Black Point Compensation

Good morning

Thank for weel explained answer.

I understood.

But, when we use perceptual we have all color changed, when we use colorimetric, all colors inside gamut is not changed (transformed), am I right?

How Relative and Absolute Colorimetric is used to have contratual proofs for impression, if I use perceptual, I have a different aproach to this situation and I do not get my proposal to have transformed only color out of gamut.

Am I right?

Thank you

First things first, I have my grandchildren here today and tomorrow so my (sane) time is limited. I'll give a rough overview then in the next few days get you some documentation. 

I'm not sure what your native language is and I only have the definitions in U.S. English. I must admit even if English is your native language most people need to read the definitions several times and then still need help understanding them.

There are 4 rendering intents: 

Saturation (I have never seen a workflow where it was valid) does as it says it over saturates the conversions.

Absolute Colorimetric, used for hard proofing, it does well if proofing a newsprint job on gloss or matte paper. It will always try and print a gray color to simulate the white point of the destination, ergo the prints always have a frame around them to simulate the destination paper.

Perceptual rendering, the only profile created for converting large color spaces into small color spaces. Such as Prophoto RGB to Adobe or sRGB, or any RGB color space to any CMYK color space.

Perceptual is the default rendering intent for almost all ICC profiles that are not device dependent print color profiles. Yes the colors change but all colors in the source are represented in the destination in a proportional manner so the result looks as much like the original as possible for the destination gamut. Yes out of gamut colors change but they rarely posterize.

Relative Colorimetric rendering is really only good at converting color spaces of very near or equal sizes. It has no value for converting wide gamut spaces into small gamut spaces. 

No relative colorimetric does not leave unchanged source colors that are in gamut in the destination space. Mathematical changes do take place differently for source colors that are in gamut for the destination space then for source colors that are out of gamut for the destination space. THAT'S the PROBLEM.  In wide gamut to small gamut conversions a very few colors get little change and a very large amount of colors get a radical change. Causing distortion and posterization.

Many RGB color spaces are vastly larger then CMYK color spaces, Prophoto RGB is so much larger than sRGB that conversion to sRGB from Prophoto in many cases using relative colorimetric causes severe distortion and posterization.

The above rendering intents ARE ICC COMPLIANT! The below discussion is not ICC Compliant. 

Relative Colorimetric with Black Point Compensation turned on IS NOT ICC COMPLIANT!

Black Point Compensation turned on only works with Relative Colorimetric Rendering by design. It mimics Perceptual Rendering but it very slightly different. 

Do a test!  Take a colorful RGB image and duplicate it twice. Convert all three images to the same CMYK profile one with perceptual rendering, the nest with Relative colorimetric with black point compensation TURNED ON, then convert the third image with Relative colorimetric with black point compensation TURNED OFF and compare them in Photo-PAINT simultaneously. 

There are two basic errors made in the default installations by Adobe and Corel.

Adobe should have stopped using relative colorimetric rendering with black point compensation turned on 20 years ago. It has not been needed for that long.

When Corel changed to a professional color management process with the release of version X5 they should not have had relative colorimetric rendering with black point compensation turned off as their set default.

Both applications should default to perceptual rendering.

Adobe has made cross application color management difficult because they support very few, to only their color engine and they stopped releasing a 64 bit version of Adobe Color Engine (ACE) for others to use. To ad insult to injury their steadfast use of relative colorimetric rendering with black point compensation turned on.

Corel at least supports multiple color engines, although they need to set their default to perceptual rendering. 

Now that the grandchildren are gone and sanity is returning I took the time to update my reading of the ICC (International Color Consortium) specifications and white papers. I have downloaded pertinent content and will place on line for you to download if you wish.

The truth is that reading all that data is as complicated and confusing as the Unabomers Manifesto. Confusing logic to say the least.

Color management while being an evolving technology is has been significantly mature for well over a decade.

I find it best to keep discussions sectioned into three major categories.  Those who calibrate manufacturing devices. Those who are high end color critical work creators. Those who simply need basic settings for specific tasks.

