BDP wrote:
If you are going 640W, then you would be getting the AB1600 which is just too much for most studio/portrait work, and it does not adjust down to as low an output as is possible with the Einstein (which covers the range that you would have to get all three versions of the AB to duplicate). And then it goes a bit lower still, I believe (2.5 w-s).
Yes, Einstein goes one stop lower than the B400 and just as high as the B1600. However, excluding the lowest stop (that cannot be attained by any of our lights) you would not need all three lights to cover the 640-5Ws range. This could be done with the B1600 and B400, as these would completely encompass the B800's power range. Additionally, the X1600 has a 1/4 power switch that lets you choose between the power range of a B1600 or B400, all in one light.
That said, if you can affford an Einstein, then that would be the choice I would recommend as well.