this is a very beautiful effect. However it cannot be high speed sync at 1/100s. I think what hapened is is the flash created a sort of double exposure and the normal exposure (normal light) captured the other wing position. up to 1/250s the 20d has normal flash sync speed, even if your set your flash to high speed sync.
Love this four-winged bird! ;-) Any idea how you got this exposure? Is this the high-speed flash's continous flashing than gives you this lovely result?
