Flash lighting, can someone tell me where I am going wrong?

[joe_rych]

Ok so I'll give you a quick rundown of my equipment in use for this scenario and what my problem is. It is probably

something simple but this is my first time using monoblocks.

 

Picture this, I have a table set up with items, I have a d300 with a 17-55 (or a 70-200) on a tripod. To my left and right

I have an alien bee 800 flash unit with a umbrella mounted in shoot thru position on an 8ft stands set to about 7 ft.

 

On the camera I have an sb-900 flash unit attached to a quantum sc battery pack (yes it works).

 

The camera was set to take pictures ISO 100 f8 at 125th. The pictures were very dark constantly.

 

 

Here's my problem. When shooting with the alien bees as slaves to the sb900 (light, not radio slave) I was getting

pictures with hard shadows where there should be no shadows do to the location of the alien bees. After taking quite

a few frames I decided to try something else. I unplugged the sb-900 alltogether and tried firing the alien bee's on just

a remote cable from the plug on the camera.

 

This hardwired technique did in fact yeild pictures where I was capturing the light produced by the bees. The pictures

were much brighter and did not have the aformentioned shadows. What difference did removing the flash and going

hardwired make? I cant understand it. That is the only change that took place when the results changed.

 

Thanks for any help the photo.net group can offer!

 

Joe

[mark_sirota1]

You had your SB-900 in a mode that generated pre-flashes, probably TTL or as a Master. The slaves on the AB's reacted to the pre-flash, and fired before the shutter opened.

 

Configure your SB-900 in manual mode to eliminate the pre-flashes.

[picturesque]

i-TTL uses pre flashes to determine exposure. If you were using the SB900 in i-TTL and optical slaves on the Bees, the pre flash sets off the Bees prematurely, which is why the images were underexposed and the shadows were in the 'wrong' place.

[joe_rych]

Nadine, Mark. You guys (and gals respectfully) are right on cue. The flash was in fact in the "on"position in the cookie cutter TTL or what have you mode. That is a new flash as well, so it's a little bit of a learning curve. The flash manual is as thick as the camera manual. yeesh. In any case I am looking forward to throwing the sb-900 into manual and trying out my luck that way. If you guyd are right (and I'd put money on it) then this should work right away; putting an end to using that nasty, clumbsy flash sync cable.

 

Those pre-flashes must be really fast, imperceptable even. It all looks one one flash to me.

 

Thanks for the help, I'm going to go try that out.

[bob_osullivan]

Joe:

 

Just in case that doesn't work, it could also be the umbrella's blocking the light to the alien bees slave sensors. With the setup you describe the shoot through umbrella is between the optical sensor on the bees and the SB900s signal light.

 

As much as I love my bees, they are notorious for having rather insensitive optical slaves. You might have to reverse the umbrellas to bounce mode so the ABs can see the triggering light.

 

When making a setup, keep this in mind and remember that the optical sensor is located on the back control panel of the alien bees and WL lights.

[joe_rych]

Bob, I appriciate the insight on that. I was however able to confirm that the lights were firing as prescribed by the sb-900 via the tracking modeling light that goes out when it is recharging. Last night I switched the sb-900 to manual and set it all the way down and used it to fire the 2 slave alien bees. It works just as they said it would.

 

Thanks!