Comparing monolight strobes

I admit it! I have a mixed variety of monolights. I've got a Speedotron Force 10, an Alien Bees Ring Light, and a few SP Systems Excalibur 3200 and 1600 units. I try to not mix them together on the same set to help maintain color fidelity. But I decided to test them all out to find out just how different the color temperature of each is and how consistent the color is when dialing down the power. (Am I the only person out there who wants less strobe power or lower ISO cameras? I would like to have a good ISO 50 or 25 available. Higher ISOs with less noise is OK, but I'm often going in and adding grain.)

Anway, this isn't a scientific test, but I think it will work for my needs. I set up a Greytag Macbeth Color Checker and a WhiBal card at about 5 feet from a light stand. Took a series of photos at full power, 1/2, 1/4 (or -1, -2), etc. with each head. 7" standard reflector on the Excalibur and Speedotron, the 10" ring reflector (no diffuser) on the Alien Bee. I then opened all the files in Adobe Camera Raw 5.2 and used the White Balance tool to read the WhiBal in each image and wrote down the color temp and tint that resulted.

Here are the results:
Power Setting
ColorTemp Adjusted To
Tint Adjusted To
SP Systems Excalibur 3200
Full Power
5150
-4
1/2 Power
5000
-6
1/4 Power
4900
-8
1/8 Power
4900
-8



Alien Bees ABR800 Ring Light
Full Power
5550
-10
1/2 Power
5500
-12
1/4 Power
5400
-12
1/8 Power
5350
-15
1/16 Power
5250
-16
1/32 Power
5200
-19



Speedotron Force 5
Full Power
5350
-8
-1
5250
-8
-2
5250
-7
-3
5150
-10
-4
5100
-12
-5
5050
-15

As you can see, they are all pretty consistent. The color of the light goes slightly bluer (requiring a little bit more yellow compensation in the Color Temperature scale) as the power is lowered. I believe that is to be expected.

I also metered all three heads in the same configuration at 5 feet at full / minimum power:

Excalibur: 22 / 8
Alien Bee Ring Light: 32 / 5.6
Speedotron Force 5: 32 / 5.6

I won't list the watt-second ratings, as I don't think that number matters much, especially when comparing different brands of strobe heads. Watt-seconds measures how much energy can be stored in the capacitor. It doesn't really tell us much about the efficiency of the system.

Bottom line, I'm happy with all of these products.