Re: Two Displays, One Graphics Card, Two Profiles, Which Profile wins?
Re: Two Displays, One Graphics Card, Two Profiles, Which Profile wins?
- Subject: Re: Two Displays, One Graphics Card, Two Profiles, Which Profile wins?
- From: Steve Upton <email@hidden>
- Date: Fri, 4 Feb 2005 09:26:49 -0800
At 11:08 AM -0800 2/3/05, Andrew T. Lynch wrote:
>Hi Folks,
> I have an 20" Apple Cinema Display (DVI) and a 17" Apple Studio Display (ADC) plugged into the Radeon 9600 on my G5 2.5DP. I have profiled each of them with a Gretag Macbeth Eye-One Display (Version 1). I used a (not native) white point of 6500, a gama of 2.2 and a luminance of 140 for both profiles.
>
>After profiling, the two displays still look different. I have a the same photo as a background on both displays, and the colors are slightly different.
right... well... let's talk about that a bit. If you are talking about desktop pictures I'm not sure that the OS color manages them. For testing I recommend opening an image in Photoshop. Then open a second window for the image and pull this window over to the 2nd display. THEN you will be working correctly and be able to evaluate the images.
remember, calibration affects all graphics going to a display but the app displaying an image has to explicitly call routines in order to have the profile applied. So calibration (gray balance, gamma, etc) may be fine but colors depend on the profile.
>From the Gretag Macbeth website:
>
>>Please note, the monitor profiling process in i1Match supports two steps: the first step is the monitor calibration, which stores an individual gamma table in the graphic card. The second step is the profile generation, which stores an individual ICC monitor profile as current system profile in the control panel "Display". If you have a dual monitor card with one graphic ship and two output signals, it is not possible to store an individual gamma table for each monitor (both monitors will be controlled by the same gamma table). But it is possible to set an individual ICC profile for each monitor in the system's control panel "Display". On dual monitor cards with one graphic chips you need to decide, which of the two monitors should be used for color critical work. However, we recommend to use a dual graphic card with two graphic chips.
>
>Is this the cause of the color difference?
This can be the case on Windows systems but it is NOT the case on Macs. I have yet to see a Mac video system - either built-in or display cards - that does not allow you to separately define calibration curves and profiles for each attached display - even if they are mirrored.
>Do I need to use the same profile for both displays? If not, how do I make sure that I am using the gamma table from the profile for the primary display (the 20" cinema display).
nope, as above
>It does appear that for some purposes the 17" display is considered the primary display. It is where the little spinning wheel appears when the system is booting. I do have the menu bar on the 20" cinema display.
this is probably because it is plugged into the primary video card which is in the AGP slot. You may also find that this card is faster (due to the AGP) and so might want to plug the larger display into it. If they are both plugged into one card, then it is the "primary display" on that card.
>As a side note, both displays are supposed to have a native white point of 6500. The 17" was measured as 5900 and the 20" was measured at 7100.
right, not uncommon.
At 1:18 PM +0100 2/4/05, Peter Karp wrote:
>
>Lower-priced colorimeters and spectrophotometers (I mean all the usual
>devices like the DTP-series, the EyeOne series, the Spyder...) use a
>not too sophisticated "filter system" which can not truly describe the
>CIE 1931 standard observer color matching functions.
In the case of spectrophotometers this is not true. Spectrophotometers do not use a filter system but rather use the actual CIE standard observer curves. In the case of colorimeters, this is correct.
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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