For those like me who calibrate equipment the software and specifications have improved for greater accuracy.  However, the question as always is, has it exceeded demand and general capability? 

I regularly see the physical aspects of calibration being ignored so often that the reality is that with all the software improvements there is no real-world improvement. 

For those who simply need to complete standard acceptable color tasks, again things haven't really changed.

Acceptable color standards have lowered so you may need to adapt, the great color that you print may look awful on the web or for display.  Yes, there is a significant difference, display applications such as those for presentation view vastly different than web browsers.  Web browsers are really bad.

I suggest that such a file creator buy medium priced displays, more like the average viewer of your work may purchase.

I suggest in CorelDRAW that you use a standard web-based color management setting, customize to use perceptual rendering and save it. 

Have fun and make money.

For those who do color critical work things have made very modest improvements. The newer specifications have resulted in a higher degree of repeatability in color. There are also now a very modest proliferation of 16 bit RGB output devices available. 

With this said most things have remained the same and that in my opinion is a good thing.

You need to build a light controlled studio environment so you are viewing your display properly. A 2 degree light angle, 5,000 or 6,500 Kelvin light source. Heavy drapes or no windows to control ambient light.

You need to purchase color calibration equipment, for display only an Xrite Spyder Elite will work. More intensive work I use an I ONE system.

You will need a display capable of displaying at least 98% Adobe RGB color space. There is a significant difference between setting up a display for color managed working creating a file for color managed work. Benq make nice 20" displays for about $900 U.S., ViewSonic has 27" units for a bit over $1,000 U.S., there are others where the sky's the limit. $40,000 video models.

A display requires a custom ICC profile it should be as wide a gamut as possible. My ViewSonic exceeds Adobe RGB.

A graphic application RGB color profile should NEVER be set to a display specific ICC profile but BE SET to an industry standard ICC profile. For web, sRGB (all over the world), for press RGB regional settings apply, Adobe RGB, ECI, Japan, are samples check within you region.

CMYK profiles are regional by media, for creation applications NOT SPECIFIC media but industry standard general medial types. Such as coated, web coated, uncoated and web uncoated or newsprint.

Calibrating you display for the widespread gamut possible, setting the creation applications to industry standards both RGB and CMYK and working in a controlled well-lit environment allows the most repeatable color in a global working environment.

This allows you to create in controlled conditions, providing files for output that are created within parameters that the output devices are designed to work within. This allows the final output conversions to be repeatable and pleasing.

As far as application color management Adobe has continued to do as they please their users are stuck with their color engine and mind set. They only provide compatibility with Adobe products. Relative Colorimetric with Black Point Compensation turned on is not Relative Colorimetric rendering, (in fact it's much closer to Perceptual Rendering) and unfortunately is the Adobe default. 

Black Point Compensation is not supported by all applications and when it is supported it may or may not be supported identically in all the applications. 

CorelDRAW has poor defaults, it sets Relative Colorimetric as a default rendering. In fact, a 2007 ICC white paper states that Relative Colorimetric Rendering without Black Point Compensation has little to no value and I agree.

As file creators and designers, we must understand that those who view the end result of our work DO NOT measure color they PERCEIVE color. The Perceptual Rendering intent perceives color like we perceive color. That point is what makes Perceptual Rendering a valuable tool.

Changing that to Perceptual Rendering is ICC Compliant, is much closer to the Adobe default and is supported everywhere by everyone so universally you have better control over your output. 

CorelDRAW supports multiple color engines. If getting as close to Adobe conversions as possible is what you want, I suggest using LCMS as your color engine.

I use WCS because in a Windows system all RGB for the display must be handled by WCS, it's built into Windows. For me it reduces the number of conversions and a 1- or 2-point difference is invisible.

The reality of the evolution of color management for the file creator for the last 5 years is that very little has changed. I only see that very high-end inkjet work has progressed in a manner useful for designers.