In 1998, just after arriving in Singapore, I wrote a play. I never tried to produce it so it's been sitting on my hard drive waiting for me to get back to it. Finally, it's seeing the glare of the CRT again. I've decided to take a shot at turning it into a screenplay.
Stage plays and screenplays are entirely different. Characters do a lot of talking in a play. Actors have to describe events that take place offstage. The audience at a distance can't read their subtle expressions so they even talk to themselves from time to time. But in film, you can get close. The actors show their emotions instead of telling them.
Another difference is locations. My play takes place on one set. In the film version Annie and Fran eat lunch in a restaurant, instead of Annie's apartment. Annie and Rob will argue have their argument in a car. Sean flashes back to an embarrassing moment in his childhood. Fran delivers flowers for a living, now you'll get to see her do it.
It's quite an interesting exercise to adapt from one form to another. One downside is that the budget increases with every change I make!
One of my favourite films is Hal Hartley's Simple Men, a dialogue driven film in which everyone is trying to understand someone else but no-one manages to make themselves understood. A recent Australian film employs a similar sensibility - its name escapes me - but the director has done a lot of stage work and the film is in a sense a workshop on film, which loses plot coherency but finds the human sides of its actors. Good luck with the adaptation :)
About a dozen years ago I set to work on a screenplay. After about 15 pages I gave it to my roommate for his opinion, and he said, "This could work, but it's not a movie. It's an opera."