James Franco -- I'm Really Making a Porn Documentary

If you thought James Franco was kidding this month when he said on "Conan" he was directing a porn documentary ... think again -- because TMZ spies caught a glimpse of Franco earlier this summer ... staking out one of the biggest porn studios in the country.

Franco was seen chatting up some of the, umm... employees at Kink.com. James is helming a project about the company which plunked down $14.5 million to move into the old San Francisco Armory in 2006.