Omni at 60 deg up, why?


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kitty2

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Apr 21, 2005
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#1
Hi CSer,
I was adviced that need to set my external speed lite flash angle up to 60 deg with omni when taking long exposure (2sec). It is to brighten my object face before camera taking background (I am using prosumer nikon CP 8700 and nikon SB28-dx).
I was wondering why must be tilted up ? can't just fire at 90 deg with omni?
Any purposes or diffrent in picture? :dunno:


BTW, I heard about curtain so what is 2nd curtain compare to 1st curtain?

Pls help me to clear my doubt and share your experience.

Thank you in advace
 

chanxj

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Sep 4, 2006
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#2
The omni bounce is tilted 60 deg up due to the diffusing property of it and so that lighting will be more even. Go experiment with the different angles to get a feel.

The front curtain mode is when the flash fires when the shutter opens, while the rear curtain mode makes the flash fire only when the shutter is about to close.

In rear curtain mode, sometimes it is used in a scenario where if you try to freeze the action using the flash in front curtain mode, you tend to have funny output. For example a person is holding a candle and walking towards you. The flash freezes your action, but as you move the candle flame moves and you have you standing there holding the candle and have a stream of light in front of you while in real life the stream of light should be behind you.



So in rear curtain mode, it allows the candle light to move first, then at the end then exposing you and thus the light is from back to front and not front to back.

Front Curtain
Start: End
Flash Fires <-Exposing of candle flame->
Movements: You>----------------------------Flame

Rear Curtain
Start: End
<-Exposing of candle flame-------->Flash Fires
Movements: Flame---------------------->You
 

kitty2

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Apr 21, 2005
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#3
Thanks dear...

but if I tilted 60 deg up then I won't be able to control my flash likewise normal position
90 deg than how?

Which curtain should I choose if my object just stand and don't move at all (above scenario)?
 

catchlights

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#4
the purpose of omni bounce is to bounce the light into omni direction, when it tilted in 60°, meant most of the light is throw forward, and some of the lights are bounce on the ceiling, walls and hit on your subject, so this how the softness of lights come from.

are you referring 90° as in the flash tube aim at your subject? if it is this way, the omni bounce is only serve as a diffuser, does not change the size of the light source, so does not have much soft effect.

anyway, omni bounce is design to work in indoor, so using it outdoor is not effective.

for your 2nd question, the names are call front curtain sync and rear curtain sync, the default flash sync mode is front curtain sync. not sure your camera do have rear curtain sync mode.
 

kitty2

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Apr 21, 2005
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#5
ya..ya.. make sense! so I learned from your sharing idea.

I do appreciate for your opinion bro...
Thanks
 

chanxj

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#7
Thanks dear...

but if I tilted 60 deg up then I won't be able to control my flash likewise normal position
90 deg than how?

Which curtain should I choose if my object just stand and don't move at all (above scenario)?
I would use front curtain flash. Cause for rear curtain flash if your hands are not steady to take in the natural lighting properly, there could be blur. Its all personal preference. Try it out yourself thats the best way.
 

catchlights

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#8
I would use front curtain flash. Cause for rear curtain flash if your hands are not steady to take in the natural lighting properly, there could be blur. Its all personal preference. Try it out yourself thats the best way.
it doesn't make sense.
if the shuttle speed is too slow, and the hands are not steady, the shot will have hand shake issue regardless front or rear curtain sync.

the only issue of rear curtain sync is sometime can't be very certain about the flash will fire at the right time, especially people moved after hearing the shutter fired, and the flash caught them at off guard.
 

chanxj

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#9
Its just that in rear curtain flash the metering meters more for ambient light.(ok technically not, but just dunno how to explain. Its just that the flash is more a fill in.)
 

catchlights

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#10
unless the flash is set at TTL BL mode, the flash is be act as a fill light.
in A or P mode, when camera set at rear curtain sync, it will become slow sync also.

You statement is correct, I have not been using this two exposure modes, so have to take out the camera to confirm this.
 

lsyapw

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Dec 27, 2007
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#11
the purpose of omni bounce is to bounce the light into omni direction, when it tilted in 60°, meant most of the light is throw forward, and some of the lights are bounce on the ceiling, walls and hit on your subject, so this how the softness of lights come from.

are you referring 90° as in the flash tube aim at your subject? if it is this way, the omni bounce is only serve as a diffuser, does not change the size of the light source, so does not have much soft effect.

anyway, omni bounce is design to work in indoor, so using it outdoor is not effective.

for your 2nd question, the names are call front curtain sync and rear curtain sync, the default flash sync mode is front curtain sync. not sure your camera do have rear curtain sync mode.
Hi, how should the omni be tilted when taking portrait?
I get shadow on one side when taking portrait using the omni.

Thanks in advance.
 

catchlights

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#12
Hi, how should the omni be tilted when taking portrait?
I get shadow on one side when taking portrait using the omni.

Thanks in advance.
when rotate the camera for vertical shot, you aim the flash tube towards your subject, but tilt your flash tube slightly upwards about 45~60° (as in camera still in vertical position). you still will have shadow cast on one side, but most of the lights are direct upward and forward instead of sideway.

hope this help.
 

lsyapw

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Dec 27, 2007
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#13
Thanks catchlights.
Guess there is no way to get rid of the shadow when using the omni bounce in vertical position.
 

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