I will take a moment to correct myself. The pro8mm 50D is from Kodak NOT Velvia - man I have a lot to learn. Now that I think about it, I ike natural color reproduction as opposed to that too saturated look of Velvia. It looks cartoonish to me. I know all you cinematographers are sighing right now!
Actually, I agree with you that Velvia is too saturated. That's why I like 500t and 200t. They have a saturation level between 64t and Velvia 50. With Velvia, every piece of foliage looks like moss, it's so eye popping green.
As far as your question about 500t indoors, you could elect to shoot it with whatever light is available but to get good results you must 1) have a fast shutter (>180) and 2) you will have to keep your aperature large which may result in grainy and soft footage. I use a 1250W Photoflood kit with (2)500W and (1)250W lamps and depending on how I arrange my lighting, I can set my aperature as small as F16. I usually don't like to set it that high, but it's nice to have that sort of range. The same lighting setup with 64t would only yield somewhere between F5.6 and F8 minimum aperature. I also have a camera with a 220 degree shutter so I really do prefer the low-light capabilities. The grain increase of 500t is not as bad as some would have you believe, as long as you realize that you still do need a realistic amount of light. I would not recommend shooting this stock indoors to tea light candles or something like that.
Thanks for the encouragement for the Matte box and good luck with your shooting!