William Robb wrote: > ----- Original Message ----- > From: "Scott Loveless" > Subject: Flash bulbs (or, blast from the past) > > > >> Lately, I've had an opportunity to look at some Kodachrome exposed with >> M2B blue flash bulbs. The character of the light is certainly different >> than that of electronic flash. A couple dozen of these could be in my >> very near future. >> >> And now, of course, my dilemma. I'm hoping that a few of you have some >> experience with flash bulbs and can shed some, er, light on the >> situation. The chart here http://www.flashbulbs.com/bluebulb.htm >> suggests that these bulbs will X sync to 1/30. The manuals for the MX >> and SP500 recommend 1/15 at the fastest, while the K1000 manual >> recommends 1/30. This seems a bit odd to me. As this sort of >> photography is relatively expensive, I'd rather not experiment too >> much. (Kodachrome + processing + bulbs at $1per that may not fire) >> >> Does anyone recall how they may have used these bulbs? I'm guessing >> that I'd be safe at 1/15, but if I can squeeze out 1/30 I'd be happy. >> >> Thanks a bunch, folks! >> > > Bob Shell will know more about this (he has probably forgotten a thousand > times what I know) but I'll try. > Unlike an electronic flash, a bulb flash is not instantaneous light. The > bulb has a warm-up time of several milliseconds prior to it reaching full > output. Some cameras have an X/M switch, X being for gas discharge flash > units, M being for flash bulbs. > The M setting triggers the flash well in advance of the shutter being fully > open to allow the bulb to peak before the shutter opens fully. > In the absence of a camera adjustment, the flash will be triggered when the > leading curtain fully opens. If the shutter speed is set too fast, the > trailing curtain will close before the bulb heats up fully, resulting in > (partial frame) underexposure and poor colour balance. > Some bulbs heat up faster than others, and allow a faster shutter speed off > the X setting. > This may not be accounted for in the camera owners manual, hence the > difference in recommendations from the bulb manufacturer and camera > documentation. > For myself, I would follow the bulb manufacturers recommendation regarding > shutter speed, though you won't go wrong slowing things down a stop either, > providing ambient light levels will allow it. > > William Robb > > > Thanks, Bill. I was actually surprised that I could use X sync at all. My C220 lenses have X and M settings. I had always assumed that the FP jack on the SLRs was the same as M. Loading a short roll of tri-x and burning 3 or 4 bulbs ought to tell me what I can get away with. Thanks again. Much appreciated.
-- Scott Loveless http://www.twosixteen.com/fivetoedsloth/ -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
