achew, there are many ways to reduce the effect of the on-body flash signal.
1) use a shutter speed that is faster than the flash sync speed of your body, thus triggering HSS (1/200s would be sure for the A200/A300/A350)
2) use a piece of overexposed, developed film negative over your pop-up flash
3) use a darker aperture e.g. F11
4) use a lower ISO e.g. ISO100
The moment you enter HSS mode, the signal is totally not captured by the camera. Of course, the downside is the fast shutter speed, which will reduce ambient light... but you can do 1/200s F1.4 ISO1600 to bring up the ambient light.
On the other hand, you can make daylight appear to be night, using 1/800s F11 ISO100...
If you can find a strip of exposed negative (usually the black end of a film) you won't need to do any of the steps above.
yo boss..thanks for the tips ya.....seems like its slightly more troublesome than i thought..haha....previously i thought this could b easily done with some setting on the camera/flash..lol..btw..does other brand's flash also need to do the same thing???
i think no1 is probably more suitable for me..lol..since i wanna try to shoot at dark enviroment..and jsut wanted my flash to send light from a certain direction =)