Multi Flash vs Rear Sync Flash

[BBTM]

Based on the 5600 flash unit.

1) From my own view, this two are different, right?

2) Base on the manual, multi flash flashes at the given speed and times while rear sync flash only does it during the when the shuttle open and before close.

3) Multi flash, from my experience, gives a more balance lighting on the object while sync flash gives a blur movement.

4) Both flash need a dark black ground and a high aperture, right?

5) Will multi flash drain the battery life faster than rear sync flash?

6) Btw, the speed, in Hz, mean what? Like different between 5hz and 15hz, given 5 times each, how is the effect like? Anyone try before?

7) So, which one you prefer? I like multi flash more as you could hear the flash running while sync flash, only 2 flashes. I did an experiment, like the effect.

[Flare]

Hmmm... totally different thing ley...

Quote: 1) From my own view, this two are different, right?

Yes, totally for different purpose.

Quote: 2) Base on the manual, multi flash flashes at the given speed and times while rear sync flash only does it during the when the shuttle open and before close.

Multi flash fires the flash at a present rate and for a preset time so that one can capture a few stages of a certain motion in a single frame with blur trials between the stages.

Rear-sync flash fires the flash near the end of the exposure instead of the begining. This is used to capture one stage of a motion with trials leading to it. it's effect is more obvious in a realtively slow shutter speed with subject movement.

An example will be a falling ball. Same slow shutter speed, if you use normal fill-flash mode, you'll get a sharp clear ball at the top with trials leading down, which makes the ball seems like flying up instead of dropping down:
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not very natural.

With rear sync, the falling ball will first leave a trail, and when the flash fires near the end, the ball is exposed. it'll give a more natural trial leading to the clear sharp ball:
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Quote: 3) Multi flash, from my experience, gives a more balance lighting on the object while sync flash gives a blur movement.

Er... Both are intend to give blur motion, with the multi flash meaning to capture a few stages...

Quote: 4) Both flash need a dark black ground and a high aperture, right?

Not necessary. You just need a situation where you can use a slow shutter speed, or even shutter speed of a few seconds without over exposing the shot in the first place. You may need a smaller aperture to achieve this slow shutter speed, but a smaller aperture would also mean a shorter effective flash range...

Quote: 5) Will multi flash drain the battery life faster than rear sync flash?

Hard to say... But well, you use them for different purpose...

Quote: 6) Btw, the speed, in Hz, mean what? Like different between 5hz and 15hz, given 5 times each, how is the effect like? Anyone try before?

Hz = cycles per second. 5 Hz means the flash will fire 5 times in a second, while 15Hz means 15 flashes a second. Depending on speed of the subject and effect you wanna achieve, you'll use different rates. Just as an example, you got this dancer jumping, and you use a 1 second shutter, and assuming the jump lasts 1 second. when you set to 3 hz, you will get an image with 3 'dancers' and trials in between, while a 5 hz one will give you 5 'dancers' and trials in between. Well, provided you got flash power right in the first place (remeber, it's manual flash).

Quote: 7) So, which one you prefer? I like multi flash more as you could hear the flash running while sync flash, only 2 flashes. I did an experiment, like the effect.

Depends on what effect you want ley... but for multi flash, it's like a form of 'special effects' to potray motion of the subject.

Meanwhile, rear sync-flash is more like an option to achieve more natural/correct looking motion trials over normal 'front synce' fill flash.