People who use pinhole cameras often seem cooler than other people, and they are. To make one, pretty much all you need to do is finish your box of oatmeal. Instead of a glass lens you use a small hole. Your shutter is a flap. Da Vinci is your inspiration (“O what a point is so marvelous!” he said about the hole). To celebrate WorldWide Pinhole Photography Day, RayKo is offering pinhole workshops, as well as an opening reception for pinhole photographers Kath Kreisher and Rebecca Rome and winners from the “Juried Pinhole Photography Exhibition.” And starting at noon, a rolling, multiple-aperture camera obscura, otherwise known as a bus, is pulling up to the photo center and giving people free rides. You sit in it and watch a 360-degree, animated projection of the world passing on the windows, which are blacked out and covered with little holes — pinholes — as you listen to the work of sound artists Colleen Burke and Walter Sipser, who make music for every city the bus camera visits.