I was given a load of Canon stuff and among it was a remote flash trigger which will set of second flash from first with no wired connection just uses the flash. So tried it with Pentax K10D and the result was darker than using just built in flash. So I tried with Vivitar 3500 and it worked OK. So thought I must have some setting wrong. Tried 1/30sec and 1/180sec still dark. Tried leading and trailing still dark. Tried flash compensation still dark. Using tripod with Vivitar 3500 on camera and second flash below I got some really good pictures of berries in the wood. However it took for ever working out exposure. Set to about 12 inches and altered f stop until right as for example f9 at 1/180 second ISO100 so moved to next with same settings again 12 inches away. This time f22 at 1/180 second ISO 100. Wanted to use for wedding but so unpredictable not really an option. However I can explain why. The sensor which see the light is all well and good in a room but out doors not aimed at subject but scene beyond. Found the only way was to set to motor drive. Manual was too strong. However the built in flash is TTL so works far better. But has a shadow with close up and needs some extra light from below but for some reason it switches it off premature. If I can work out why then maybe I can work out a way around the problem. Of the 6 flash guns I own only the Vivitar 3500 can be used on the hot shoe. The others have around 200v on the contacts. And the Vivitar 3500 is rather powerful and quite a long way from lens. Good for red eye but not close up. Although I have the dedicated base it was for earlier Pentax so only two contacts not three. In auto mode (Green) very unpredictable. I am guessing camera only fires flash when light is too low but not very good for fill in flash. So I seem to end up in manual mode. But being a powerful flash in motor drive mode it runs on about 1/20 of full power so very short duration of about 1/20000 of a second. Very good for freezing motion. And on manual with zoom can still use with 400mm f6.8 lens. But with the three auto metering modes only works indoors outside it's a dead loss. Has anyone else used one of these old flash guns and if so how have they got on?