Paul C. Buff, Inc. Technical Forum

Any estimate as to what the guide number of an Einstein with the white 86" PLM as a shoot-through? Full power at 10 feet @ ISO 100 outdoors.

Tia.

Mack

ISO 100 white PLM at 640Ws should yield about f/8 at 10 feet, assuming there is no cover to assist in redirecting. This is true for bounce or shoot through.

Remember, when outdoors, ambient light can introduce a significant amount of additional light that would add to this exposure.

I'm interested in this as well. How much better would it do with the spill kill cover? Or, does it preform any differently at all.

Yes, I already recognize the added advantage of not having all of that reflected light pouring out of the back of the umbrella.

Adding a black outer cover or a spill kill fabric will add about a stop vs all else being equal but without these fabrics. So, f/11-ish at 10 feet.