BasICColor and "vcgt" tag

I don't know if what I am saying makes any sense,

but from what I understood so far about calibrating/profiling  LCD 

monitors such as Eizo CG 21,

the best thing a calibrating/profiling soft can do is to make all the 

necessary adjustment in the monitor video card  through DDC/CI since 

it's got more bit depth than the apple video card does

Correct?

You are absolutely right.

My question is:

I created two profiles for my Eizo through an Eye-One spectrophotometer

First Profile         with Color Navigator 3.0.1  - D50  Gamma 2.2 -  

90 Cd/m2

Second Profile   with BasICColor 3.0.4   -  D50  Gamma 2.2  - 90 Cd/m2

The profile created with ColorNavigator has a "vcgt" tag  (apple 

display card table) with the RGB channels set at gamma 1.0, minimum 0 

maximum 1  - a straight line - therefore I assume the values of the LUT 

in the computer video card have not been touched

The profile created with BasICColor 3.0 has a "vcgt" tag which is not 

straight for  the 3 RGB channels,

each channel has it's individual curve/correction,

for example, blu has a minimum  value of 0,001 and maximum of 0,984

Am I wrong to assume that therefore BasICColor has changed somehow the 

values in the computer video card's  LUT?

You are right again. 

basICColor display uses a unique technique in calibrating monitors. If you have a "hardware-calibratable" monitor like the EIZO CG21, display will first measure the tonal response curve, calculate a correction curve and load it into the monitor. Then display measures the corrected values again and iterates until the deltaE values are as small as possible.

In the case of the CG21, display can only do a tonal response correction, not a gray balance in the hardware of the monitor, since the CG21 has only 1 LUT for all three channels, R,G and B. The successor, CG210, has 3 LUTs.

If display detects only one LUT, it corrects the gray balance on the graphics card, in addition to the tonal response calibration in  the monitor. If it detects 3 LUTs in the monitor, you will see a straight line in the vcgt and thus in your video card.

So, it´s not a bug, it´s a feature! basICColor display generates the most accurate calibration possible.

Best regards,

Karl Koch