Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: The theater went dark this morning as RealD (NYSE: RLD) shares fell 12% in trading.

So what: Today, 3-D technology company RealD wasn't as exciting after a disappointing 3-D box office this weekend. BTIG analyst Rich Greenfield said only 36% of theater attendance this weekend was at 3-D movies, worse than last year.

Now what: We may be sorting out the point when we've saturated the market with everything 3-D. Consumers just aren't willing to pay extra money to bring the kids to Kung Fu Panda 2 in 3-D when the "wow" factor isn't there. Box office hits like Avatar will continue to be in demand in 3-D but not every movie fits that bill.

Today's move shows the real difference between RealD and premium 2-D or 3-D operator IMAX (NYSE: IMAX), which is up today. I have made IMAX my top stock pick for 2011 partly because it can benefit no matter whether 3-D catches fire or not. I still like RealD's business, but the stock may have gotten ahead of itself for now.

Interested in more info on RealD? Add it to your watchlist.

Fool contributor Travis Hoium owns shares of IMAX. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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