Maybe this is old news, but I just bought some el-cheapo cans with gel frames and 150w bulbs, and the space between the frames and cans (so the gels don't melt) allowed a lot of white light leakage. Not good. After some study, I masked the front of the bulb with a 4" diameter piece of paper, masked the socket threads, and painted the bulb with some high temperature BBQ grill spray paint. It took care of about 95% of the problem.