Re: colorsync-users digest, Vol 2 #558 - 18 msgs
Re: colorsync-users digest, Vol 2 #558 - 18 msgs
- Subject: Re: colorsync-users digest, Vol 2 #558 - 18 msgs
- From: "Nick Milley" <email@hidden>
- Date: Wed, 3 Oct 2001 15:17:16 -0400
In a message dated Wed, 3 Oct 2001 11:32:14 EDT, email@hidden
writes:
>
Its built on a chip; photons of light are filtered to the sensors on the
>
chip, and XYZ readings are determined on board from those light samples. It
>
certainly needs (and gets) testing prior to shipment, but other than the
case
>
coming open later and allowing light in where it shouldn't be, there's not
>
much that can change once a unit has passed initial testing.
While the electronics do not age, there are many areas that can throw a
colorimeter out of calibration. First of all, the device is an assembled
physical package. Even the smallest changes in the mechanical assembly (on
the order of .001") will cause deviations in luminance measurement. Simply
handling the device over the period of twelve months is enough to cause some
shifting of the pcb, the filter assembly, suction cups, etc. Secondly, these
devices are mounted to the screen by suction cups. The elasticity of these
components fatigue with time causing changes in the distance from the
screen. Repeatability is affected. Finally, filters age, dust collects on
diffusers, and heat causes thermal stresses.
In short, any device with a specification of high accuracy should be
recalibrated annually to certify its performance. Then again, maybe this is
why the Spyder does not need it.
Regards,
Nick Milley
Sequel Imaging