ETTL - FP Sync question


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chenwei

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hi all, recently tried the FP sync and got some questions on this. to my understanding, there are 2 scenarios 'll be using this mode:

1. lighting too bright and need a higher speed than x-sync speed
2. lighting not enuf and still need higher speed than x-sync speed to avoid handshake

for 1 i tried no prob on that, but it doesn't seem like to work in 2, or something wrong in my way to think of this (2)? Recently I tried some macro shots and used manual mode, wif settings of 1/250 shuttle speed and F11, all the shots are totally black or underexposed. wat's wrong?

am i supposed to have the flash on 60 degree, or direct? or 8 degree down? am i not supposed to use ETTL mode?
 

Zerstorer

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Case 2 doesn't hold at all. The lower the ambient light level contributing to exposure, the lower the shutter speed needed to freeze motion.

If ambient light is nil, your effective shutter speed would be that of the flash duration.(Typically 1/1000 or more) regardless of what your actual shutter duration is.

The reason why your shots are all black and underexposed is that your flash doesn't have sufficient power to work in FP-sync mode at f11. FP-Sync mode drastically reduces the effective output of your flash as it fires in high frequency bursts.
 

tomcat

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I shot macros with manual settings more severe than yours using high speed flash synch all the time without any problem. What external flash are you using and did you remember to switch it to HS mode before using?
 

chenwei

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Zerstorer, ambient light is not the concern, so according to what u say, does it mean that I can never go higher than x-sync speed since FP sync reduce the effective power?

tomcat i'm using sigma DG500 super, not sure wat's ur HS mode but i was using ETTL mode with FP function enabled.
 

Zerstorer

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chenwei said:
Zerstorer, ambient light is not the concern, so according to what u say, does it mean that I can never go higher than x-sync speed since FP sync reduce the effective power?
What I'm saying is that if you don't need ambient light or if there is no ambient light, your mechnical shutter speed can be anything and yet you will still be able to freeze motion and do not need FP-sync modes at all.

The more dominant ur flash exposure compared to the ambient light, the lower the shutter speed needed to freeze a shot.
 

chenwei

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Zerstorer said:
What I'm saying is that if you don't need ambient light or if there is no ambient light, your mechnical shutter speed can be anything and yet you will still be able to freeze motion and do not need FP-sync modes at all.

The more dominant ur flash exposure compared to the ambient light, the lower the shutter speed needed to freeze a shot.
zerstorer i got u, but the prob is that, whenever i on my flash, my max shuttle speed on my eos 300v can only go to 1/90, which is not enough for me to avoid the handshake. in order to get to higher shuttle speed, i must force in FP sync mode.

or... is this the limitation on my cam? where u all won't find the prob in higher end?
 

tomcat

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chenwei said:
tomcat i'm using sigma DG500 super, not sure wat's ur HS mode but i was using ETTL mode with FP function enabled.
I'm using the 550EX to take macro shots of fishes in high-speed flash synch mode. The flash must be switched to high-speed synch mode which is also known as FP mode on analogue Canon SLRs. Did you get the 'small lightning bolt' and 'H' symbol on your camera's LCD display which is indicative of forced FP mode?
 

chenwei

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tomcat said:
I'm using the 550EX to take macro shots of fishes in high-speed flash synch mode. The flash must be switched to high-speed synch mode which is also known as FP mode on analogue Canon SLRs. Did you get the 'small lightning bolt' and 'H' symbol on your camera's LCD display which is indicative of forced FP mode?
yar tat's the one i tried, and i got all the things u mentioned. did u put ur flash head 60 degree upward? or just direct to the subject?
 

tomcat

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chenwei said:
yar tat's the one i tried, and i got all the things u mentioned. did u put ur flash head 60 degree upward? or just direct to the subject?
Direct at the subject. The flash would work in any position actually but you would need shoot directly at the subject to maximise the reach of the flash due to the drastic drop in flash power in high speed mode.
 

chenwei

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tomcat said:
Direct at the subject. The flash would work in any position actually but you would need shoot directly at the subject to maximise the reach of the flash due to the drastic drop in flash power in high speed mode.
i think i'll try again next weekend, bad side of using film not digital where can't see wat is the result.. >_<
 

chenwei

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okie i found the answer...

Note an important point - FP mode does not help you freeze motion; the name “high-speed sync” is a bit misleading in this regard. Normal flash photography is very good at freezing motion on film, since a burst of electronic flash is so incredibly brief. When a scene is illuminated primarily by a really brief flash of light then you aren’t going to get much motion blur - it’s almost as if you used an incredibly high shutter speed in the thousandths of a second. However when you use FP mode flash, the flash unit pulses the light output over a longer period of time in order to simulate a longer-duration burst of light. Since the flash burst is no longer particularly brief you can’t freeze motion as easily, even with high shutter speeds. The mode is called high-speed sync since it lets you synchronize flash exposure with high shutter speeds, not that it lets you take high-speed photographs.
 

tomcat

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The use of high-speed flash synch does freeze motion in practice and I found it to be very useful in taking aquarium pics. If I do not use high speed flash sync, I would not be able to use shutter speed faster than the X-sync speed of the camera (which in my case is 1/200s). With high speed synch, I can use shutter speeds of 1/400s or faster and apertures of f/8 - f/11 routinely to freeze the motion of fishes in my aquarium shots and attain adequate depth of field at the same time and at the correct exposure.
 

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