Macro the 1/f rule and flash duration

Started Sep 8, 2008 | Discussions thread
OP fred vachss Senior Member • Posts: 1,292
Re: I did the same sorts of experiments.

Thank you very much for showing these results.

I agree that they do show faster response for the 580EX and MT24 than I appear to get with the MR14. In particular, it appears that the fastest response (of 350us) that I got from the MR-14 is similar to what you got at between 14 and 1/8 power on the MT-24.

Perhaps this is the result of my using ETTL and exposure to control duration rather than explicitly varying flash power and perhaps it is the true behavior and flashes like the MR14 with lower guide numbers don't allow for as much modulation of duration as the high GN flashes like the 580EX - and indeed you get shorter minimum durtation out of the 580 than the MT24.

That said, I don't think it's a problem in my instrumentation. I used the same photodiode and scope that I routinely use to characterize laser pulses down in the 10 ns regime. While it's not optimized for visible light and doubtless produces more noise than a properly optimized detector would I'm pretty certain that detector/circuit response time is not at issue.

Regardless, it looks like I should explicitly vary the flash head powers and repeat to remove this ambiguity.

Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow