ADvice on my first "flashed" session..

Ok, here is my equipment: 40d + couple of lenses 70-200 L IS , 18-55, 50mm 1.8, 430EX II, two white umbrellas, two stands for those, mounts for flashed and wireless triggering device and also another 580ex I can borrow, and a backdrop with stand etc..

What I am shooting: lots of models, singers etc. all girls, they will come for an audition and at the end of their auditions we will take their pictures for reference and future use etc with their permissions..

The points I need advice on:

- If I understood the flash theory correctly you use shutter speed to control the exposure of the background (if the background is far away of course..I am not sure if this applies to a model who is in front of a backdrop..) and use aperture to control the exposure of the areas that flash lits. Is this right? So where do I get my exposure from? the model? and then add the flash + umbrella combination(s) as fill light? how do I meter if I want to use the flash as main light? If there is adequate light already light in the room can I still use the flash as main light? What is the correct procedure? If you ask me what type of effect I would like to get out of the pictures I would say young, energetic type of vibe, so probably high-key or between medium and high key..

Thanks so much in advance.

Emre

It sounds like for this setup, lights + background, you will want the flashes to provide all the light for the exposure. Short of having a light meter here is something you can do. Start with a shutter of about 1/125 and an aperture of about f/5.6 or f/8 and an ISO of around 400. Set your lights up where you want them and then one by one start dialing them in. Turn on the main light and put a subject in place. Try and get something white in the shot like a white towel and put it on their shoulder. Take a shot with just the main light. Evaluate. Look at it on camera. Look at the histogram. You should get data on the histogram right up to the right edge with that white towel in there. But the in the image you should be able to zoom in on the white towel and still see detail. If not then adjust the aperture or ISO or light distance, or a combo of any of these. Next, start turning on the other lights, fill, hair, background, etc. and get them dialed in and you're ready to go.

Get a flash meter.

emre2006 wrote in post #6294228
you use shutter speed to control the exposure of the background (if the background is far away of course..I am not sure if this applies to a model who is in front of a backdrop..)

If the background is lit by ambient, then yes.

emre2006 wrote in post #6294228
and use aperture to control the exposure of the areas that flash lits. Is this right?

Depends.
If the flash is on manual, the exposur is determined by ISO, aperture nd flash output.
If you use an ETTL wireless setup, the preflash is metered, and flash output (thus exposure) set by the camera...

emre2006 wrote in post #6294228
So where do I get my exposure from? the model? and then add the flash + umbrella combination(s) as fill light?

Not sure what you are saying here...

emre2006 wrote in post #6294228
how do I meter if I want to use the flash as main light? If there is adequate light already light in the room can I still use the flash as main light?

As long as the ambient get's overpowered enough by flash, flash is main light.
Ambient can be controlled by ISO, aperture and shutterspeed.
So by varying the shutterspeed you only affect ambient, so can set a ratio.

emre2006 wrote in post #6294228
What is the correct procedure? If you ask me what type of effect I would like to get out of the pictures I would say young, energetic type of vibe, so probably high-key or between medium and high key..

High key is low contrast, bright images, often against a white background.
Not easy to do well in an uncontrolled environment without experience IMO.

If you can, go to the location and do a test before the actual event.
At the very least have everything setup well in advance at the event.