "see" color the same way as a standard observer.

For those who might (as I once did) have trouble warping your brain 'round that...consider a printed yellow and a visual match on a computer display, and maybe even another matching yellow from an LED bulb. All look the same but have radically different spectra. Your camera might actually be able to see them as different colors.

Or, consider humans with various color deficiencies. You might see the numbers in the chart of dots, but your nephew might not. There will be other charts that you can't see the numbers but your camera will, and vice-versa.

The math all works out, but the underlying idea is that all these devices (including your eyes) are basically spectroscopes, but with really low spectral resolutions such that, rather than, say, a few dozen bands of a few nanometers each (like in an i1), you've got three bands of dozens of nanometers each -- and the spectral characteristics of the three bands aren't the same.

...of course, our eyes (and cameras) have far more spatial resolution than any spectroscope, even while their spectral resolution is extremely limited....



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