Desire Fixtures Don't Use the Same Emitters
Two or more Source Four LED, Desire, or Colorsource fixtures, given the same DMX data, do not use the same emitter mix when outputting light. This can be seen when looking into the front of the fixture.
Description/Explanation of Issue
While ETC sources LED emitters from their manufacturers that are as consistent as possible in their output, there may still be slight variations from emitter to emitter, which can sometimes be perceived by the human eye. To compensate for these natural variations, ETC calibrates each fixture by measuring the light output from them during the manufacturing process and writing that data back to the fixture. This means that when in a calibrated mode, two fixtures with different calibration data may use a different emitter mix to get to the same RGB or HSI color point. While the emitter mix may be different, the light output of each fixture will be the same.
All Source Four LED and Desire fixtures (except Series 1 Tungsten and Daylight), as well as Colorsource fixtures of all types with software version 1.4 or higher, can be put into Direct mode. This allows you to directly control the LED emitters of the fixture without using the calibration data. You may want to use Direct mode to create specific color mixes. Keep in mind that since Direct mode is uncalibrated, giving two fixtures the same color data may result in visible differences between their light output.