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| p.1 #13 · How to prevent ghosting with slow shutter speeds?? |
I'm responding mostly to add my voice to the "rear-curtain does not prevent ghosting" choir. However, it's not as simple as "rear-curtain doesn't do that."
First, understand that all rear-curtain does is fire the flash immediately before the shutter closes, as opposed to normal flash that fires immediately after the shutter opens. The problem you're having is not with flash timing. The problem is with the shutter speed being too long.
There are two common uses for rear-curtain flash. The first is to make those cool images of cars where you have bright streaks from the lights, and then a nice sharp image of the car. Rear curtain is used to make sure the streaks are behind the car. With normal flash sync, the streaks end up in front of the car...which usually doesn't look good.
The second use of rear-curtain sync is to capture backgrounds. A typical example is of a riverside cityscape shot. Let's say you have a person standing by a river at night, and there's a nice cityscape across the river. You need two separate exposure for the shot...you need a flash exposure for your subject, and an ambient exposure for the cityscape. This is where rear-curtain sync works best. The shutter will open for an extended amount of time to capture the dim cityscape. Meanwhile, your subject is in the dark and standing still, waiting for the flash. Right before the shutter closes, the flash fires, illuminating your subject. You've now properly exposed both your subject and your background.
In the situation I described above, rear-curtain is used and no ghosting occurs. However, that's only because the subject was too dark to cause any ghosting. When both your subject and the background are being illuminated by the same light, the successful use of rear-curtain flash is dubious. Even when people are standing still, they're not standing still. No one can hold perfectly still for even half a second. In fact, your images show camera blur...even YOU can't hold steady at the shutter speeds you where using!
To start solving your problem, you first need to really learn about lighting. I suggest the book Light Science and Magic.
To address your specific problem you simply need to increase the shutter speed to suppress ambient light. Set your shutter speed to 1/120s, and allow your lighting to provide all the light for your scene. If you want the background illuminated, then get another light and put it on the background. Another possible solution is to illuminate the scene by bouncing light from the ceiling. But no matter what...you need to increase the shutter speed. In this situation, ambient light is your enemy and you need to get rid of it.