Turns out, extended phone calls are perfect for Ganzfeld experiments (cut ping pong balls in twain, shape them to fit over the eyes, and voila--unified field of vision).
Within a minute, the visual field disappeared from perception, and because I was paying more attention to the conversation than to what my eyes weren't seeing, slow pulses of blue-violet began to well up through the otherwise colorless field.
A spectrum of green, blue and violet shifted constantly through the visual field. Occasional patterns emerged--a few times a sphere of the prettiest electric violet seemed to float up through an opening where the underside of an umbrella was perceptible.
The visuals resisted my attempt to control them, and a few other attempts brought on a quick-pulse phase, where everything was in a state of fast vibration and I knew I was only seeing the "on" moments of vision.
It's quite hard to explain a colorless field, but it is not an experience I'm likely to forget. Seeing but having the brain shut off vision and then replace the visual field with its own construction is as equally fascinating, and I'm wondering if I can, with practice, convince the brain to expand the visual field beyond the angle usually afforded by the eyes.
Having seen a 180 degree field in lucid dreams makes me very interested in attaining that state in a more easily accessible way.
Other things I noticed: moving my hand and seeing an imperfectly placed phantom of it where it would be if my vision wasn't obscured, the physical experience of the visual pulsing effects, and the ease of returning to the state after a brief interruption.
Just what can the brain do when it becomes accustomed to the Ganzfeld?