Hi @chilinski,
>> I assume that the point at which they are the largest is the ideal distance. Is that correct?
No, in fact the nominal distance is around 30cm from the screen (About half way between the extremties) but so long as both eyes are found and within the tracking area, you should not notice any difference in calibration quality.
>> Is it better to be brighter or dimmer?
Well, generally we would recommend a dim environment, but this very much depends on the *type* of light in your area. Natural light (containing IR) can interfere with ideal trackability to try not to have the tracker particularly close to large windows or in fact facing electric spotlights. With regard to background, yes a darker background has been found to improve those in problematic cases. Overall, try to keep ambient visible and IR light to low levels if possible.
>> So I built a stand to which the 4C is attached, and that sits about eight inches in front of the monitor.
Yes, a few other customers have experiemented (With mixed results) on this kind of setup
This post @ http://developer.tobii.com/community/forums/topic/ultrawide-monitors/ might help you out in optimising your setup.
>> Thank you in advance for the previous info; that was very helpful and it might merit a write-up on your website that describes the calibration process.
You are quite welcome! Please don’t hesitate to let us know if we can be of any further assistance 🙂