This weekend I got the chance to compare the power output and light quality of four different models of studio strobes (and a speedlight too, just for kicks). I compared the Photogenic PL1250 ($500), the AlienBees ABR800 ringflash ($400), the AlienBees B800 ($280), and the Calumet Genesis 200 ($170). I could have thrown an old White Lightning Ultra 1200 into the mix, but that's a discontinued model, and I figured I was doing enough testing anyway. I used my trusty Nikon SB-800 as the speedlight for comparison.

How (and what) I tested:
I placed the strobes on a light stand about 20 feet from a gray wall, and swapped out the lights one at a time. I kinda wish I had a tape measure, but the gray floor was a bit shiny anyway, and I was really only after the relative differences anyway. Basically, these numbers represent the kind of power you can expect to get out of these strobes at what I would consider to be somewhat far working distances.

I placed a light stand right up against the target wall and set it to the same height as the strobes. I used a Sekonic L358 flash meter with the dome retracted and the display set to 1/10 increments. I held the flash meter at the top of the light stand and fired each unit a few times to make sure the readings were consistent to within 1/10 of a stop.

I tested each strobe at full power in at least two basic configurations - bare bulb, and with their standard reflectors. I tested the speedlight at full power at various zoom settings. I also tested a few different modifiers on my ringflash since I had them handy and was curious to know how each one affected the power output and light quality. I took photos of the wall and the light stand in front of it to visually compare the color temperature, beam spread, shadow quality (light quality), and overall power output. I'll have to post the photos later. I did not attempt to measure recycle time, flash duration, or output consistency between shots.

How to read the numbers in this table:
Metered power is given in 1/10-stop increments. 5.6 7' is read as f/5.6 plus 0.7 stops, which ends up being about f/7.1.

Code:

                    Street    Power in W·s 
                     Price   (Manuf. Spec.)
AlienBees B800        $280        320
 Photogenic PL1250     $500        500
Calumet Genesis 200   $170        200
AlienBees ABR800      $400        320

So, judging by the numbers above, we'd expect the output power of the two AlienBees units to be nearly identical. Assuming we use each of them in bare bulb mode (i.e., no reflectors), the numbers indicate that the Bees should be about 2/3 of a stop brighter than the Calumet, and about 2/3 of a stop dimmer than the Photogenic model. Since most people will end up using the strobes with their default reflectors, I have included those numbers here as well.

Code:

                     Bare Bulb    w/ Reflector
AlienBees B800         2.8 7'         5.6 8'
Photogenic PL1250      5.6 3'        16.0 6'
Calumet Genesis 200    4.0 9'         8.0 0'
AlienBees ABR800       5.6 4'         8.0 3'

Let's use the B800's power as a zero-point for comparison, since it's such a popular unit. The numbers below indicate how many stops brighter (or dimmer) each unit is compared to the B800. Positive numbers mean that the unit is more powerful than the B800, and negative numbers mean that it's less powerful. It's important to remember that the flash tube in the ABR800 is mounted on a mirrored and slightly curved surface which acts as a reflector, so "bare bulb" in that case is a little misleading. On the other hand, it's still got bare bulb light quality, so it's not completely unfair to directly compare the numbers.

Code:

                     Bare Bulb    w/ Reflector
AlienBees B800          0.0            0.0
Photogenic PL1250      +1.6           +2.8
Calumet Genesis 200    +1.2           +0.2
AlienBees ABR800       +1.7           +0.5

Once the reflectors are placed on the units, the ABR800 loses its huge advantage over the B800, but you still end up with a half stop more power (and better light quality to boot). The Genesis also appears to lose most of its advantage in power output, but once I upload the photos, you'll see why the numbers here are a little deceiving (it's more powerful, but the light distribution is crap). I expected it to have an even bigger advantage since it appears to have a parabolic reflector (although it's got some weird ridges going on). The Photogenic widens its lead by a whole extra stop, thanks to the fact that its standard reflector is parabolic and not conical like the AlienBees. A properly designed parabolic reflector = more power, less beam spread/spill, and better light distribution.

Here's how the various modifiers for the AlienBees ABR800 ring flash impact its power output:

Code:

ABR800 with...               Power (metered f/stop)
Bare Bulb                      5.6 4'
Std reflector w/o diffuser     8.0 4'
Std reflector w/ diffuser      8.0 3'
20 degree honeycomb grid       5.6 7'
Bare moon unit                 8.0 0'
Moon unit w/ inner reflector   5.6 7'
Moon unit - fully assembled    5.6 4'

The moon unit is as efficient as using it in a bare bulb configuration, and you only lose about one stop of light compared to using the standard reflector (in exchange for much softer light).

And here's the numbers for my SB-800 (~50 W·s?) for comparison. I wish I had remembered to test it with the 18mm wide-angle diffuser, but oh well.

Code:

Zoom setting   Power  (metered)
24mm           4.0 8'
35mm           5.6 4'
50mm           5.6 8'
85mm           8.0 2'
105mm          8.0 3'

That took entirely way too long to write up. Photos will be up either tonight or sometime later this week (along with wildly inaccurate color temperature information). I was honestly shocked at how little power the B800 had. I will probably try to do another heads-up comparison between my Photogenic and a different B800 to see if it was just a bum unit or something.

Basically... I'm really glad I hopped on the cheap Photogenics when I had the chance, and I'm quite happy with my ABR800 as well.

And here's the images: (huge photos are huge - sorry)

Light pattern comparison (each shot was captured using the metered exposure)


Power output comparison (each shot was captured at f/11)