this is the first time I've used stiduo flashes, as I've been practicing with tungsten.

The problem is the shot below:
http://i29.photobucket.com/albums/c270/paulwhittle/bad-pic.jpg

i had a flash to my left with large softbox, fired by radio trigger.
i had a flash on the right, triggered by it's photo cell. Canon 350D, Manual, 1/400 2.8 ISO 100
Most shots were fine, but some came out like this. I can't understand the dark area.
I wondered if it's something to do with flash synch, but don't really know much about that.
any ideas?

I would say your shutter speeds too fast.

Try setting of around 1/125 f8 iso100 and move your flashes until it looks about right at these settings.

Well thats what works for me :thumb:

It's possible that the flashes are re-cycling at different speeds and in this case the one on the right didn't fire ?

When I used my old 300d with studio lights the spped had to be 1/200 or less, anything faster resulted in some odd images...

The shutter speed is way to fast, as Andy (69wrx) has already stated, 125th sec, F8, ISO 100.
Try using a hand held lightmeter, and adjust the lighting so that you have F8 on the subject, then shoot at the above settings. Pics should come out fine then. Just rember to play around with light positions, to get the desired effect, but to always check the light everytime you move them with the meter:)

Paul:)

cheers guys

tried again with slower shutter speeds
My light box is huge - around 4', and my studio's only 3m wide, so I'm a bit short of room for manoever now!

http://i29.photobucket.com/albums/c270/paulwhittle/Sarah-wedd-dress.jpg

I'm not that interested in traditional shots, but it's a good way to learn the ropes I think - I can get more adventurous once I can reliable shoot as I want

With flash (and no other light source involved) shutter speed has no effect on exposure so long as the shutter speed is at the camera's x-sync speed or longer, ie 1/200sec on a Canon 350D. In the first pic, it is quite clear that the right hand side of the image is receiving ambient-light-only exposure, and no flash.

It's a focal plane shutter thing. There's a chapter on it in the Understanding Photography sticky at the top of the page ;) Edited to add link on focal plane shutters http://bbs.scoobynet.com/6159608-post12.html

Richard.

PS For the shot above, a big soft box and maybe a reflector on the other side is really all you need. If you want to stick with a dark background, use the second light hidden behind the model pointing at the camera - it will give a nice feminine outline highlight and lift her hair tremendously from the darkness. Or just use a lighter-coloured background. Pinkish perhaps?

Agree with what Richard has said, but TBH I'm far from an expert in studio setup.

One thing which I can't quite put my finger on is that is in the first pic the highlights obviously indicate that the main light source is off to the photographers left, but there is a very prominant shadow also on the left which seems to indicate a light source from the right.

I'd suggest that both flash fired, but due to the way the flashes are set, they aren't working together to provide a correct exposure and even lighting. Was the one to the right set to provide an ETTL exposure but failed due to no connection to the camera ?

Richard or Paul would be better informed than myself to provide advice - but I have had problems along this line.

At least you've sorted the lighting to provide even lighting for the second shot.

Gareth

thanks for the replies.
yes there was a softbox on my left, and a flash to the right. the shadow confused me too. Being a conservatory, there's quite a bit of ambient light, but I guess as the camera's metered for using flash, it still appears very dark.

I'm not sure about ETTL - I was using a radio trigger on the left, and the right was triggered by it's photocell (I have a second radio trigger, but can't find a common frequency)
I wouldn't normally use black, it's just the only thing I have which would show a white dress well. I mainly use seemless white, but need to invest in other colours really.