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Author Topic: i1Profiler 1.4.2 CMYK profiles: warning  (Read 752 times)
yannb
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« on: January 31, 2013, 04:24:16 AM »
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Hello to you all,

There is a very confusing inconsistency in i1Profiler between 1.3.1 and 1.4.2 in the profile settings tab for CMYK profiles. The black start value and its corresponding curve do not match, and more important, it affects the way profiles are built.

In 1.3.1 a black start value of 20 meant that from 20% on, black was used. The range was 0-90. In 1.4.2, the same value means black from L*20: a huge difference. Now the range is 10-100.

Furthermore, the information displayed in the Help section is not updated. It still says that a low value introduces black from the highlights. In 1.4.2 it is the opposite.

In both versions the Y axis is K% out, and X is L*. The black start value in 1.4.2 is now more in correspondence with the curve, but it is not a standard way to represent an black separation curve.

I've googled this behaviour, but can't find anyone reporting this as well. Can anyone confirm my findings?

An email to X-Rite support is already underway...

Regards,
Yann
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yannb
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« Reply #1 on: January 31, 2013, 04:59:21 AM »
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Hello,

I've just received a reply from X-Rite tech support.

Quote

You are right, the Black Start curve option has changed the way, how it works. I have attached a short explanation, why it has changed. I also need to do some tests to understand how it acts now and here is, how I interpret it, to get some orientation, what value to select:

Samples:
-   Select a Black start of 100% to get Black into tonal CMY values from 0-100%
-   Select a Black start of 70% to get Black into tonal CMY values from 30-100%
-   Select a Black start of 50% to get Black into tonal CMY values from 50-100%
-   Select a Black start of 30% to get Black into tonal CMY values from 70-100%
-   Select a Black start of 10% to get Black into tonal CMY values from 90-100%

I will address the point, that the Help text has not been updated, to our product management. For the meantime I will create an FAQ.

End Quote

The PDF document the person mentiones is attached to my post.

What aids to the confusion, is that there are no units displayed, either next to the black start slider and on the X axis. I would add ' L* ', but who am I...

Regards,
Yann
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digitaldog
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« Reply #2 on: January 31, 2013, 09:41:15 AM »
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I would add ' L* ', but who am I...

You could be the fellow who invented the internet or the idea behind Black Point Compensation and the likelihood is, your request would not be implemented. I sometimes wonder if the people designing this product ever actually use it. The logic behind many of the 'features' and GUI is beyond me and I've tried to understand it for years.

Going back OT, in the PDF it says:
Quote
Starting in version 1.4.0, the slider for Black Start was reversed to match the curve. This has no impact on legacy files, they still work fine and can be loaded without issue

So if you drag and drop an asset built the old way, it IS honored?
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Andrew Rodney
Author “Color Management for Photographers”
http://digitaldog.net/
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