Paul C. Buff, Inc. Technical Forum

I'd like to ask how angular coverage of AB reflectors is determined. The 7" reflector is specified as having an 80-degree spread while the 8.5" is specified as a 45-degree spread. Since neither reflector projects a perfect disk of light with a sharp cutoff at the boundary, I would imagine angular coverage is based upon light intensity being a certain number of stops down at a certain number of degrees off axis. The question, then, becomes how many stops down does AB use as its standard for computing angular coverage of reflectors and is that standard applied equally to all AB reflectors?

Dave F.

Dave, you're thinking too much. Go take some pictures!

You are exactly right, it is how many degrees off center. Our stats are for -1f, which is my understanding to be standard. You also must take into consideration the curvature of the distance from the flash head. You cannot set a flash up 10' from a wall, and take measurements along that wall, since the further out you go from center, the farther you get from the light.

Excellent! Thank you, TS. So it's -1 stop (and, yes, I understand the need to keep the radius constant).

Ziv: You're absolutely right. I do think too much sometimes (often). I will take your advice and grab the camera if it ever stops raining here in New York.

Dave F.

I figured you did. However, lots of people lurk here, who may not understand that. If they get as much information upfront, it helps reduce confusion on the back end. An ounce of prevention, if you will.