What is happening when you are changing power

[Jamesino]

What exactly is being changed in the flash when you are changing the power output levels?

Does a 1/1 output use a more powerful burst of electricity and hence, a brighter flash of light than a 1/4 output? Or does the 1/1 flash just have a longer duration than the 1/4 output?

If the latter, will the more powerful flash output have more motion blur?

[PacAce]

The following link should answer your question:

http://www.chem.helsinki.fi/~toomas/photo/flash-discharge/regular.html

Re the motion blur, yes, you'll get more motion blur at 1/1 power than at any other power level.

[tagvestibule]

Setting a higher flash output increases the duration of the flash, not the actual power. It does, however, use more electricity because it sustains the flash longer (thus, the slower recycle times).

As for additional motion blur, I don't know the answer - but I'd be interested to know that as well.

Edit: I type too slow - PacAce answered question 2...

[baekgaard]

What exactly is being changed in the flash when you are changing the power output levels?

Does a 1/1 output use a more powerful burst of electricity and hence, a brighter flash of light than a 1/4 output? Or does the 1/1 flash just have a longer duration than the 1/4 output?

If the latter, will the more powerful flash output have more motion blur?

It depends... Most hand-held/battery-powered flashes charges a capacitor to the same level "always" and just cuts the pulse short if smaller power levels are needed. That's why they have their longest pulse at full power.

Many studio flashes, on the other hand, only charges the capacitor to the level asked for, and then dumps all of the energy into the flash tube when triggered. This way lower flash levels often end up being longer as well.


-- Per.

[PacAce]

It depends... Most hand-held/battery-powered flashes charges a capacitor to the same level "always" and just cuts the pulse short if smaller power levels are needed. That's why they have their longest pulse at full power.

Many studio flashes, on the other hand, only charges the capacitor to the level asked for, and then dumps all of the energy into the flash tube when triggered. This way lower flash levels often end up being longer as well.


-- Per.

Very good point! For some reason, I just assumed that the OP was referring to hotshoe flashes but I see now that that may not necessarily have been the case. :|