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: Shares of RealD (NYSE:RLD) plunged for real today, down by 17% at the low, after the company announced disappointing box office sales for June.

So what: The company said that box office sales in June for RealD-enabled screens was approximately $291 million, of which $158 million was domestic and $133 million was international. Revenue for the fiscal quarter should be around $838 million, of which $431 million was domestic and $407 million was international.

Now what: The June sales were down sequentially from $345 million in May, which bodes poorly considering how important the summer is for Hollywood. Consumer interest in 3-D movies may be waning, as consumers may be becoming pickier about what they watch in the format since the prices are higher. RealD received a handful of analyst downgrades today following the figures.

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

Fool contributor Evan Niu, CFA, has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.