The three principal owners of First Foto Inc. plan to make an offer to buy out the company's 300 public stockholders for $3.35 per share and convert the firm into a private company.

Organized in Alexandria First Foto takes pictures of newborn babies before they leave the maternity ward. A few months ago the company moved its offices to St. Charles, Mo., a St. Louis suburb, but most of its stockholders live in the Washington area.

The buy out proposal, announced yesterday, was made by First Foto's three officers, R. W. Harmon, A. M. Schrier and Sheldon R. Lending. The three now own 71 percent of First Foto's shares, which are traded over-the-counter.

"We're going nowhere as a public company," said Lending, vice president of First Foto. Since the company sold stock to the public in 1971 its shares have never sold for more than $1.50 each, and are now quoted at about $1, Lending said.

The $3.35 price offered for the public share is based on an independent appraisal of the stock's value, he added.

Lending said First Foto apparently will be the first company to "go private" under recently revised Securities and Exchange Commission regulations governing the buying out of public stockholders.

The formal notice of the offer will be mailed to stockholders next month and a shareholders' meeting to vote on the offer is tentatively planned for Nov. 14.

Harmon, Schrier and Lending own enough stock to assure that their offer will get the two-thirds vote required for approval. Lending said the company has voluntarily agreed that the buy-out will not be approved if it is opposed by holders of more than one-third of the shares not owned by the three officers.

The offer to be made to shareholders is technically a reverse stock split under which one share of a new stock will be issued for every 13,040 present shares. Only the three officers now own enough stock to get one full share after the reverse split. Owners of fractional shares will be required to sell their stock back to the company at the offering price.