I was afraid to give away my age and mention the infamous "quench" tube. ;-) Had one explode once, it was very cool, that is, after I changed my shorts!
Several of my flash owners manuals list the flash duration range. The 285HV for example lists 1/1000 to 1/30,000 in auto and 1/1000 in manual mode. By shooting the flash directly into the sensor I have stopped some very fast action, such as the cliche' "hammer smashing egg". Perhaps rather than trying to measure the duration one should refer to the specs, or simply contact the manufacturer and ask. Don > -----Original Message----- > From: Graywolf [mailto:[EMAIL PROTECTED] > Sent: Sunday, December 12, 2004 10:42 AM > To: [EMAIL PROTECTED] > Subject: Re: flash duration > > > This thread seems to have even more misinformation than usual in > it. I tried > looking up Dr Harold Edgerton's (the inventer) diffinitive book > on Electronic > Flash on the web, but the only thing that seems to be in print is > a book of his > photographs. > > Anyway the duration of an electronic flash is simply a result of the R/C > (resistance/capacitance) time function of the flash tube and > capacitor bank. And > is easily calculated from the formulas available in any basic electronics > reference. Small strobes usually have rather short durations, and > large powerful > one have longer durations. Most older studio and 200+w/s portables have > durations of 1/200 of a second or so. Dinky things like my > Vivitar 252 have a > duration of maybe 1/2000 of a second or less. > > There are various ways of limiting the output and thus the > duration of a flash. > The most comon nowadays is the thyrister circuit which cuts the > power after the > desired light level is obtained without fully discharging the > capacitors. One of > the older circuits cut the main flash tube out of the circuit > while the rest of > the energy was discharged trough another (hidden) flash tube. > > Anyway the original poster (I have lost track of who that was) > will probably > find useful information if he does a search on "stroboscope > photography" which > is the term usually used for the very short flash durations he is > asking about. > > > graywolf > http://www.graywolfphoto.com > "Idiot Proof" <==> "Expert Proof" > ----------------------------------- >
