I'm totaly green to studio lighting and spent much of yesterday trying to get it to work, but couldn't. I'm using a D70 with red eye flash (two flashes) to trigger the Studio flash heads but my pics are still coming out dark.
Most strobes with built in optical triggers will not work if there is a preflash (they fire on the preflash instead of the main flash, before the shutter is open).
Even if you turn off redeye reduction, your D70 will still generate a preflash (about 20ms before the main flash).
One way around it is to change your Flash Mode to Manual with a fixed power output set ((full, 1/2, 1/4, 1/8, 1/16). Manual Flash won't use a preflash.
Wein also makes some digital slave triggers designed to ignore a preflash (for example, the Wein Digital Peanut Slave Triggers).