I've been without a flash in the couple months I've had my K100D, mainly because I haven't yet found the extra $300 in my budget, but also because I don't know the first thing about flashes and haven't started reading up (because it's a moot point if you can't afford one anyways). The point is, while digging through one of my closets I found an old camera bag with an Olympus OM10 film SLR and a Vivitar Auto Thyristor 3700 flash. It was DOA due to a set of exploded AA's in the battery bay, but after a few minutes of touch-ups with a soldering iron I heard that oh-so-beautiful sound of capacitors charging, and soon I was flashing away. The flash is probably 25 years old, but it seems to be in working order. My problem is that I don't know anything about flashes, and one thing I didn't find was the users manual. By randomly messing with switches and slides I found out "thingy makes a bright light when I push the shutter if I set it to M/TTL", but beyond that I'm at a loss. Can anyone clue me into what these switches do? What are DIN and ASA and what does the FSTOPS/FEET indicator tell me? What are the modes on the bottom slide beside "M/TTL"?