Shares in both companies are up slightly in early trading after they announced the expansion of their revenue sharing agreement. It will raise the number Regal’s IMAX venues to 87. The change is a key part of Regal’s “strategy to offer premium moviegoing experiences to our customers,”  CEO Amy Miles says. Regal is taking a two-pronged approach to large-screen theaters, where the company hopes to benefit from premium ticket prices: In addition to its arrangement with IMAX, it’s building its own RPX: Regal Premium Experience sites. That’s led some analysts to wonder whether IMAX is running out of domestic growth opportunities. IMAX chief Rich Gelfond says that the new agreement shows that the company has “continued growth opportunities in the North American market, including strong demand in areas within and outside of large cities.”