RealD Inc. on Tuesday said it had filed a registration statement with regulators that would enable longtime shareholders to sell more than 7.8 million shares of common stock.

The Los Angeles 3-D movie technology company, which went public in July, said in the Securities and Exchange Commission filing that it would not be offering any shares itself. Underwriters will have a 30-day option to purchase from certain selling stockholders up to an additional 1.17 million shares to cover any over-allotments. The company, which has 48.5 million shares outstanding and a public float of 28.7 million shares, did not set a date for the secondary offering.

The company’s initial public offer included 6 million shares offered by the company itself and 6.5 million shares from insiders and other stockholders who had funded the company in its early years.

J.P. Morgan Securities LLC. and Piper Jaffray & Co. are acting as joint book-running managers for the latest offering. William Blair & Co. L.L.C. is acting as co-lead manager, and Stifel Nicolaus Weisel and BMO Capital Markets Corp. are acting as co-managers.

Shares were down $1.35, or 4.9 percent, to $26.32 in midday trading on the New York Stock Exchange.