2 SB900's versus a QFlash for output power

Joined
Dec 26, 2009
Messages
1,266
Location
Philadelphia
Anyone have any idea what the power differences would be for one QFlash versus 2 SB900's? I'm only concerned about the power output at full manual. not asking about recycle time, overheating, HHS, or anything.... Any thoughts or experience?
Thanks,
Jon
 
Joined
Apr 3, 2006
Messages
5,614
Location
Texas
Many of the Qflash models specify 150 watt seconds power. Some models say a bit more.

The SB-900 is at most 75 watt seconds, but probably very close to that.

2 x 75 = 150

These are input electrical power numbers.

The huge factor which must be considered however, is the illumination intensity. The f-stop you use will depend on the angular coverage of the flash reflector. A flash zoomed long to concentrate all of the power into a small area on the wall might be brighter there, than a higher power flash with wider reflector, which is illuminating the entire wall. Area matters, as much or more than power.

We can only compare power levels when both are illuminating the same area.
 
Joined
May 8, 2005
Messages
4,638
Location
Orlando, FL
I have both and the power difference is about one stop, so the two Speedlights together would put out about the same amount of light.
 
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