CHROMiX

Are all CMM's created equal..?

Recently, I have had cause to wonder about the inner-workings of the CMM as it relates to RIP’s.

Of course, I have a basic round-about awareness of what the CMM is - but I’m wondering about the specific functions the CMM is responsible for performing.

Would someone(s) please run a list for me, or give me a link to a related technical paper or reference?

Thanks!

Here’s one link: boscarol.com/pages/cms_eng/073-cmm.html

I’m sure there are other sources of info…perhaps the ICC’s website. I have seen differing results between CMM’s (Colorblind compared to …well, everything else), but for the most part, you likely won’t see significant differences from one CMM to the next…and one of the goals of the ICC v4 spec was to clear up this possiblity.

At 10:13 AM -0700 9/17/05, christ0pher wrote:

Recently, I have had cause to wonder about the inner-workings of the CMM as it relates to RIP’s.

Of course, I have a basic round-about awareness of what the CMM is - but I’m wondering about the specific functions the CMM is responsible for performing.

Would someone(s) please run a list for me, or give me a link to a related technical paper or reference?

As Mike mentioned (I think) you might want to refer to the Apple ColorSync developer’s guide for ColorSync (www.apple.com/developer). In there is a description of all the things ColorSync does as well as what a CMM does.

The line between the functions of a CMM and of a CMS (color management system, like ColorSync) is a bit blurred.

Basically, the stripped-down function of a CMM is:

  • create color transformations (called color worlds in ColorSync). This is when you hand the CMM two (or more) profiles and it stitches them together in RAM, readying them for doing transformations. This is where the rendering intent, calculation resolution, etc are set. The creation of a transformation usually involves resampling of the profiles’ LUT data to create a 3D (or n-D) table of transformation numbers. This is very similar to creating a device link profile in RAM.

  • transform colors - you hand the transformation a list of colors or an image and it converts them from the source space to the destination space. In performing the conversions the CMM finds the closest table entries for each color and then uses interpolation algorithms to calculate its output value. How much oversampling occurs in step 1 and which algorithm is used in this step can affect the quality of the conversion and the amount of time and memory it takes.

  • some CMM’s (like Adobe’s) add the function of matching black points and scaling the output black point for optimal image contrast (black point compensation).

I think that’s about it in a nut shell. There are probably other functions but that’s the primary use. The CMS adds all sorts of other functions to this including: finding all installed profiles, opening & altering profiles, building of device links, creation of named color profiles, etc.

Regards,

Steve


o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX


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So how does one go about utilizing different CMMs?
Various applications (like Adobe Photoshop) give you the option of choosing different CMMs, but there are generally only a few defaults available, even when more are installed. For example, on my workstation at work (winXP) I have an Onyx RIP (with the GM Logo CMM), various Adobe apps (with ACE), and Monaco Profiler (monaco CMM); yet in all of these apps (and windows) only the default CMMs are available. Is this just because these companies want the end user locked into using their product? And are there any other (cheaper) options for experimenting with different CMMs?

or am I missing something painfully obvious?

At 6:35 AM -0700 9/21/05, jkotz wrote:

So how does one go about utilizing different CMMs?
Various applications (like Adobe Photoshop) give you the option of choosing different CMMs, but there are generally only a few defaults available, even when more are installed.

right…

For example, on my workstation at work (winXP) I have an Onyx RIP (with the GM Logo CMM), various Adobe apps (with ACE), and Monaco Profiler (monaco CMM); yet in all of these apps (and windows) only the default CMMs are available.

yeah, the days of multiple OS-level CMMs seem to be gone for now. I’m not sure I ever heard of any other than ICM available for Windows but Kodak may have been. Otherwise CMMs tend to be embedded into apps and RIPs and sometimes you get the chance to specify either the embedded one OR the OS-level ones. Mac OS X left all the 3rd party OS-level CMMs behind as well.

Is this just because these companies want the end user locked into using their product? And are there any other (cheaper) options for experimenting with different CMMs?

there are not really too many options as they are either embedded or you have to grab code and write it into something.

That and the experimentation may lead you to a CMM you like but can’t use in your workflow.

Regards,

Steve


o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX


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Well, that’s about what I expected, but thought I’d ask for some clearer info. Thanks for the reply Steve.