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Using Guide Numbers in Real Life, and Today's Tangents Article

May I please nerd it out a moment? I'm glad Neil wrote today about back-lighting the sun and Guide Numbers. It's something I've been trying to become comfortable about. Following his books and blog (and shooting Nikon) I know my SB-900/910's guide number is 111.5 at 100 ISO (with the flash head at 35mm). So then at f/11 for example my distance flash to subject will be approx 10 feet. I get that. But then he suggests to cheat a little as you change settings and to use the distance calculated on the back of the flash, in both today's blog and his books, too.

That's where I am. But I use PocketWizards, as does Neil at times. Camera settings and GN's are not displayed with them in use, as he also explains in his blog entries. So when and how exactly is the distance shown on the speed light display? Or is that on-camera only without radio slaves? In other words, what settings do I use to get distance readings on my flash display? HOW DO I CHEAT? I feel like I know how to do the math but don't know how to use the calculator which is a bit embarrassing. TTL is no problem for me, but I'm trying to grow here.

And speaking of math, the guide number is a constant out of the box, right? It's not like I can reverse the algebraic equation and say, "OK, I have an aperture of 4 and my flash is at 8 feet, so I'll program in a GN of 32" and expect to get a correct flash exposure. I mean, that would be too easy. 

These are all elements I'm diving for but keep missing the catch. Thanks for your insights!



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