Sony's New Wireless Flash Protocol

With the introduction of the HVL-F58AM flash, Sony has completely revamped the wireless flash protocols -- the time between pre-flash and exposure has been shortened, and more addressing capabilities have been added.  The result?  Automatic Ratio mode has returned (this feature worked with film cameras brilliantly, but was disabled in digital bodies for technical reasons), and now you can control up to 3 banks of flashes (well, sort of) from the rear of the 58.

Okay, but how does it work, and how much of it is backwards-compatible with the Minolta / Sony 56 and 36 flashes?  Can you mix and match the 56/36 and 58/42 flashes?  Read on to find out!

Reading Sony's documentation to learn the answers to these basic questions can be a frustrating experience.  (In Sony's defense, it wouldn't have been nearly so complicated had Sony not tried to be backwards-compatible with their older 56 and 36 flashes.)  So here's a summary of some basic truths that are essential to know if you are going to be using wireless flash with the A900 (or A700 with Firmware Version 4) and the 58 as the wireless flash controller:

• The basic wireless flash protocol has been completely revamped and is incompatible with the older system.  That means if you set a 58 on top of an A900 or A700, it won't be able to trigger your 36 or 56 out of the box.  (Or at all if mounted on any other camera.)  Sony calls this new, incompatible system "Control +" and is the factory default.
• The older protocol is simply called "Control", and is required to trigger the 36 and 56 flashes.  Only the A900 allows the 58 to work using this mode.
• As wireless slave flashes, the 58 and 42 work just swimmingly whether they're being triggered by a pop-up flash from a Maxxum 7 (old protocol which used HSS; older cameras won't work) or by a 58 in "Control+" mode.  Just set them to wireless mode and let them go.
• However, if you want to use the older 56 or 36 flashes as a slave, you have to put the A900-mounted 58 into the "Control" mode (so it sends the old protocol).  To do this, set the 58's Custom Function 3 to "CTRL2".

So all these modes and compatibility issues might seem a little daunting, so here's something to make it clearer.  Below is a diagram showing the simplest configuration possible for wireless flash:

Notice that with this configuration, illumination for the subject comes only from the slave flash.  (The Master only sends out Morse-code-like commands using weak flash pulses, and doesn't affect the exposure significantly.)  And the 58 has been put into the old-protocol "CTRL" mode so it can readily trigger any wireless flash you may have (36, 56, 42, or 58).

Next, let's talk about groups and ratio flash.  First, here's a quick recipe for ratio flash:

(Things don't look so intimidating in diagrams, do they?)  This setup is identical to the previous diagram, except that "Ratio" mode on the 58 has been enabled.  In this mode, light to illuminate the subject comes from both the slave as well as the master, and you can control the proportions from the back of the Master.  Dialing in a ratio of 1:4, for example, means that the slave outputs four times as much light as the master.

Finally, let's figure out what's involved to achieve Sony's Marketing claim of "Up to three groups of flashes can be set up for optimal, complete control of lighting via a wireless connection".  Here's how to do it:

With this setup, illumination comes from all three flashes (plus the control signals from the master, which don't affect exposure significantly).  Here are the salient points about this setup:

• The Master flash was put into "CTRL+" mode (by setting Custom Function 3 to "Ctrl1").
• The new flash added to the bottom can ONLY be another 58 flash, as the 58 is the only flash on the planet that knows what RMT2 (Remote 2) mode is.
• The rightmost flash can ONLY be a 42 or a 58 - none of the legacy flashes will respond when the master is set to "CTRL+".
• Notice that Sony treats the Master flash on top of the A900 as a "Group".  (!)

So now, dialing in a flash ratio of 1:2:8 means that the RMT flash is twice as bright as the light from the master, and the new RMT2 flash is 8 times as bright as the master.  Don't want light coming from the master?  Then you can dial in "-:2:8" and the Master will only put out control signals.

Flashes literally become groups when you have more than one configured the same way:

So that's the new wireless flash in a nutshell.  Now that the basics have been laid out for you, you can now go back to that cryptic flash manual of yours and figure out how to set CF3 and ratio modes (or just buy my book when it comes out :-) ) and the rest of it should make a great deal more sense, too!

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