Anyone can explain theory of Omnibounce?

[espn]

Hi nutek,

Can you help me by explaining why "you could be wasting a lot of battery juice if the flash has to fire more power unnecessarily each time?"

I don't undestand why the flash will consume more power with the OB on.

Thanks.

When you shoot with the omnibounce, the flash needs to pump out more power to maintain the same amount of output, thus your battery drains considerably faster with the omnibounce.

Your working distance is also shortened when you use the omnibounce.

 

[nutek]

When you shoot with the omnibounce, the flash needs to pump out more power to maintain the same amount of output, thus your battery drains considerably faster with the omnibounce.

Your working distance is also shortened when you use the omnibounce.

Exactly as espn said. Thanks!

 

[Isaiahfortythirtyone]

but the flash doenst auto detect OB right? does that mean then that you have to exposure compensate? if so, how much usualy do you compensate for?

 

[Isaiahfortythirtyone]

oh, and using the OB, does that mean that wide angle flash is covered? >18mm?

 

[willyfoo]

but the flash doenst auto detect OB right? does that mean then that you have to exposure compensate? if so, how much usualy do you compensate for?

The flash does not detect the OB.. assuming you use TTL, the camera will need to pump more power out to achieve the same amount of light as without the OB.. this is done automatically thru TTL. Thus you do drain your batteries and is pointless using it when the ceiling too high or is dark.

I keep seeing guys use the omni-bounce in a disco/pub environment and I'll just inform them that they are better using a modified bounce card or just shooting straight on.

 

[Canew]

When you shoot with the omnibounce, the flash needs to pump out more power to maintain the same amount of output, thus your battery drains considerably faster with the omnibounce.

Your working distance is also shortened when you use the omnibounce.

espn,

So, correct me if I am wrong. With the OB on, the flash will continue firing (in terms of mili-seconds) till the correct exposure is achieved, hence, more battery power is used up. Is that correct?

 

[nutek]

wrong. flash duration is usually around 1/10,000 or faster. It won't match your camera shutter speed. Try setting your camera shutter speed to 10s and see if your flash stays on for 10s.

Flash power dependent on voltage and current (P=IV).

More flash power needed => more current needed.

Current = Q/t (charge over time)

=> More charge needed per unit time.

=> More electrons being sucked out from the battery per unit time.

=> Less juice in your batteries for your remaining shots.

 

[Zerstorer]

wrong. flash duration is usually around 1/10,000 or faster.

Not really. It can vary between 1/800-1/20000 or less depending on power output. Flash output is controlled by the duration of its burst.

 

[nutek]

ok i stand corrected, thanks!

 

[Canew]

Flash output is controlled by the duration of its burst.

Eerrrr. OK. What I meant was if there is a OB present, the duration of the flash will be longer (vary between 1/800-1/20000 - quoted by Zerstorer) to achieve the correct flash exposure of the shot, hence more power is consumed?

Thanks for putting up with my question.

 

[Zerstorer]

Eerrrr. OK. What I meant was if there is a OB present, the duration of the flash will be longer (vary between 1/800-1/20000 - quoted by Zerstorer) to achieve the correct flash exposure of the shot, hence more power is consumed?

Yes. As the part of the light is lost and redirected by the omnibounce, the intensity falling on the subject is less and hence the flash burst will be allowed a greater duration to make up for the lightloss.

 

[Canew]

Thanks for the clarification, Zerstorer.