Need some Lighting Advice

[julie32]

I shot an event for fun over the weekend, outside at night under a tent with crazy glowing lights...about 100 people dancing.

I did get some really good shots, but I struggled a bit with it. Here's what I had trouble with.
I wanted a fast shutter speed to freeze dance action. This wasn't working for me, the shots were just too dark, and I was open to 2.8. (using a 24-70L on a Canon 5D). When I used the flash (580EX) the shots look like they were taken during the day and the cool glowing effect of the blue, purple and orange laser lights were gone.
I therefore used a slower shutterspeed 1/40, 1/60 and the shots are too soft for my liking.
I do believe this is all due to my inadequate knowledge of my flash capabilities. I was using ETTL, but I really need to understand how the flash works in conjunction with my camera. I don't understand dialing up or down with the flash and how that differs from going up or down a knotch with the exposure settings etc...

Any help, explanations or reading materials will be entirely helpful. I'm eager to get better, but I need some guidance.

Thank you so much, in advance.

Julie

 

[henryp]

Flash exposure is set by the aperture. When you lost the lighting effects it's because your flash exposure was good but your shutter speed was too fast for the ambient light. When you slowed your shutter, your exposure became a mix of flash & ambient. This is often a great effect, but the slower shutter speed requires some attention on your part. The flash burst should freeze motion like dancers, but (depending on the amount of ambient light and your shutter speed, the amount of blur can range from a little to a substantial amount. There's no magic rule since each situation is different,

 

[Big Mike]

That's right. It's a delicate balancing game between flash exposure an ambient exposure...because both will be recorded at the same time.

In this situation, I always shoot with flash in E-TTL and camera in manual mode. I will play with the FEC to control the amount of exposure from the flash. I can then play with the aperture and shutter speed to control the ambient exposure. The flash (in E-TTL) will give you enough light for the aperture you choose (up to it's power limit) and the shutter speed does not affect the flash exposure (just keep it at or below the max sync speed (probably 1/250 on the 5D).

Also, you can adjust the ISO. Turning it up will increase the ambient exposure and increase the flash range...but give you more noise. As long as your exposures are accurate, I wouldn't hesitate to use ISO 800 or 1600 in that situation.

 

[julie32]

Mike,

I understand everything you said and it makes sense to me. But I don't understand much about FEC. Is there a way you can explain it to me without it being too much trouble for you?