----- Original Message -----
From: "Herschel Mair" <herschel@xxxxxxxxxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students"
<photoforum@xxxxxxxxxxxxxxxxxx>
Sent: Saturday, January 29, 2011 1:00 AM
Subject: Re: flash duration
Thanks guys
Some interesting advice... I really need to buy a turntable! Lots of uses
in product photography, QTVR etc. plus this... Alberto, I'll do the shots
and send you the results to do the math/analysis :-) Actually I've mixed
up your advice and I think what I'll do is shoot a falling black marble
against a white background - continuous light at 1/3 stop intervals from
1/250 up to 1/8000. Then shoot it in the dark with the flash, and compare
results...
The shutter is the most (Only) reliable timing device I have. I suspect
that the useful duration at minimum power is between 1/1000 and 1/4000
Is there fault in my reasoning?.. tell me
shutters, even electronic ones, are notoriously unreliable - well that's
what i found when testing to 1/44 000 th of a second. Admittedly that was
with older film cameras with both electronic and mechanical , but at least I
*could* test those.
Digicams - who knows, I suppose one could bounce a laser off the shutter and
measure the duration of the reflection. My guess is, from the many ways
digital cameras have varied from the stated specs, they're likely not to be
any more accurate with their shutter speeds than any other camera.
Interestingly the old Pentax K1000s I tested (more than 5, can't recall
precisely how many) were the closest to the stated speeds and had the least
deviation from their average. Some cameras like the Canon T90 and the
comparable Nikon of the day showed no variation whatsoever between the
1/2000th setting and the 1/4000th setting. most odd.
Want an oscilloscope? you have one already! A light sensor rigged to a
computers sound card (AD converter) would be the most accurate device I
could think of, and it'd allow you to measure not just the duration but
relative intensity, so you could determine the standard flash duration =)
it would only cost you spare change in parts to cobble this together
a quick, lazy look on the web finds:
http://www.zeitnitz.de/Christian/scope_en
http://www.zelscope.com/
http://www.epanorama.net/links/pc_sound.html
http://www.electronic-engineering.ch/radiocontrol/circuits/osziconn/connect.html
