Moses said:
"The Farnsworth Lantern I would suspect is more aviation/practical than the Holmes Wright - but I wonder how both compares to the real flying environment?"
Frankly the Holmes Wright test is a complete farce - at least in the way the CAA administers it at Gatwick. I'm one of those people that has no actual problems with colour vision in real life, only when doing colour vision tests, and having failed the Ishihara plate test I went for a lantern test.
The test commenced in a windowless room, in fluorescent light. As soon as I got one red/green combination wrong, that was the test finished - they stop on the spot and go no further (despite you having paid 28 quid for a whole test).
The only restriction on my pilot's licence is that I'm not allowed to fly at night because of my colour vision deficiency. I have an IMC rating, so I can fly in cloud (in the UK, at least), I just can't fly at night.
I'm allowed to fly VMC in the day, even though I'm officially unable to tell the difference between a red light and a green light being shone at me by an ATCO (actually in real life I can see the difference, with no problem). Yet I'm not allowed to fly at night even though the JAA/CAA's official test has never actually shown whether or not I'm able to tell the difference between colours at night (again, in real life I can see the difference - I've been out at night with my instructor several times just for the fun of it and the light thing is easy). All the CAA knows is that I'm unable to see tiny pinpricks of light from the far end of a room in fluorescent light - hardly an environment I'm likely to encounter in the sky.
D.