Hi ya' Rik,
I saved a couple of pre-flash exposures of flies so that you could see how fast the flies react to the e-ttl pre-flash...
When I shot these tests the temperatures were in the high 60s°F. Normally I don't catch a long-legged fly in the frame at all. Cooler temperatures must slow down the fly's reactions.
Picture wing flies can react to the e-ttl pre-flash, too. They are just not as fast as long-legged flies.
The flies aren't reacting quite as fast as I first thought. Here's how e-ttl flash works:
1) When you trip the shutter the flash fires a pre-flash. You can actually see this flash through the viewfinder.
2) The main flash fires when the shutter curtains open to fully expose the cmos sensor to the flash exposure. Typical x-synch for electronic flash.
3) The time lag between the pre-flash and the firing of the main flash exposure is approximately 65 milliseconds.
Long-legged flies can react fast enough to the pre-flash to be able to jump completely out of the frame in 65/1000th of a second Picture wing flies barely have enough time to get their butts of the leaf During our original discussions we forgot to add in the extra time for "shutter lag".
Best regards as always,
For Rik Littlefield...E-TTL Pre-Flash
Moderators: MacroMike, nzmacro, Ken Ramos, twebster, S. Alden
- twebster
- Site Admin
- Posts: 1518
- Joined: Mon Apr 19, 2004 10:55 pm
- Location: Phoenix "Valley of the Sun", Arizona, USA
For Rik Littlefield...E-TTL Pre-Flash
Tom Webster
Administrator
Phoenix "The Valley of the Sun", Arizona, USA
Think about this...maybe Murphy is an optimist!!!
Administrator
Phoenix "The Valley of the Sun", Arizona, USA
Think about this...maybe Murphy is an optimist!!!
-
- Posts: 727
- Joined: Fri May 06, 2005 11:57 pm
- Location: Richland, WA, USA
- Contact:
Tom, super job!
These pictures really nail down that it's the pre-flash spooking the flies, as we did conjecture in our earlier discussions at http://www.photomacrography1.net/forum/ ... hp?p=18070. The metering flash goes off, the fly starts to spook, the mirror goes up, the shutter opens, and (yawn...by some standards...) when the image-forming flash finally goes off, the fly is nowhere to be seen.
To get gone in 65 milliseconds is pretty fast, but definitely not record-breaking. (Too bad -- I always like to see records broken ) Changing the units may make the number seem less impressive -- 65 milliseconds is more than 1/16 of a second!
Anyway, I guess the rule for shooting these flies is pretty simple -- be real sure that pre-flashes are turned off. Easier said than done, I suppose, for many of the new cameras, particularly if all the photographer has is integrated flash.
--Rik
These pictures really nail down that it's the pre-flash spooking the flies, as we did conjecture in our earlier discussions at http://www.photomacrography1.net/forum/ ... hp?p=18070. The metering flash goes off, the fly starts to spook, the mirror goes up, the shutter opens, and (yawn...by some standards...) when the image-forming flash finally goes off, the fly is nowhere to be seen.
To get gone in 65 milliseconds is pretty fast, but definitely not record-breaking. (Too bad -- I always like to see records broken ) Changing the units may make the number seem less impressive -- 65 milliseconds is more than 1/16 of a second!
Anyway, I guess the rule for shooting these flies is pretty simple -- be real sure that pre-flashes are turned off. Easier said than done, I suppose, for many of the new cameras, particularly if all the photographer has is integrated flash.
--Rik