April 2016 - colorsync-users

3D LUT Creator
by Roger Breton 21 Apr '16

21 Apr '16

I'm getting my feet wet into broadcast video calibration these days and I stumbled upon this quite surprising piece of software which, to me, boasts intuitive Lab visualizations for color corrections, the kinds of tools I'd *love* to see in Photoshop - maybe it's already there and I keep missing it? Shame on me :( https://www.youtube.com/watch?v=12w0bc0S3a4 What I was particularly impressed with was the first few seconds of the demonstration where, for all intents and purposes, an ICC-type of "Media White Point" edit is made very intuitively by directly manipulating an "a/b grid" point similar to what the Gradient Mesh tool does in Adobe Illustrator. / Roger Breton

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RE: Sending CMYK data to PS Printer
by Roger Breton 08 Apr '16

08 Apr '16

We have a 7800 at school and this is a CMYK device, the driver is not RGB. But you need to turn color management off to get what you want in the driver's printing option. Works like a charm. / Roger -----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com [mailto:colorsync-users-bounces+graxx=videotron.ca@lists.apple.com] On Behalf Of Lorenzo Ridolfi Sent: 7 avril 2016 10:40 To: colorsync-users(a)lists.apple.com Subject: Sending CMYK data to PS Printer Hi, I’m working with a Xerox Phaser 7800 with no RIP, using the default Xerox driver. Does anybody know if Acrobat sends the PDF data as CMYK to the PS driver by default? I’m afraid the driver may convert the CMYK data to RGB. Is any way to check if the data sent to the printer is really CMYK? I’m thinking in printing CMY versus K values to check. Thanks, Lorenzo _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx(a)videotron.ca

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gamma bewilderment wrt/ Argyll’s documentation
by Uli Zappe 07 Apr '16

07 Apr '16

Hi, I’ve stumbled about the following passages in Argyll’s documentation for dispcal (http://www.argyllcms.com/doc/dispcal.html) > -g gamma Set the target response curve gamma. This is normally an exponential curve (output = input ^gamma), and defaults to 2.4 on MSWindows and Macintosh OS X 10.6 or latter and Linux/Unix (which is typical of a CRT type displays real response), and 1.8 on a Macintosh (prior to OS X 10.6). > [...] > Also note that many color spaces are encoded with, and labelled as having a gamma of approximately 2.2 (ie. sRGB, REC 709, SMPTE 240M, Macintosh OS X 10.6), but are actually intended to be displayed on a display with a typical CRT gamma of 2.4viewed in a darkened environment. This is because this 2.2 gamma is a source gamma encoding in bright viewing conditions such as a television studio, while typical display viewing conditions are quite dark by comparison, and a contrast expansion of (approx.) gamma 1.1 is desirable to make the images look as intended. There are 3 things here which I don’t understand: 1. Where do some of the default gamma values come from? In the Mac OS X 10.6 release notes (https://developer.apple.com/library/mac/releasenotes/MacOSX/WhatsNewInOSX/A…) Apple clearly stated that the gamma is now 2.2 (not 2.4, as the Argyll doc says): > Historically, the default gamma correction for Mac OS has been a value of 1.8 (a useful value for print professionals). In recent years, television, video, and web standards have all settled on a default gamma of 2.2. In OS X v10.6, the Mac moves to this common standard Later, Apple has repeatedly confirmed this. It is true that when Apple talks about gamma 2.2, they actually mean the sRGB TRC. You can verify this by looking at the OS X supplied, so-called "Generic Gray Gamma 2.2 Profile" (/System/Library/ColorSync/Profiles/Generic Gray Gamma 2.2 Profile.icc) which Apple introduced with Mac OS X 10.6 and which actually sports an sRGB TRC. But while it is true that the gamma curve *part* of an sRGB TRC is 2.4, you certainly cannot say that the sRGB TRC as a whole is “gamma 2.4". It’s either "sRGB" or (simplified) "gamma 2.2" (gamma 2.239, to be exact). That is all the more confusing since the Argyll documentation correctly reports the pre-10.6 gamma value as being 1.8, in accordance with Apple. In the same vein, the simplified gamma TRCs of REC 709 and SMPTE 240M are 1.961 and 1.932, respectively, and certainly not gamma 2.2, as the Argyll documentation says. These might be trivial documentation errors, but they gain importance with my 2 additional (following) problems. 