High Speed sync with Off Camera speedlight

[bob williams]

Just curious, can you set high speed sync with off camera speedlight?


I am shooting with a 7D and a 580 EXII. I was going to try high speed sync off camera using the on board IR for communication, But......This option is greyed out on the camera when the flash isn't attached, it also deosn't seem to be available on the flash either.


Both camera and flash are set to manual.


Am I missing something or is this just the way it is? both manuals are useless here.


Thanks,


Bob

[Shea Design]

Find the external speedlight control (typically the 3rd utility tab) in your menu, and you should find options for HSS 1st or 2nd curtain. In theory as I do not have much time with the 7D and have never used it with a flash.


-Shea

[bob williams]

Just curious, can you set high speed sync with off camera speedlight?


I am shooting with a 7D and a 580 EXII. I was going to try high speed sync off camera using the on board IR for communication, But......This option is greyed out on the camera when the flash isn't attached, it also deosn't seem to be available on the flash either.


Both camera and flash are set to manual.


Am I missing something or is this just the way it is? both manuals are useless here.


Thanks,


Bob
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[neuroanatomist]

C'mon, Bob. Just find the external speedlight control (typically the 3rd utility tab) in your menu, and you should find options for HSS 1st or 2nd curtain.


[:P]


Sorry, couldn't help it. UnlikeShea, I did read your post (twice, in fact). HSS only works with the Speedlite in the hotshoe mount. It doesn't work via wireless, and it doesn't work via a PC sync cable.


--John

[Shea Design]

I read it twice, but with my bad eye. My good eye was making oatmeal. Congratulations you're still the top forum nerd. -S

[neuroanatomist]

In theory as I do not have much time with the 7D and have never used it with a flash.

Then why answer Bob's question?

I read it twice, but with my bad eye. My good eye was making oatmeal. Congratulations you're still the top forum nerd. -S

I read it twice because Bob seemed to feel the need to repost his question after you 'answered'. But, I think you made the right decision on where to focus your attention, or else you might have burned your oatmeal. Sorry if I offended, Shea. If actually posting a correct and helpful response makes me a nerd, consider me nerd-ified. [8-|]

[peety3]

It doesn't work via wireless, and it doesn't work via a PC sync cable.

High-speed sync doesn't work with wireless flash? I think that's news to me. Can't confirm it without getting off the couch though.


For the sake of elaboration, it doesn't work with a PC sync cable, as the sync cable just carries a signal of "fire NOW!". At speeds faster than normal sync, the shutter curtains are always in the way at least a bit, so the shot isn't properly illuminated. HSS has the advantage of a message from the camera "fire for X milliseconds at Y power level" along with a message "start now, the shutter is about to open". That's why the new PocketWizards have to be brand-specific, to have the data feed instead of the basic "fire NOW!" signal.

[neuroanatomist]

That's why the new PocketWizards have to be brand-specific, to have the data feed instead of the basic "fire NOW!" signal.

Actually, I can't speak for PWs or other RF triggers. But, for the purpose Bob intended - HSS via IR from the 7D's on-board flash - it won't work. It seems that's not true of all IR triggering, since apparently the ST-E2 can trigger HSS.

[Sheiky]

This one is very helpful.


Some quotes:


"5. I thought the flash control uses IR, why do I see the flash?



The built-in flash is not capable of only emitting IR light - unlike Canon's ST-E2 flash controller, which uses IR LED's to communicate with the external flashes. The built-in flash emits the full spectrum of light which includes IR light that is received by the slave flashes. The ST-E2 pulses light in the same manner, you just can't see it."


I think that could be the reason why the ST-E2 can use HSS and the in-camera flash can't.


Jan

[peety3]

The built-in flash is not capable of only emitting IR light - unlike Canon's ST-E2 flash controller, which uses IR LED's to communicate with the external flashes. The built-in flash emits the full spectrum of light which includes IR light that is received by the slave flashes. The ST-E2 pulses light in the same manner, you just can't see it."


That explains why the ST-E2 can use HSS and the in-camera flash can't.

I'm sorry, but this quote does not explain why the ST-E2 can use HSS and the in-camera flash can't. HSS isn't dependent on wavelength.


HSS involves pulsing the flash at (reportedly) 50khz. Wireless remote flash using Canon's optically-triggered system involves a Canon-proprietary signal encoding method that can be emitted by HSS-like pulses from a master flash. If the 7D onboard flash can do HSS, and if the 7D onboard flash can signal wireless remote flash (which uses HSS-like encoded pulses), it would seem to me that the 7D should be able to do HSS with remote flashes.


For non-HSS wireless remote, the signal would essentially be "Channel 1, normal flash 25ms after sync signal, group A at 1/1, group B at 1/32, group C at 1/4, &lt;timing bits&gt;, &lt;sync signal&gt;". For HSS wireless remote, the signal would essentially be "Channel 1, HSS flash 11ms after sync signal for 3.78ms, group A at HSS1/1, group B at HSS1/32, group C at HSS1/4, &lt;timing bits&gt;, &lt;sync signal&gt;". Perhaps that HSS wireless code word is too power-hungry for the on-camera flash circuit to handle while reserving enough power for the on-camera flash to provide a full-power HSS pop if it's to contribute to the shot.