How much brighter are studio strobes than speedlights?

Started May 12, 2013 | Discussions thread
WFulton Senior Member • Posts: 2,695
Re: How much brighter are studio strobes than speedlights?

Brent Allen Thale wrote:

Comparing histograms, the 1/8 power X2400 shot plus 1/3 stop looks about the same as the full power Nikon SB-900 shot. So the X2400 is not quite 3 stops more powerful than the SB-900. Does that sound about right? I suppose 3 stops is a lot, but I was expecting a bigger win for the X2400.

A larger speedlight (like the SB-900) is about 75 watt seconds.  A smaller one (like SB-600) is more like 60 watt seconds.  Each time you double the watt seconds is one stop.

But speedlghts zoom, like from 24 mm coverage to 105 mm coverage or more.  When the light is concentrated into the much smaller beam, it is of course much brighter than when zoomed much wider.  Is it illuminating a spot on the wall, or the entire wall?   This angle of coverage may matter more than power level.

You can only compare them when in the same modifier, like in the same umbrella (and of course, at the same distance).  Same angular coverage is necessary, else you are fooling yourself.  It is more of an "illumination per unit of area" concept.

The speedlight at 24mm zoom covers 78x60 degrees (spec chart in rear of flash manual)

The studio light probably specifies the coverage, but it may be more like 80 degrees coverage.

It definitely takes more power to fill 80 degrees than 78x60 degrees.

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