I did a quick test this afternoon to see how the Einstein's various reflectors would perform with one of my 43" Steve Kaeser umbrella boxes. The test setup was simple, I just set the Einstein to -5.5 stops power output and photographed the front panel of the umbrella using the Spill Kill reflector, the PLM reflector, the 8.5" grid reflector, and no reflector at all.
Here's the Einstein and the Steve Kaeser umbrella box:
And here's a composite of the test results:
I don't know about you, but I would have expected less hotspotting with the Spill Kill reflector and with no reflector at all. A pronounced hotspot is always in evidence.
The PLM reflector is oddly shaped; like a small, round deep-dish pizza pan. The pattern it threw is not surprising. The 8.5" grid reflector also performed as expected. I felt it was fair to include it in the comparison since it does have a hole in it for an umbrella shaft to pass through.
Based on this test, it would appear that the Spill Kill reflector is indeed the best bet for umbrella use. That it doesn't really out-perform the 90-degree Elinchrom reflector is surprising (to me) but not a problem. When flash power is raised to more practical levels, the hotspot is no longer visible. Here's the umbrella face at -2 stops power output level:
Note that the Einstein is performing in this umbrella test very much like all of my other lights have performed. That is to say, it produces a central hotspot that will undoubtedly have no adverse impact in real world usage.
Dave F.