Slaving a studio strobe?

[Scott]

Hi, all -

Came into some lighting gear today (thanks, Will!).  Old, old studio lights, on rolling cast iron bases.  The neighborhood lights dim when these things are switched on.  Anyway, they can be slaved using little vacuum tubes.  I tested it out with my 20D - the flash on the Canon triggers the studio flash, but I think there's enough of a lag that the studio light isn't doing much.  I test with and without the strobe, and get essentially the same picture, while I'd expect the strobed shot to be way over exposed.

What'm missing?  Flash novice, but I'd like to figure out how to use these things for portraits of the kids.  In 8x10.  Of course.

Thanks,
Scott

[Kin Lau]

The flash on your 20D is ETTL, and emits a "pre-flash" -  used to calculate the required flash exposure, which is what's triggering the strobes too early. The _real_ flash and exposure comes a micro-second later, but by then, the strobes have already fired.

If you have a manual external flash, or you can switch your EX series flash to manual mode, that will work too.

The other option is to get a "digital flash-slave" or you could even use a PC-cord. The 20D is good to 250W's at PC sync port.

[Major Black]

The 20D is good to 250W's at PC sync port.

Not sure I follow that. ? Do you mean that the onboard flash on the 20D is 250 WS? Used my 20D to trigger over 8000WS.

I'd either do a PC cord or an infra red flash trigger.

[Kin Lau]

Not sure I follow that. ? Do you mean that the onboard flash on the 20D is 250 WS? Used my 20D to trigger over 8000WS.

I'd either do a PC cord or an infra red flash trigger.

Sorry.. typo. That's 250V as in volts. The 10D and earlier are only rated for 6V for either hotshoe or PC sync.

[jake]

Can't you also just stick a little low power flash in the hot shoe on the camera? Something like an old Pentax AF16. If you don't want direct flash from the camera, while playing with lights, I've put the flash in a cold shoe that has a PC cable and mounted it in the camera's shoe backwards & plugged in the PC. The backwards light triggers the slaves just fine. Just don't blast yourself in the eye.

[Scott]

Ok, that got it.  Now, with a lil' Sunpak PC'd into the 20D, I get a completely white image.  Nicely overexposed.  I crank the shutter speed down to 1/1000, and I get a half image of plain white.  This is gonna take some work...

[Scott]

Ok, manual mode, 1/30 at f/22:

Strobe only:


Strobe and Sunpak:


And the strobe in question:


Think this is going to be useful, if I can figure out how to trigger this thing with the 8x10...

Scott

[Kin Lau]

Ok, that got it.  Now, with a lil' Sunpak PC'd into the 20D, I get a completely white image.  Nicely overexposed.  I crank the shutter speed down to 1/1000, and I get a half image of plain white.  This is gonna take some work...

Max shutter speed on the 20D with studio strobes is 1/250.

You have the option of ND's on the lens, or on the flash (harder - and you have to watch that you don't burn it), hooking up an umbrella, or just moving it further away. You could just point it straight up into the white ceiling too.

As for the 8x10, it should work just fine if you have a PC sync on the shutter. The shutters on my Speed Graphics do.

[wfournier]

hey Scott,

glad that they seem to be working . As far as getting it to sync with your 8X10, I believe one of them had a cable hooked up to a co-ax type connection. I believe from the research I did, that is the sync cable. You should be able to come up with some kind of adapter to connect that to the sync on your packard. I don't know if your other shutter has a sync on it or not. Yet another option is to rig up some kind of manual switch to trigger it. Basically open the shutter hit the button and then close the shutter. Shooting at f22 indoors should give you a negligible amount of exposure from the ambient light.