Comments on: syncing at higher than max sync speed ..

By: Antonio

Antonio — Fri, 03 Jul 2009 02:09:42 +0000

Ooopsss. Sorry, after reading a bit more and notice that I need to change my Vivitars. But looking at the prices it also seems i need to work more. I guess I will keep shooting and change to at least two SB900’s.

Thanks Neil

By: Tim Wong

Tim Wong — Tue, 30 Jun 2009 16:34:22 +0000

Neil
i just test it out with canon 40d and t5d-r, i tried it with pc port direct connection or trigger by pocket wizard plus II. i got no luck to get pass 1/500 with full power of my quantum. maybe the freewire is the trick?

By: Desmond

Desmond — Sun, 28 Jun 2009 08:24:24 +0000

Hi Neil , that all sounds pretty logical .
On a side note according to my calculations high fp mode on a SB800 drops the power to around 27% [ 2.7m as opposed to 1.4 m ] .
My D40 with its 1/500th synch speed and electronic shutter allows me to get the same distance throughout the range at 4m working distance with an SB24 . http://realsynch.blogspot.com/ .
At F4 1/3200th sec iso 200 it catches most of 1/4 power from my SB24 giving me the same working distance as an SB800 at normal synch speed – except for the fact that the 1/500th synch speed gives me 2.5 times the effective power as well -compared to 1/200th synch speed . This gives me close to 8X the power of an SB800 at 1/3200th sec [ 1.4m as opposed to 4m ] – in practice it is around 2.7 stops more power .
Of course that’s nothing to do with your tests and a focal plane shutter but high -fp mode is a continuous light that gives the same distance with equivalent aperture and shutter speed changes – maybe if they used a smaller flash bulb it would be a slower release for the same power output which would be useful for ‘trick modes’ as in your experiments . I suppose if there was a way to do it better they would have done it by now :) … perhaps if they made more electronically switched shutters it would be better for flash in sunlight .

By: Neil

Neil — Sat, 27 Jun 2009 18:36:30 +0000

David, I was hoping you'd reply. :) From your comment in the max it out post, it looked like you had some knowledge of this. I triggered the Q-flash with the Quantum FreeWire wireless system (FW9T, FW7Q, D22wR) ... so that could very well have influenced the specific timing here, even if inadvertently. Neil vN

By: Dave Graham

Dave Graham — Sat, 27 Jun 2009 00:51:17 +0000

Neil,

How are you triggering the Quantum specifically?

The trouble with this technique on most cameras is usually that the pc port doesn’t fire until the first curtain is fully open, which is too late, because the second curtain is already partly closed. The new pocket wizards get around this by sensing pre-flash communication, and allow you to adjust the timing. Another way is to set an on-camera flash to High Speed Sync, so that it will start firing before the first curtain opens, and use it to optically trigger the big flash.

These t.1 times vary widely by manufacturer, and many (most?) usually advertise their t.5 times (to be more impressive).

The typical speedlight fully charges the capacitor, and regulates power by cutting short the flash, so low power means very short flash pulse, useful for freezing hummingbirds etc.

The typical studio strobe does the opposite – for 1/4 power, it charges the capacitor to 1/4 . The lower voltage on the capacitor means that current takes longer to get flowing, so lower power means somewhat longer flash pulse – maybe not as pronouced an effect.

At least this is my limited understanding.

David Graham