Blurry subject when shooting with flash

[jaworsk3]

I just started working with a flash (580EX II). I did my first practice shoot yesterday. I had the flash wirelessly triggered by the ST-E2. I chose a huge abandoned building for the shoot because I felt it would give me a lot of interesting uses of the flash. Some rooms were pitch black, otherse had some ambient light seeping through the windows. The hallways were nearly pitch black with small amounts of daylight coming through open doors. The rooms were small and some were painted in very unique colors which allowed me to create interesting effects when bouncing the flash. I used the Lumiquest Promax system with the softbox diffuser cover for some of the shots as well.

What I noticed is that some of the shots were quite blurry. I clearly was wrong, but I expected flash shots to be crystal clear. I'm certain it was something I did wrong, but I just can't pinpoint it. Other shots did come out quite clear. Shutter speeds ranged from 1/15 to 1/200, depending on how much ambient light I wanted in the shot. Apertures also varied from f/1.8 to about f/11. I didn't notice a correlation between aperture, shutterspeed, and the blurriness. Maybe it was the way the light was hitting the subject? I really am left clueless about it. Any help would be greatly appreciated. Thanks.

[troymm]

which lens were you using. Maybe your lens just had trouble focusing in low light.

[DavidW]

When using flash, your image is a combination of an ambient light exposure and a flash exposure. Whilst the flash exposure happens very quickly, the ambient light exposure does not. At 1/15s, you have significant potential for camera shake if you were hand held. That's one way you can get blur in flash shots.

Another possibility is failing to achieve sharp focus - the ST-E2 will provide an AF assist, but you may still not be achieving decent focus with it. You can test this out at home in a darkened room.

Some sample images would help a lot in diagnosing your problem, as would your commentary on the settings you were using.


By the way, my feeling is that the diffuser cover for the Promax System isn't that much use. It costs you a stop of light, and the only use I can think of for it is at macro distances. Beyond that, it does nothing to soften the light; it's just costing you battery life.



David

[Curtis N]

Could be any number of things, or a combination. 1/15 shutter is pretty slow. f/1.8 gives a very narrow DOF. And low-light focus could be an issue.

If the AF assist on the ST-E2 is working though, it should snap to focus on a blank wall in the dark. Your camera has to be in one-shot AF mode for it to work.

[jaworsk3]

The only one where I shot 1/15 was a shot when the subject was sitting in front of a bright window. He was backlit and when the window was properly exposed he was completely black, so the 1/15 caused no problems there. I was also using a tripod in all shots, including those shot at 1/200.

Does the AF assist work automatically when the ST-E2 is attached to the camera or do I have to do something to it?

[DavidW]

Camera shake isn't likely to be the issue, then - especially if you were using a remote, which is always recommended when using a tripod.

The problem may just be mirror slap - some of your shots were in the 'danger zone' for that - the answer there is to use mirror lockup. Lock up the mirror, wait a couple of seconds for all vibrations to die down, then press the shutter button again to fire the shutter and drop the mirror. However, vibrations from mirror slap shouldn't result in pictures that were 'very blurry'.

AF assist should be automatic - did you see the red pattern flash on when focussing?


A sample image (maybe a 100% crop that shows the problem as well - or a link to a full size image) with the settings and your commentary on them would help tremendously. Without that, we can only guess at what went wrong.



David

[jaworsk3]

I deleted most of the blurry pictures, but I'll see if I can recover a few to show you guys. I always use a wired shutter release cable when shooting with a tripod. Mirror shake seems like a possibly cause of the problem. I wasn't keeping an eye on the red light of the ST-E2. It had just come in the day of the shoot and I hadn't had time to read the manual. The photos weren't "very" blurry...just unclear enough to make them unusable. Like I said, some of the shots from that day were very clear and I was very pleased with the results. Could the lack of clarity have been caused by how I set up the lighting?

I have a shoot coming up in about a week. I haven't used mirror lockup yet....is that something I should definitely do for the shoot? Is there a downside to it?

[jaworsk3]

I just read that when shooting with lenses under 100mm, mirror vibrations don't cause too much loss of sharpness. I was shooting mostly at 20mm and 50mm that day. Is it likely that mirror vibrations would have been the cause of the lack of sharpness? Is mirror lockup something I should do during my next shoot?

[macro junkie]

I just read that when shooting with lenses under 100mm, mirror vibrations don't cause too much loss of sharpness. I was shooting mostly at 20mm and 50mm that day. Is it likely that mirror vibrations would have been the cause of the lack of sharpness? Is mirror lockup something I should do during my next shoot?
i shoot up to 1:5:1 life size and never ever use mirror lock up..