Paul C. Buff, Inc. Technical Forum

It does look counter to what i said, but it is much the same way first curtain and second curtain sync work. At the beginning of the of the flash pop, most of your energy is expended very rapidly causing a sharp image, and your flash is at the most intense, so your most saturated lear portions will be here. As the flash "fizzles out", its intensity does as well, so your exposure from flash will become less and less, until the flash is gone. simply put it is a sudden start, but a gradual stop.