Yongnuo YN-560EX (EX600) Review

This is a follow up to my preliminary review of the Yongnuo YN-560EX.  For convenience, I'm going to incorporate the information on the previous review in this one, so this will be the main resource page for the 560EX.

ABOUT THE YONGNUO YN-560EX
The YN-560EX (formerly EX600) is a manual flash but can act as a wireless TTL slave via Canon or Nikon's wireless flash commanders (yes it is cross-compatible with Canon and Nikon).  I was excited about this model because it's only $109.99, less than the YN-565EX (which has wireless TTL as well as on-camera TTL and costs around $160 for the Nikon version).  It is one of the cheapest wireless TTL flashes available.  (At the end of this article I will post other wireless TTL alternatives.)

The YN-560EX should not be mistaken with its similarly-named predecessors, the YN-560 (a purely manual flash) and the YN-560II (an updated version of the YN-560, also purely manual).  The 560EX was previously known as the EX600 but its name was finalized as the 560EX.

Right-Brained Guide to Combining the Guide Number of Multiple Flashes

What's the guide number of two identical flashes?  That's easy enough.  It's about 1.4 times the guide number of one flash.  But what if you need to know the combined guide number of several different flashes with different guide numbers?  That's easy too -- just count the photons.  (I'm just half-kidding.)

If you have two or more speedlights or are thinking of getting a few, and you'd like to know what the combined guide number is supposed to be, I promise that no matter how much you may hate math, you'll be able to calculate it using a regular (not scientific) calculator after the jump.  I'll also promise to use a common sense approach and keep the math minimal.