My new Alien Bee B800 is causing blur

Well I finally got a decent studio light and it's causing me problems. My specialty is catching kids in action in my studio. We do a lot of jumping and dancing. I've always been able to get clear pictures of them jumping until I started using my new Alien Bee B800. Now I have significant blur. Here's an example:

I've been thinking a lot (and stressing a lot) about it and I'm starting to think that since the flash duration of all my other lights, including my fill light, is 1/1000th sec and the flash duration of my B800, which is my main light, is 1/3200th sec, then I'm getting different images in my 1/200th shutter speed. Do you think this is the problem or could it be something else like slave tripping speeds? My whole studio is wireless even from my camera to my lights.

Any help would be greatly appreciated - I'm losing sleep over this!
Thanks,
Amy

Camera settings? For that matter, which camera? What's its rated X-sync speed with an external non-EX flash?

Oh yes, of course. I have a Canon EOS Digital Rebel and am told I can't go any faster than 1/200th shutter speed. So shutter speed was 1/200th. Aperture was F9.0. ISO 100. RAW capture mode. B800 was set between 1/2 and 1/4 which supposed slows down the flash duration some.

Thanks,
Amy

Do you still get the problem if the modelling lamps are turned off

Terry

I don't use the modelling lamps. I only use the strobes.

ISTR some studio strobes recommending a slower X sync setting. I know my 20D manual recommends 1/125 with studio flash, even though it's rated at 1/250 with the EX flash series. As you're in the studio, and can control your lighting, why not try 1/60 or 1/125?

I was thinking that my shutter speed shouldn't be a problem because the studio lights are so much faster than my shutter speed. I'd like to stick with the higher shutter speed because I'm capturing kids in action. However, it's worth a try.

I've been reading about "ghosting" where different images are caught because of dramatically different flash durations. But I'm not sure if my lights are considered dramatically different.

Time to do some more noodling in the studio!

Thanks Jon!
Amy

intresting thread... Let me know how it does, I was also looking to buy some AB 800s

Are you using a light meter? Or a Guess and Go meathod?

Also, check the alien bees website, its got some data about shutter speeds and stuff like that.

To me the blur looks like a focus issue, not a motion thing. However, to be sure that a slow flash duration isn't the culprit, I would suggest trying an experiment with ONLY the AB flash unit(s) in play. See if there is any difference.

As another experiment, try cranking the flash units up and stop down the lens a bit more for a better depth of field.

You say you are "wireless". What kind of setup are you using? Optical slaves, radio, or what?

For us to help more, a full-resolution crop of the image(s) would be useful.

I've posted another image to the web, this one is high resolution.
http://www.KidsBeingKi​dsPortraits.com …/action_blur_hi​gh_res.jpg

I do a lot of these type of pictures and yes I do get some out of focus shots because kids do move around a lot. But I usually get many good in-focus clear shots but with the B800 I'm not getting any clear shots. They all have this funny blur to them.

I'll try some shots without fill or background lighting to see if I can get something clear.

My wireless setup is triggered by this doohickey that I bought on EBay where the transmitter is on the hot shoe and the transceiver is plugged into one of my lights. So my camera triggers one of the lights by radio and then the rest of my lights are slave lights.

As far as my flash meter is concerned, I bought a nice one but it just doesn't seem to ever get the right exposure so I always have to experiment with different exposures to get one that works.

Thanks for the input!
Amy

The duration of an AB800 on full power is 1/3200th of a second, that should be enough to stop just about an motion. How much ambient light is around? The only thing I can think of is that the ambient light is too strong and is causing ghosting around the sharp image the studio light makes.

What flash meter do you have? My Sekonic L358's pretty much spot on.

Amy, in the high-res photo you posted I see the very same thing I did in the first. What's blurry is the hand that's in a very different plane from the body. Her skirt edges are fairly sharp as is her left hand. Her right hand is much closer to the camera. I suspect rather strongly that the blur is mostly out of focus and maybe a tiny bit of motion. It's depth of field that needs to be increased to resolve the problem if I'm correct. Stronger light or a higher ISO (or a combination) setting would allow you to stop the lens down a notch or three and improve the depth of field.

Tim could be on to something too, if you have relatively strong ambient light. By upping the power of the flash and adjusting the camera accordingly, you could minimize the effect of ambient light.

Well you wise folks are likely on to something. It turns out that I was at a longer focal length than normal and my depth of field was reduced because of that. I will also increase my light power so I can push my aperature even smaller. And now that I think about it, I even had an extra ambient light on that I usually don't have on. I don't think that should make a difference but I suppose it's possible.

My crappy flash meter is a Polaris flash meter that I bought brand new. It is never right. I should have returned it but at the time I just assumed that no flash meter would ever work correctly .

Thanks everyone and I'll let you know once I get my DOF way up, whether I'm still seeing any "ghosting" or not.

Amy

Ok, I played around tonight in my studio and I was able to get action shots without the blur so it's not a problem with flash durations! Unfortunately I can't increase my subject light power because I'm limited by my backlight abilities while I'm using a white seamless backdrop. Some day I'll have a whole studio of decent lights, but one thing at a time for me.

Thanks again!
Amy