Considering a Three-Way? Here's What You Need to Know.
They are super-useful, small, light and cheap. Or not, if you mistakenly buy more capability than you need...
For the uninitiated, three-way flash brackets are like an umbrella swivel except they are designed to hold one, two or three speedlights.
A lot people make incorrect assumptions about the power gains to be had by ganging multiple speedlights. In truth, it's the second flash that gives you the bulk of the extra power. Adding flashes after that pretty quickly gets you into diminishing returns.
Think of it in terms of power levels. A flash at full power is twice as powerful as the same flash at half power. But you only get one more f/stop of light. Similarly, ganging two flashes together buys you one more stop of light.
But adding a third flash would only buy you an additional half stop of light from there. (You already have two flashes. To get one more stop you would have to double that and add two more flashes.)
So yeah, you can bump your output by a stop for more power when needed by adding just one flash. Or—and this is usually more important to me—you can cut your recycle time in half by using two flashes and dialing the power down in each.
You can further get power (or recycle) advantages by adding a third flash. But with each added flash the marginal benefit decreases:
One added stop = one added flash
Two added stops = three added flashes
Three added stops = seven added flashes
To get four more stops of light stop, you'd need fifteen added flashes (or, one full McNally.) So, the low-hanging fruit is really from that first additional flash.
For the reed quintet shot, I essentially had two light sources. If memory serves, I shot it at ~ISO 400 at f/8.
I used three flashes in each source, running at 1/2 power. I could have used one flash in each source and shot at full power at about 5.6 and a half.
But by ganging all of my remaining flashes, I could bump up to f/8 and drop my power levels from 1/1 to 1/2. Meaning much faster recycles. So by ganging the lights, I could (a) shoot faster, and (b) start shooting a little earlier in the waning post-sunset light. (I.e., I can start when the light crosses my sync speed at f/8 rather than f/5.6 and a half.)
Even if you have enough power to do what you want, it makes sense to gang lights. If you have an extra flash (or, in this case, five flashes) laying around, gang them with your highest-power-level light to get some extra shooting rhythm.
Which Three-Way to Buy?
Three-way flash brackets vary wildly in price—as in more than 300%. Which model you need is mostly determined by how forward-thinking you have been when you bought your flashes.
Strobies Three-Way Bracket is just $44.99.
(Note that "Strobies" has no relation to "Strobist." Just coincidental.)
Moving up the price scale a little to $60.00, the Lastolite TriFlash is another good, basic three-way flash adapter. I have used both the Strobies and the TriFlash and they are both very strong. The balance is one of size vs. price, really.
The TriFlash is small, rugged and, like the Strobies model at top, totally does the job if your flashes are already synced or slaved. They both pair very well, obviously, with my Nikon SB-800s and LP160s. The TriFlash is small enough where I just consider it to be an umbrella swivel in my bag. It comes with metal springs in the cold shoes which I found to be unneeded. I just removed them.
The Strobies model is cheap enough to just consider it as a regular umbrella swivel. In fact, for the extra $25 it costs when compared to a single flash swivel, I would recommend it as the swivel to buy when you get your second flash (if the flash is slaved). There is no downside to using it for just one flash. And that way, you can always gang your two flashes into one stronger light source.
Downside: It cost more than twice as much as the Strobies basic model. But that's okay, because if you have committed to TTL you are used to paying through the nose for everything sync/strobe related anyway. Why stop now?
It is important to know that there is no extra functionality in the rotating model other than giving you line of sight for CLS-based control.
Lastly, if your flashes do not have an external sync and you want to add this feature to your bracket, no prob. But you will need to dig deep into your wallet for that. At $146.90, the Lastolite LA2455 TriFlash Sync costs over three times as much as the basic Strobies model. But it adds a ganged sync jack and a slave.
The sync is 1/8" (yay) and hard-syncs all three flashes with one remote or cord. It's a pretty sweet setup with a PW, for instance.
The shoes, while hot, do not rotate as with the McNally model. And at more than 3x the price of the basic Strobies model, you are paying yet another tax for not buying a flash with a sync or slave built-in. Just sayin'.
Obviously, my recommendation is to be forward-thinking about your syncing needs when you first buy the flash. As usual, this is money well-spent in the long run and allows you to spend less on the auxiliary gear.
If you have done that, go with the Strobies unit or the basic Lastolite model and enjoy the benefits of more power and/or faster recycle whenever you have an unused flash available. It's a no-brainer.
If you are locked in to having to choose one of the expensive options, it's up to you to decide whether the benefits are worth the extra bracket expense.