Jens, it's a SLOT, not a SLUT. You're getting Cotty exited. ;-) Don
> -----Original Message----- > From: Jens Bladt [mailto:[EMAIL PROTECTED] > Sent: Saturday, December 11, 2004 6:27 PM > To: [EMAIL PROTECTED] > Subject: RE: flash duration > > > Jostien. > The discribed metod is very similar to the one I came up with. I > just don't > believe that 60 rounds pr. second (= 3600 RPM) is enough to measure flash > durations as short as 1/50.000 sec. At 3600 RPM/60 RPS the disc will only > turn app. 2,5 degress in 1/10.000 of a sec. and 0,5 degrees at 1/50.000 > sec., which is probably not really enough to measure properly. > > Tomorrow I'll try out the other method I described, firering a flash > directly into the camera at perhaps 1/6000 secs. > I will post my experiences. > Perhaps someone can figure out how slim or wide the slut in the > focal plane > shutter of the *ist D is at different speeds? > > Jens Bladt > mailto:[EMAIL PROTECTED] > http://hjem.get2net.dk/bladt > > > -----Oprindelig meddelelse----- > Fra: Jostein [mailto:[EMAIL PROTECTED] > Sendt: 12. december 2004 00:40 > Til: [EMAIL PROTECTED] > Emne: Re: flash duration > > > Kevin, Jens; > > Maybe this is worth reading? > http://www.hiviz.com/activities/guidebook/hsptutor.pdf > > It contains a passage on how to test flash duration. > > Jostein > > ----- Original Message ----- > From: "Jens Bladt" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Sunday, December 12, 2004 12:09 AM > Subject: RE: flash duration > > > > I'm not sure if I made some errors (below). > > Anyway, to measure (in degrees) the a flash duration of perhaps > > 1/50.000 > > second, you'll need a very fast moving object. At a speed of 1118 > > miles/hour > > just 1 cm would last 1/50.000 of a second. > > > > > > Jens Bladt > > mailto:[EMAIL PROTECTED] > > http://hjem.get2net.dk/bladt > > > > > > -----Oprindelig meddelelse----- > > Fra: Jens Bladt [mailto:[EMAIL PROTECTED] > > Sendt: 11. december 2004 17:08 > > Til: [EMAIL PROTECTED] > > Emne: RE: flash duration > > > > > > I believe a coammonly used technique is to photograf a moving object > > (with a > > known speed) , moving past some kind of scale. Perhaps a > > recordplayer-plate. > > It runs perhaps 78 rounds pr. minute. If one round is 360 degerees, > > it will > > run 45x360/60 = 468 degrees in one second. In 1/1000 sec. it's 0.468 > > degrees. So, it seems a record player it not fast enough. You may > > want to > > find a faster running electronic engine and perhaps a much larger > > plate/disc > > to mount on it. > > > > I guess you could mount a disc on a fast running engine - perhaps an > > electric power drill (you deed to know the speed, and perhaps you'll > > need a > > gear to raise the speed). Cut a slot in the disc and mount some > > photopaper > > behind the disc. Shoot the flash through the slot in a way that the > > light > > will go through the slot no matter how far it has reached, while the > > engine > > is running, hitting the photopaper, which should NOT rotate. Do the > > shooting > > in a darkroom and make sure only the falsh light can hit the > > photopaper. > > Then develop the paper. Measure the balck part and find out how many > > degrees > > it covers. Some easy calculataions based on the speed of the disc > > will give > > you the wanted result. > > > > > > > > If the disc runs 3000 RPM this equal 3000/60 = 50 rounds in one > > second > > (RPS) > > 50 rounds = 50 x 360 = 18000 degrees. 18000 degrees in one second = > > 18 > > degrees in 1/1000 sec. > > Or 1.8 degrees in 1/10.000 sec. > > > > So you may want a faster engine, perhaps 12000 RPM, which will give > > you 7.2 > > degrees in 1/10.000 second > > 24000 RPM will give you 14.4 degrees in 1/10.000 second > > 48000 RPM will give you 28.8 degrees in 1/10.000 second > > > > So, I guess if you use a disc with a large size, you can measure the > > flash > > duratione with a slower electric engine. > > > > > > > > > > Jens Bladt > > mailto:[EMAIL PROTECTED] > > http://hjem.get2net.dk/bladt > > > > > > -----Oprindelig meddelelse----- > > Fra: Kevin Waterson [mailto:[EMAIL PROTECTED] > > Sendt: 11. december 2004 13:33 > > Til: [EMAIL PROTECTED] > > Emne: flash duration > > > > > > Is it possible to measure the duration of a flash? > > Possibly in micorseconds or something? > > > > Kind regards > > Kevin > > > > -- > > "Democracy is two wolves and a lamb voting on what to have for > > lunch. > > Liberty is a well-armed lamb contesting the vote." > > > > > > > > > > > > >
