I think the photodiode and oscilloscope a really good suggestion. Or a counter-timer and photocell to measure the duration of light. Safer than guns! Chris -----Original Message----- From: owner-photoforum@xxxxxxxxxxxxxxxxxx [mailto:owner-photoforum@xxxxxxxxxxxxxxxxxx] On Behalf Of David Dyer-Bennet Sent: 28 January 2011 16:49 To: List for Photo/Imaging Educators - Professionals - Students Subject: RE: flash duration On Fri, January 28, 2011 05:00, Christopher Strevens wrote: > Flash duration is about 1/10000 sec. I would think a bullet from a gun > that > has just been fired. Use a wire to hold the flash off so it triggers as > the > bullet breaks the wire. The circuit would be a transistor going to ON to > fire the flash and an transistor I the inverting amplifier configuration > holding the flash fire transistor off until the wire is cut. > > The muzzle velocity of you gun should be available from the gun smith and > so > the length of the blur will enable you to compute the duration of the > flash. > > Warning! Guns are dangerous so don't shoot yourself or anyone else during > the measurement. You will need a couple of sandbags to safely stop the > round. Using an air gun is somewhat easier, in that you don't need as heavy a backstop, and the legal complications aren't as messy. With a real gun, the muzzle velocity varies with both the gun itself, AND the ammunition. However, if you know anybody who reload seriously, they probably have a chronograph to measure how their ammunition is performing, so you could use that to get a fairly accurate reading on the bullet velocity, and then in turn use that for measuring your flash duration. At this point, however, it might be easier to find somebody with an oscilloscope instead, hook up a photocell and power source to it, and just expose the photocell to the flash. -- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