2. Why does the documentation assume that a color appearance adjustment (= contrast expansion of gamma 1.1) is desirable by default? Video production is a very specific case, and it’s not clear from the documentation whether the "bright viewing conditions such as a television studio" refer to the recording or the editing environment. If the former, this is certainly a gross generalization, since the recording environment can be anything from a sunny beach to a dark and stormy night. If the latter, I very much doubt that a typical TV editing environment is *brighter* than the typical office environment in which a computer is typically used. But even more importantly, with a few specific exceptions, the task of color management is to preserve the colors as set by the artistic intent of the editor in the *output referred* color space, not the actual colors of the source image, anyway. So the colors of the recording environment do not really matter. Additionally, as I already wrote, video is a very specific case for color management on a computer. By far the most typical case will be that the colors of some illustration or image should be preserved on their way from the editor to the consumer. There may be all kinds of editing and viewing environments, but I fail to see how in a statistically significant way the typical viewing environment will be darker than the typical editing environment. Therefore, I don’t understand how a color appearance adjustment can be assumed to be desirable by default. 3. Why should the user care about the TRC at all in a color managed environment? This is the point that baffles me most. The whole point of color management is reliable reproduction of colors *independent of* the specific underlying technical parameters in hardware and software. This means that in a color managed environment, choosing a different gamma value for a display calibration should ideally have no visible impact *at all*, since (assuming a corresponding monitor profile) the CMM is supposed to compensate for different TRCs of source and destination. (I assume ideal hardware and software here and disregard real-world technical limitations such as hardware specs and limited bit depth, as they are not the point in this context). So if I calibrate my display to gamma 1.8 or gamma 2.4 should be completely irrelevant for the visual results I get as a user, as long as all my applications and the GUI of the operating system are color managed. On an ICC color managed computer, this means that a) using a higher gamma could not even achieve the desired contrast expansion described in point 2) above and that b) there should be no reason to recommend any specific gamma value to the user at all (whereas Argyll’s documentation makes a lot of specific recommendations). In contrast, as I understand it, the only ICC color management compatible way to achieve a color appearance adjustment (= contrast expansion, as far as the suggestions in the Argyll doc are concerned) is to build a color appearance adjusted monitor profile. Does anyone share my confusion, or can dispel it? Bye Uli _________________________________________________________________________ Uli Zappe, Christian-Morgenstern-Straße 16, D-65201 Wiesbaden, Germany http://www.ritual.org Fon: +49-700-ULIZAPPE Fax: +49-700-ZAPPEFAX _________________________________________________________________________

