HELP! dark pictures when slave triggered

i have been practicing using on camera flash plus off camera fill with strobes.

here is my gear - 5d + 430 EX (not II) , slave is an interfit 300 watt strobe.

when i shoot with only on camera flash the pictures expose correctly, but when i shoot with the slave the pictures are dramatically darker.

i have read that ETTL can cause this due to the "pre" flash. is there a work around? does using radio triggers alleviate the problem? right now i am only using the slaves optical sensor.

EDIT: also.. i am shooting in manual mode, does shooting in aperture priority help with constantly changing light sources like at a wedding reception? i plan on using this setup at an upcoming event. on camera flash on the 5d + strobe angled toward the dance floor, should using aperture priority and ettl help compensate for changing light sources? ultimately i know shooting manually is optimal but i am not there yet where i can nail every shot every time.

Have you try using exposure comp?

i haven't, but i do not think that has to do with it. there should be more light available if anything the image should look blown out. i will post a picture shortly

Pictures would definitely help.

here are 2 pictures shot with the same settings, the darker one was actually shot with the on camera AND the slave yet somehow is darker. please excuse the mundane and rather terrible content

Set your 430ex in manual mode. This eliminates the preflash and then your strobe will fire in sync.

this fixed it! however now i have to work on light ratios, thanks

I use radio triggers to solve that problem. Much eaiser and cheaper in the end.

I just noticed the mention of using this setup at an event. You do realize that if you use the optical slave on your strobe, it is going to fire with the flash of every point and shoot at the event. Other than getting a work out, it might not be ready when you need it. Get some inexpensive wireless triggers.

dedsen wrote in post #14536887
You do realize that if you use the optical slave on your strobe, it is going to fire with the flash of every point and shoot at the event.

disco party!

yes i planned on purchasing triggers by then. do you guys have some trusted brands you can suggest? cactus, radio poppers, others?

oceanbeast wrote in post #14537055
yes i planned on purchasing triggers by then. do you guys have some trusted brands you can suggest? cactus, radio poppers, others?

I have the Phottix Stratos (original version) and love them. It lets me trigger off-camera manual flashes and keep a speedlight on camera with TTL pass through for either AF assist or fill flash. Plus they work with the new Odin transmitter if you want to eventually upgrade to TTL radio triggers at some point.