Wednesday, May 18, 2011

The Light Brigade: Multiple Speedlights vs. Studio Strobe

UPDATE: New test shots posted!


Into the valley of death rode the SB-600s...
I was almost ready to take the leap to get a studio strobe.  However, I kept thinking about the limited use I would have for it, given its bulk.  I tried to figure out whether it would be practical to use multiple speedlights instead of a single studio strobe.


Initially, it seems that it would take an inordinate number of speedlights to match the power of a studio strobe.  IIRC, David Hobby estimated that an Alien Bee B1600 with 640ws of power is equivalent to about ten SB-800 speedlights with around 60ws each.

On the other hand, I was only planning to get a B800, which rated at 320ws.  That would be around five speedlights.

And if we were willing to get 20% less power (about half a stop reduction), then four speedlights would theoretically suffice to get somewhat close to the output a medium-powered monobloc.  Interestingly, this site http://www.scantips.com/speed2.html says that behind an umbrella, an SB-800 speedlight (at 24mm zoom) has about 2 stops less power than an Alien Bee B800 studio strobe (with a 7-inch reflector).  To bring a speedlight up by 2 stops in power, we would need ... let's see... four speedlights!

Then last week, we also learned that calculating the combined GN of multiple speedlights (even of varying power) is fairly easy if you know how.  And at least on paper, four speedlights (SB-800, SB-26 and two SB-600s) can give a GN of about 220 feet, almost the same as an Alien Bee B1600 with a 7 inch reflector.

Four speedlights seems right at the edge of practicality (both use and cost).  I know three is commonly used by a number of pro photographers (such as in these great examples by Louis Pang and Syl Arena) so that's definitely possible.  Of course there's also Joe McNally with his Tree of Woe, and Archimedes with his mirrors, but I would venture to say that they're outliers.

Why go through the trouble of using multiple speedlights?  One advantage of having four speedlights instead of one studio strobe is that the four speedlights can be used separately if necessary.  That's one trick a monolight can't do. :)  Here are other potential advantages as described by David H.

BRACKET OPTIONS
One of the first issues we have to deal with when using 4 speedlights is how to mount them on a light stand.  There are a few bracket options in the market such as the Lightware Direct FourSquare and the aforementioned mod of the Brewer bracket.  

Here's a DIY version I made that I like better because it's a more compact arrangement of the 4 speedlights:


To put this together, you need two brackets like this.
You don't need the umbrella riser (as long as you have a way to keep the middle thumbscrew from moving around), so you can buy the $17 version. And if you have your own coldshoes or prefer to use your AS-19 stands, you can even get the $10 version that has only the bracket and thumbscrews.  In an emergency (like a sudden attack of cheapness), it's possible to use just one of these brackets plus some ball bungees, though there's a chance you could drop one or more of your flashes.

You also need a ballhead if you want to use the quad-flash with an umbrella bracket (so you can use an umbrella).    If you somehow want simply to blind your subject with bare quad-flash, you could skip the ballhead and just use the umbrella bracket to angle the quad-flash at 90 degrees.  (P.S. Remember to take your medication for miseritis).

I started assembling mine by mounting two flashes on the bracket, each at around a 30-degree angle.

I then placed the other two flashes between them, and bungied them up.  
If I had another bracket, at this point I would attach the second bracket to the first via the middle thumbscrew, then secure the latter two flashes to the second bracket.

Here are some more views of the assembled quad-flash:




The total weight of this quad-flash assembly, including the bracket and batteries is about 5 lbs. (of course this will vary with the types of flashes you have).

TRIGGERING OPTIONS
Another challenge when using quad-flash is how to trigger the flashes and if possible, remotely adjust them.  There are many ways of doing this, depending on what flashes you have and how much you're willing to pay.  Here are some possible arrangements:

  1. If you have a commander flash and the flashes are slave-capable: trigger and remotely adjust them via your commander.
  2. If one of the flashes is commander-capable and the others are slave-capable: use an extra-long TTL cord to control the commander flash while using the others as optical slaves.  This option works better for Canon if you have a flash that can be controlled by the camera's menu.  For Nikon, we're limited to using the FEC to adjust the whole group.
  3. If all the flashes have TTL quench pins: use a Radiopopper JrX Studio to trigger and remotely adjust them in manual mode.  You don't have to buy 4 JrX Studio receivers.  Instead, just buy one JrX Studio receiver, then daisy-chain these RP Cube substitutes by ebay seller bufo1955.

POWER COMPARISON (IRL)
Barely a week after I got two more flashes for this quad-flash arrangement, guess what happened?  I came across a really good deal for an Alien Bee B1600.  As an Asian guy who can't pass a deal like that, I snapped it up.  So how does the power of the quad-flash compare with that of a B1600 with a 7-inch reflector?  I took shots of a brick wall at 10 ft, f/22, at 1/250 (yes, people, besides being reduced to a gear collector, I am now shooting brick walls! :) ).

I took the shots outdoors so there was no chance for any extraneous bounce.  The B1600 was triggered with an MK-RC7 (1st generation) radio trigger.  The quad-flash was triggered with a TTL cord to the SB-800, and the TTL cord was daisy-chained with AS-E900s for each of the other cameras.

Here are the unedited JPEGs straight out of the camera:

B1600, f/22, 1/250, 1/100, 10 ft from wall
Quad-flash, f/22, 1/250, ISO 100, 10 ft from wall
Note that the color temperature of the quad-flash shot is warmer.  That's because in the case of the B1600, the camera did not know that there was a flash being triggered (the radio trigger is completely manual).  In the case of the quad-flash, the camera was connected via TTL cord to an SB-800, therefore the camera was aware that there was a flash, and in Nikon's system, the camera corrects for the flash's color temperature (in fact, in the case of the SB-900, the camera can correct even for the use of gels if you use the official Nikon gels).

MODIFIERS
With this quad-flash, your choice of modifiers will be more limited than either with a single speedlight or with a studio strobe.  You could use:
  • a scrim/diffusion panel
  • an umbrella (however, very small umbrellas may lead to excess spill)
  • possibly a softbox - a Westcott Apollo, due to its unique configuration, may be usable with this quad-flash, except that the flash heads would be set to their 0 degree position (instead of 90 degree position).
  • bounce from a reflector or other surface.
CONCLUSION
Given the power discrepancy, the cost of multiple speedlights, potential challenges in controlling the flashes, is it worth using a quad-flash instead of a monolight?  To help you answer that I will be discussing using the studio strobe from a family photographer's perspective.

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