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Sending CMYK data to PS Printer
by Lorenzo Ridolfi 07 Apr '16

07 Apr '16

Hi, I’m working with a Xerox Phaser 7800 with no RIP, using the default Xerox driver. Does anybody know if Acrobat sends the PDF data as CMYK to the PS driver by default? I’m afraid the driver may convert the CMYK data to RGB. Is any way to check if the data sent to the printer is really CMYK? I’m thinking in printing CMY versus K values to check. Thanks, Lorenzo

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CIELab colorspace
by Ricardo Decastro 07 Apr '16

07 Apr '16

Hey anyone know why the original CIELab color space is shaped like a 'horseshoe'? please help -- *Ricardo Decastro* *810 West Maude* *Arlington Heights IL 60004* *312.560.9511* sendricardo(a)gmail.com

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Gamut mapping newbie question
by Roger Breton 05 Apr '16

05 Apr '16

I am told that, gamut mapping only occurs when the Source and Destination gamuts are of different sizes and shape? Best / Roger

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RE: gamma bewilderment wrt/ Argyll's documentation
by Roger Breton 02 Apr '16

02 Apr '16

I have nothing against Eizo, they're good monitors, but not all monitor manufacturers force their users into low Luminances ranges to comply with warranty. If you need higher luminance levels while staying within warranty, look at NECs. / Roger -----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com [mailto:colorsync-users-bounces+graxx=videotron.ca@lists.apple.com] On Behalf Of Uli Zappe Sent: 1 avril 2016 15:22 To: Bob Frost <bobfrost(a)btopenworld.com>; ColorSync List <colorsync-users(a)lists.apple.com> Subject: Re: gamma bewilderment wrt/ Argylls documentation Am 01.04.2016 um 10:08 schrieb Bob Frost <bobfrost(a)btopenworld.com>: >> From: Graeme GillSent: Friday, April 1, 2016 1:19 AM Many print >> professionals deliberately calibrate their displays to a lower brightness such as 100 cd/m^2 and adjust their surround accordingly,................................................................ ................. > Just adding another point against high brightness monitors, But Im not saying nobody should use a dim environment. Im only saying a dim environment is not *typical* for computer usage, and therefore should not be assumed for the *default* color management configuration. If professionals want to work in a dimmer environment for whatever reason, being professionals they should be able to adjust the default configuration accordingly. > even my latest Eizos can only be used at 100 cd/m2 to keep within the warranty. Which is a strange limitation indeed. OTOH, if the target group is willing to spend $$ for a product with such a limitation, why not? ;-> Bye Uli _________________________________________________________________________ Uli Zappe, Christian-Morgenstern-Straße 16, D-65201 Wiesbaden, Germany http://www.ritual.org Fon: +49-700-ULIZAPPE Fax: +49-700-ZAPPEFAX _________________________________________________________________________

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RE: gamma bewilderment wrt/ Argyll’s documentation
by Roger Breton 01 Apr '16

01 Apr '16

What about Certification? Isn't ISO-3664 condition P2 calling for 160 cd/m2? Just curious about your experience. / Roger -----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com [mailto:colorsync-users-bounces+graxx=videotron.ca@lists.apple.com] On Behalf Of Bob Frost Sent: 1 avril 2016 04:09 To: graeme(a)argyllcms.com; colorsync-users(a)lists.apple.com Subject: Re: gamma bewilderment wrt/ Argyll’s documentation From: Graeme Gill Sent: Friday, April 1, 2016 1:19 AM Many print professionals deliberately calibrate their displays to a lower brightness such as 100 cd/m^2 and adjust their surround accordingly, ................................................................................. Just adding another point against high brightness monitors, I'm only a print amateur, but I calibrate my Eizos to 80 cd/m2, since the Eizo warranty of my older displays is void if used at higher brightness, while even my latest Eizos can only be used at 100 cd/m2 to keep within the warranty. Bob Frost _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx(a)videotron.ca

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While on the subject of sRGB...
by Roger Breton 01 Apr '16

01 Apr '16

I know all you Mac afficionado will want to clobber me with my < PC > stories but, as I was characterizing my SurfacePro3 with i1profiler and the i1pro2 here, today, while looking at the resulting profile in good old ColorThinkPro3, I was surprised to find an almost exact match, gamut wise, between this display and the sRGB profile. To tell you the truth, I got 350+ cd/m2 @ 7259K, a little too "blue" for my taste. / Roger

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RE: Gamut mapping newbie question
by Roger Breton 01 Apr '16

01 Apr '16

Thank you Dr. Derhark. / Roger -----Original Message----- From: Max Derhak [mailto:Max.Derhak@onyxgfx.com] Sent: 1 avril 2016 13:48 To: Roger Breton <graxx(a)videotron.ca>; ''colorsync-users?lists. apple. com' List' <colorsync-users(a)lists.apple.com> Subject: RE: Gamut mapping newbie question Roger, Generally, for cases utilizing Dumb/static CMM ICC processing: Gamut mapping occurs when the application of the Source profile results in a Profile Connection Space (PCS) color that is outside the gamut of the destination profile, and gamut mapping is provided by the destination profile. Gamut mapping is not needed when the resulting PCS color is inside the gamut of the destination profile. Thus, gamut mapping is not performed for PCS colors within the intersection of the source and destination gamuts. Additionally, destination gamut colors outside of the source gamut are not accessed. For cases utilizing a Smart/Dynamic CMM: It is possible for the CMM to perform rendering/re-rendering along with gamut mapping by taking into account both the source and destination gamuts to achieve various reproduction aims. In this case mapping between non-intercecting regions of the gamuts is possible. However, the extent to which this happens is a proprietary aspect of the smart/dynamic CMM implemeneter. Max Derhak (PhD) Principal Scientist -----Original Message----- From: colorsync-users-bounces+max.derhak=onyxgfx.com(a)lists.apple.com [mailto:colorsync-users-bounces+max.derhak=onyxgfx.com@lists.apple.com] On Behalf Of Roger Breton Sent: Friday, April 01, 2016 10:41 AM To: ''colorsync-users?lists. apple. com' List' Subject: Gamut mapping newbie question I am told that, gamut mapping only occurs when the Source and Destination gamuts are of different sizes and shape? Best / Roger

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