For the few of us who are sensitive to the RainBow Effect (RBE), the speed of the Optoma color wheel comes into play. Optoma puts a 2X color wheel in the UHD51A (and UHD50). This is on the slow side, and as a result, I do see rainbows on most fast action dark scenes, when bright white objects are moving... Fortunately for Optoma, only a small percent of people are RBE sensitive. (I’ve never seen published numbers, but I would guess between 5 and 10% of the population), and people vary in terms of how sensitive they are as well.
I’m typically RBE sensitive, so I can say that I would definitely prefer a faster color wheel (such as found with competing BenQ projectors). But for most folks this is a non- issue. If you don’t know if you are RBE sensitive – this is the first DLP projector you have looked at, be sure to purchase from some reputable AV dealer with a good exchange/refund program. If it turns out you are one of us RBE types, then this projector is probably not the best choice for you. There are competing projectors with faster color wheels, and 3LCD projectors (no RBE because no color wheel), as alternates.
BTW not the worst color wheel of late. I really liked the Acer laser projector, the VL78560. It has even more rainbows, so I couldn’t own it, but I can definitely recommend that more expensive projector for those not sensitive. Same for this Optoma except that the amount of rainbows isn’t too bad – the Acer much worse.
Bottom Line: If you are rainbow sensitive, you may still really like this projector, despite the occasional rainbows. Or you may want to look elsewhere. The best news, though, is you are probably not RBE sensitive anyway.