Hi, I'm trying to use my MacBook Pro to send calibration patterns to an HDTV over a TB->HDMI cable. These patterns are to be read from the screen using a DTP-94 and ColorHCFR, a free display calibration tool. However, it's essential that these patterns reach the HDTV unmodified, and as far as I'm aware OS X applies a display profile to all outgoing video signals. As a result, the video patterns would differ from what was expected and so the calibration would be affected. So, first question: am I right in assuming that a display profile is always applied? OS X seems to assign a generic profile no matter what I do, but maybe it simply acts as a passthrough? Second question: if I'm right and OS X always assigns a modifying display profile to any given display, is there any way of disabling it, even temporarily? Thanks.
I doubt a display profile is applied to a video signal on the Mac? If you open the profile that you think is used to manage the signal, in ColorSync Utility, if you find the VCGT does not have linear curves, I would say you have a case. But I have my humble doubts. If you want to be sure no transform occurs, select a generic profile like sRGB which does not contain any calibration to my knowledge. An alternative is to run the software from a different OS... Best / Roger -----Original Message----- From: colorsync-users-bounces+graxx=videotron.ca@lists.apple.com [mailto:colorsync-users-bounces+graxx=videotron.ca@lists.apple.com] On Behalf Of sirquijote@lavabit.com Sent: Thursday, January 3, 2013 11:57 PM To: colorsync-users@lists.apple.com Subject: Disabling colour management for a display Hi, I'm trying to use my MacBook Pro to send calibration patterns to an HDTV over a TB->HDMI cable. These patterns are to be read from the screen using a DTP-94 and ColorHCFR, a free display calibration tool. However, it's essential that these patterns reach the HDTV unmodified, and as far as I'm aware OS X applies a display profile to all outgoing video signals. As a result, the video patterns would differ from what was expected and so the calibration would be affected. So, first question: am I right in assuming that a display profile is always applied? OS X seems to assign a generic profile no matter what I do, but maybe it simply acts as a passthrough? Second question: if I'm right and OS X always assigns a modifying display profile to any given display, is there any way of disabling it, even temporarily? Thanks. _______________________________________________ Do not post admin requests to the list. They will be ignored. Colorsync-users mailing list (Colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx@videotron.ca
On Jan 3, 2013, at 11:56 PM, sirquijote@lavabit.com wrote:
So, first question: am I right in assuming that a display profile is always applied? OS X seems to assign a generic profile no matter what I do, but maybe it simply acts as a passthrough?
Adjustments from the actual ICC profile are applied by applications which choose to do so, but not globally.
Second question: if I'm right and OS X always assigns a modifying display profile to any given display, is there any way of disabling it, even temporarily?
I believe you may be confusing Video Look Up Table data flashed to the video card (which can be stored in a special tag in an ICC profile, and can be applied with the profile, as the Mac OS will do, if you choose a profile that has LUT data included) with the profile itself. What you need to do is be sure you are using a display profile with no LUT data, so that the data won't be adjusted at the video card level by the LUTs on its way through. But this only applies to data running through a video card, as it does to a computer display. Selecting a generic profile such as sRGB will assure that there is no LUT data being applied at the video card. C. David Tobie Global Product Technology Manager Datacolor 5 Princess Road Lawrenceville, NJ 08648, USA 609.924.2189 www.datacolor.com Phone: 207.685.9248 Mobile: 207.312.0448 Fax: 207.685.4455 Email: cdtobie@datacolor.com Skype: cdtobie
Sent from a touch-screen device On 4 Jan 2013, at 16:48, C D Tobie <cdtobie@mac.com> wrote:
On Jan 3, 2013, at 11:56 PM, sirquijote@lavabit.com wrote:
So, first question: am I right in assuming that a display profile is always applied? OS X seems to assign a generic profile no matter what I do, but maybe it simply acts as a passthrough?
Adjustments from the actual ICC profile are applied by applications which choose to do so, but not globally.
Aha, I think I understand my mistake now. When I select a colour profile for my display (say, a Cinema Display) it simply acts as a reference for colour-managed applications. That is, an application (eg. Pixelmator) can refer to my colour profile settings for a given display and if there's a profile assigned it'll modify its rendering accordingly. I think what was confusing me was that the Finder and the UI are colour-managed, and when I saw the desktop picture, menu bar and other UI elements changing with selection of a colour profile it's because the underlying software was altering its rendering, not because the OS was modifying ALL output to the display. Am I right?
Second question: if I'm right and OS X always assigns a modifying display profile to any given display, is there any way of disabling it, even temporarily?
I believe you may be confusing Video Look Up Table data flashed to the video card (which can be stored in a special tag in an ICC profile, and can be applied with the profile, as the Mac OS will do, if you choose a profile that has LUT data included) with the profile itself. What you need to do is be sure you are using a display profile with no LUT data, so that the data won't be adjusted at the video card level by the LUTs on its way through. But this only applies to data running through a video card, as it does to a computer display. Selecting a generic profile such as sRGB will assure that there is no LUT data being applied at the video card.
Aha, I get this too. So, wouldn't I be best choosing HD 709-A for the HDTV, as this is what I'm attempting to calibrate the screen to? Or am I simply entirely wrong in thinking that any video playback software (eg. DVD Player, QuickTime) in OS X is ICC-profile aware? In which case, as you say, so long as the graphic card's LUT is untouched I've got nothing to worry about in the first place?
C. David Tobie Global Product Technology Manager
<image003.gif>
Datacolor 5 Princess Road Lawrenceville, NJ 08648, USA 609.924.2189 www.datacolor.com
Phone: 207.685.9248 Mobile: 207.312.0448 Fax: 207.685.4455 Email: cdtobie@datacolor.com Skype: cdtobie
participants (4)
-
C D Tobie
-
Roger Breton
-
sirquijoteï¼ lavabit.com
-
SQ