Did you know that if you have a modern sophisticated flash like a Canon 580 EX, you can set it to strobe/repeated flash mode (“Multi”)?
This makes the flash fire a number of subsequent pulses, at a certain frequency, at a certain power level.
To activate this mode on a 580EX, Press the MODE button until MULTI appears; then set power level, number of pulses, and frequency in pulses per second.
Which then gives you pictures like this, of my hand dropping a slice of dried banana:
And another version:
Those were taken with the flash set to fire 10 pulses at 50 Hz, each at 1/32nd of full power. The camera was in manual mode.
(You do not even have to meter: look at the back: the flash indicates how far away the subject should be with your chosen flash/aperture and ISO settings!)
Challenge to physics students out there: use this image to estimate the acceleration of gravity, in meters per second squared. Or, if you already know that it is 9.81 meters per second squared, use this to work out the size of the banana)?
This (the flash part, not the physics part!) is among the many subjects I teach at my Advanced workshops, like the David Honl special on Saturday in Toronto., for which I believe there are just a couple of spots left.