Re: flash duration

[ADavidhazy <andpph@xxxxxxx>]

Herschel,

I'd use a white object against a black background but the approach is  
valid I think. It is often overlooked that camera shutters make good  
improvised chronometers. If using a dropping object synchronization of  
object with a location in space may be a challenge especially if rate  
is fast. Also make sure shutter is traveling perpendicular to subject  
motion to not introduce focal plane shutter vs moving image distortion  
artifacts re: blur length determination.

An oscilloscope and photocell is a good approach as well (and probably  
the most "professional") but I assumed we were talking about kludged  
solutions! ;)

On the turntable ... if you can photograph a CD turning at 7200 rpm  
then a blur measuring 43 degrees will stand for a 1/1000 second  
exposure time. Measure arc of blur in degrees (use protractor?) and  
divide by 43,000 degrees per second to get approximate exposure time.  
Good point about unbalancing the CD ... if taping a white paper strip  
go across diameter. May want to allow for the size of the mark in arc  
blur determination. Subtract it from blur to find out more accurately  
how much the mark moved during the exposure. FP shutter artifacts may  
introduce some error but you want approximations anyway I presume.

Andy