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Mike79
20th of April 2009 (Mon), 02:14
I just did some power tests for my various flashes in manual mode (flash + light meter (sekonic 308s) on tripod) and I got a reading of f11.3 at FULL power. then I reset the light meter, set the flash to 1/2 power and got a reading of f11. I then went to 1/4 power and the flash meter went to f5.6....

Any ideas?
Thanks,

Michael
Angel_LCD
20th of April 2009 (Mon), 02:37
Did you "empty" the flash between the power adjustments?

If you go from 1/1 to 1/2 power without pressing the test button there will be excess power left in the capacitor. Hence almost the same output.
Mike79
20th of April 2009 (Mon), 04:21
I did multiple pops at every setting. I have another 550ex which is working spot on. Might give Canon service centre a call tomorrow.
bobbyz
20th of April 2009 (Mon), 08:50
Did you "empty" the flash between the power adjustments?

If you go from 1/1 to 1/2 power without pressing the test button there will be excess power left in the capacitor. Hence almost the same output.


When using my 550ex in manual mode, I never had to do this.

I know some strobes need to manually dump the excess charge when you go lower on output power.
PacAce
20th of April 2009 (Mon), 12:28
Did you "empty" the flash between the power adjustments?

If you go from 1/1 to 1/2 power without pressing the test button there will be excess power left in the capacitor. Hence almost the same output.

The 550EX is a hotshoe flash. It doesn't work like regular studio strobes so there's no need to "empty" the capacitor of any excess charge when going to a lower power. The only thing you'll be emptying (gradually, that is) by doing that is the charge left in the batteries. ;)
PacAce
20th of April 2009 (Mon), 12:30
I just did some power tests for my various flashes in manual mode (flash + light meter (sekonic 308s) on tripod) and I got a reading of f11.3 at FULL power. then I reset the light meter, set the flash to 1/2 power and got a reading of f11. I then went to 1/4 power and the flash meter went to f5.6....

Any ideas?
Thanks,

Michael

Did you have the dome in or out on the meter? Also, were you standing in the exact same position for each reading (assuming you were metering the light by hand)?