Datacolor User to User Support Group.

>>Shouldn't the Spyder give a near identical reading of ambient regardless of which computer is driving it?

Where are you getting ambient light readings in Candelas?
 
>>Shouldn't 128, 128, 128 produce the same apparent image on all three displays instead of obvious chromatic differences?

Yes, it should, but these are different screen types, both in gamut, and in viewing angle. The gamut difference means your whites and grays are being constructed from more saturated RGBs with the desktop displays. The viewing angle means that the Spyder is reading colors that vary more with angle on the laptop. 

These factors add up to a difference to your eye. You could calibrate the laptop to a custom whitepoint in order to achieve a more acceptable visual match, if side-by-side use is the goal, but laptops are generally calibrated to native luminance (and maybe even native whitepoint) for use in uncontrolled environments. 
 
In my experience, Dell laptops are among the must challenging screens to calibrate; matching, say, Apple Cinema displays to a MacBook produces a much closer visual result. 

C. D. Tobie
Global Product Technology Mngr.
Digital Imaging & Home Theater
Datacolor.com
CDTobie@Datacolor.com

On Oct 23, 2010, at 10:11 PM, Jim Miller <jim@...> wrote:

> Shouldn't the Spyder give a near identical reading of ambient regardless of which computer is driving it?
>  
> Shouldn't 128, 128, 128 produce the same apparent image on all three displays instead of obvious chromatic differences?
>  
> FWIW, the desktop displays have a gamut pretty close to AdobeRGB according to S3Elite software 4.02.
>  
> The laptop is limited to approximately sRGB according to S3E 4.02