Studio Lighting Newbie...

I got my lights and have been playing around. I've been reading tons and still trying to digest it all. But I did come across something and was hoping someone could help.

I just wanted to see different effects of changing the ISO, aperture and SS. So I set a teddy on a stool and my 5D on my tripod. I put the AB800 ringflash at 3 oclock and the AB800 with a 10 degree grid on it at 10 oclock. When ever I turn the SS above 300 ish I would only get the top half of the picture. The bottom half would be dark. The top half I did get wasn't great quality and probably shouldn't be with the settings but I was wondering why this would happen.

Thanks
Jeni

Your shooting above the maximum speed your camera allows while shooting with flash. Your second curtain is closing so fast, the sensor cannot get the entire image while the flash bursts. The max speed is usally 1/250.

X-sync speed of the 5D is 1/200.

Page 102 of the instruction manual refers to that, and recommends 1/125 or slower for large studio flash units.

Perfect Thank You so much, bbvdm!

Just what I was looking for, the technical explanation.

So essentially I really only have aperture, ISO and the lights to play with? SS is somewhat limited.

I did see that in the manual. As I said I am a newbie to studio lighting. I just wanted to make sure that what I read and was thinking were correct.

Shutter speed won't affect the flash exposure at all.
The usual procedure is to set your ISO at 100, aperture where you want for the DOF you need, then adjust flash power for correct exposure at that aperture.

Thanks CurtisN!

I'm reading your flash bible. Very helpful, thanks so much!