iTTL and Blinking

MIKEROPHONICS

MIKEROPHONICS

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Mike
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I recently had to shoot a "run and gun" event red carpet arrivals and used OCF in iTTL. I usually use full manual, so it became really spirants how many people were blinking because of the pre-flash.

Is this normal and is there any way around this?
 
Not 100% sure about this, not actually tested it as such, but I'm pretty sure you'll get less delay between the pre-flash and final flash if you use a TTL cord as it cuts out all the instruction transmissions that go on between master and slave in remote working. The flash basically operates as if it was on the camera with virtually instant hard-wired commands.
 
It was the first time I have used iTTL. Always worked in full manual before, but was shooting red carpet arrivals with rapidly changing flash to subject ratios, so I had no choice.
I was using YN 622TX and sB700 with Yn622 and a Lastolite McNally Ezybox.

As I usually shoot full manual I was shocked at the difference. It was very apparent.

If anyone can back up HoppyUK's theory I would be intrigued to know.

I was surprised how ok iTTL was actually. Nice to try something new
 
The wireless TTL is *very* fast... I've never noticed a difference in delay using a cable but I've not done any kind of strict testing. I suppose different RF triggers could be slower/faster...
Using rear curtain sync w/ TTL can add a significant delay and make your problem much more significant, as can red eye reduction.

But yeah, some subjects will react very quickly and there's nothing to be done but switching to manual (tough for run/gun).
If you have the flash power/battery you might be able to shoot 2-3 frames in CL and catch them after the initial blink (I can do this w/ the AD360 and Y-cabled battery pack at shorter distances). And of course, brighter conditions with less flash minimize the reaction/reflex.
 
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I just tested it, and while there may be something in the theory, in practise there is no significant time difference between pre-flash and main flash delay, when fired using a hard-wired remote flash cable, and wireless. I don't have a radio TTL trigger to hand, so the test was done using optical wireless mastering. I doubt there would be any difference with radio.

For interest, I can also say with a fair degree of accuracy that the delay between the pre-flash and main flash is pretty close to 1/15sec. That's with a Canon 5D2 that has a fairly sluggish shutter, with 580EX flash. It may vary by camera and by brand. Just thinking about how this all works, the electronics side of things happens very swiftly and it's probably the mechanical delays (mirror rising, shutter opening fully) that accounts for the delay.

Edit: I believe that the average person's reaction time is about 1/20sec. I know mine is close to that, which is enough time for someone to have their eyes at least half closed if they react to the pre-flash.
 
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It's probably worth noting that there is an "intermediate fix" for the pre-flash issue; use the flash in A (auto) or AA (auto aperture) mode. In these modes the flash itself meters the scene w/o pre-flash in order to determine it's power setting. Basically, variable flash based on scene luminance using a "dumber" system.

I never use these modes so I tend to forget about them... and that might be why I never use them...
 
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sk66 said:
It's probably worth noting that there is an "intermediate fix" for the pre-flash issue; use the flash in A (auto) or AA (auto aperture) mode. In these modes the flash itself meters the scene w/o pre-flash in order to determine it's power setting. Basically, variable flash based on scene luminance using a "dumber" system.

I never use these modes so I tend to forget about them... and that might be why I never use them...
Click to expand...

With Canon, that only works with a gun that has an external sensor, ie 580EX-II or 600EX-RT. But is a good workaround for Nikon guns with external sensors.

But I'm being a bit simple here :) With Canon, the easy way around most pre-flash problems is to press the * star button. That fires the pre-flash and locks the flash exposure, so when the real picture is taken, there is no pre-flash (y) It's also handy if you want to take a flash reading off-centre, say to avoid the exposure being fooled by a white shirt. There must be a similar feature on Nikons?
 
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Wah! I have some more learning to do. Thank you gents, and just as I thought I was getting the hang of this flash malarkey. So I have to check up on AA mode and fv lock - in Nikon equivalents.
 
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