why device independent color?

In article ,
Martin Brown wrote:

On 27/01/2014 22:48, Eric Stevens wrote:
On Mon, 27 Jan 2014 10:29:50 -0800, isw wrote:


And just to keep things sort-of on topic, despite its limitations,
NTSC's color space was larger than that of any other commercial color
reproduction technique that existed at the time. (And that includes
color photographic film).

Wow!

That brings us back to Dale's original topic. You couldn't say "NTSC's
color space was larger than that of any other commercial color
reproduction technique that existed at the time" unless you had a
device independent space (such as "XYZ, CIELAB, CIELUV) through which
you can connect them.

Many thanks. :-)

Yes you could by showing that the other colour spaces gamut could be
represented as a subset of the NTSC colour space. I am not convinced the
claim is true about NTSC though it was for a while a de facto colour
space standard in practice.

You could just compare the area enclosed by the CIE coordinates of its
primaries to the others (which IIRC, was the origin of the claim ...)

I believe that claim came out at the time of the introduction of the
NTSC system. It would have been made with reference to the original red
phosphor, which was rather poor in light output and had a short lifetime
from being driven hard. The replacement red phosphor was much more
robust, but was located at different CIE coordinates (naturally). I do
not know whether the gamut claim was still true with it or not -- but I
think it was.

Isaac

isw wrote:
In article ,
Martin Brown wrote:

On 24/01/2014 23:47, Eric Stevens wrote:
On Fri, 24 Jan 2014 12:13:47 -0500, nospam
wrote:

In article , Dale
wrote:


what is needed is a colour managed workflow, with the image and each
device along the way having a profile.

that's how you get the profiles

no, you get the profiles by running the appropriate profiling software.

what the software does internally doesn't matter. users do not need to
understand all the math behind it to be able to use it.

what matters is does the user get what they expect, and the answer is
yes.

You are missing the point of Dale's original comment:

"you need to convert the device colors through device independent
color space like XYZ,CIELAB,CIELUV".

But that is clearly not true!

It is a lot more convenient to convert to a device independent colour
space and from there to whatever output medium you want to use because
the number of profiles need for N different image sources and M
destinations is limited to N+M colour profiles.

But you could with a *lot* more work compute direct colour profiles for
every possible combination of source and destination N*M. In the early
days when N was about 3 and M was about 4 that was what happened.

It may still make a lot more sense to store the original image in the
colour space where it was measured and only ever compute the device
independent form as a hidden step on the way to the output device.

What do you do years later, when all information about the creating
device's characteristics are long gone, and all you have is an image
file?

You know about embedded profiles, right?

BugBear