This can be problematic because I would have to lower the shutter speed to give me enough time to fire the remote. I'd have to make the flashes stop the motion.
Knowing this, I underexposed my camera by 2 stops. On full power, my flash gives me 3 stops up or down. Since the external flash would fire at full power, underexposing compensated. I underexposed by lowering the ISO to 100 and closing the aperture to the max, f8. My shutter speed started at .3 seconds and moved to .4 seconds. I was able to see the camera flash fire and also fire the external flash manually. Not ideal; but, it worked...sometimes.
For the moment, Pocket Wizards are bit outside my budget. I could always buy a cheap-o flash for these experiments; but, I made the mistake of buying cheap remotes. Well, maybe I'm too harsh. Without the sync cable port on my camera, it's not the remote's fault. A little improvisation gets me in the ballpark.
For example, absent the ability to control my external flash's power, it's a Speedlite 270EX II, I can adjust the power by having my son move back or forward. I could also adjust the power to the on-camera flash. Then, there's the reflector, etc...
I did this mostly to see if I could do it. Otherwise, I'd have chosen a better subject than a work glove on my barbecue grill. It was fun. My kids had fun too.
|First attemp. On-camera flash only. Did not sync the external flash.|
|We got the external flash to fire; but, my son was standing too close.|
|My son stood back a little further. Both flashes captured. Side flash still a bit strong.|
|Misfire. Between shots, the external flash would time out.|
|Placed flash behind and below the glove for a highlight.|
|Moved the camera back a bit. On camera flash power is lower.|
|Turned up the power on the on-camera flash to full. Back flash timed out.|
|Back flash failed to fire again.|
|Camera flash on full, rear flash on full. You can see the glove's shadow on the backdrop.|
|Lowered the power of on camera flash by 1 stop. Got the highlight.|