U of S | Mailing List Archive | alt-photo-process-l | Re: calibrating monitor

Re: calibrating monitor

Hi both of you,
RGB numbers are pure abstract values, they are not connected to any physical devices initially. Lets say the RGB space is a cube and as I said it is an imaginary cube, your system, video card and it's default configuration have de facto assign RGB value (255,255,255) to the "white" of the screen whichever it's actual physical value (D50,D65,...). This sets a single point of our cube but not the size of each side which still need to be define. I assume your calibration device does exactly that and it must read the value you mention below for the "black point" and since this "black point" is on the diagonal of the cube, setting the black point also sets the size of each side. Why not RGB (0,0,0), basically it's simple, your monitor can't display a darker physical value then that but darker values may be printable or used. Having the true and mesured "black point" allow you to use darker values then that in the file and while you can't see it, it handle by one of the function of Color Management to take care of non-displayable value in some fashion (defined in the profile). This also allow for darker value to be used in the file and while you wont see them on your screen, they may be printable or not but they are perfectly "legal" values to use.
You can find quite a lot of info on the net on color science and color management, I find Norman Koren site to be excellent on this topic (monitor calibration) and a lot more.
Hope this helps,
----- Original Message -----
From: ender100
Sent: Saturday, July 26, 2008 2:34 PM
Subject: Re: calibrating monitor


That is odd that the CMYK values would shift after calibrating your monitor.  Calibrating your monitor doesn't change the values of the step tablet.  The RGB values remained correct though.  I only use the RGB values, not CMYK.  I think you will be fine.

On Jul 26, 2008, at 3:35:25 AM, Jusdado <jusdado@teleline.es> wrote:
Hello to all: 
Before calibrate my monitor with "Eye-One Display 2", the values RGB and 
CMYK measured in Photoshop for the Step Tablet 101 PDN were: 
White Pure: RGB=255; C=0%, M=0%, Y=0%, K=0% 
Black Pure: RGB = 0; C=100%, M=100%, Y=100%, K=100%. 
After calibrate the monitor with "Eye-One Display 2", the values RGB and 
CMYK measured in Photoshop for Step Tablet 101 PDN are: 
White Pure: RGB=255; C=0%, M=0%, Y=0%, K=0%. 
Black Pure: RGB = 0; C=95%, M=83%, Y=82%, K=90% 
1. - that has happened? 
2. - can I consider black pure the current values?. 
3. - will I have to adjust another time my curves?. 
Thank you and pardon for my English, text translates for computer.