by Martin » 08 Apr 2014, 16:44
That is correct, but a too long period might feel unnatural forcing of the fixation and keeping the eye lid open. It's very personal.
I typically use 800ms and got there through trial and error. Often it comes down to a trade-off between duration and number of samples.
I've noticed that if I keep my eyes fixed and open for a longer duration the soft contacts I'm wearing tends to dislocate and/or dry out whereby the glint reflection becomes less pronounced which affects detection and tracking.