Thursday, May 31, 2012

Sunny 16 and PW's Hypersync

Recently, I was fortunate enough to be able to beta test another cool product from PocketWizard.  This time it was their newest transmitter module for the Sekonic L-358 meter.  The product is called the RT-32CTL and it is called that because it can trigger the latest ControlTL units on channels other than the standard 4... indeed, it can work on all 32 channels, hence the name.

An amazing tool, it makes precise metering of your subjects a BREEZE except that now your triggers can be the ControlTL units... something that was previously not possible and is quite honestly... wonderful.

I've wanted to add this small transmitter to my list of tools for quite a while, but since I decided to walk the path of the ControlTL units as my triggers of choice, unfortunately, the original Sekonic transmitters were not compatible and could not speak to the new ControlTL units.  Triggering flashes connected to FlexTT5 units via Sekonic meters  was not possible... until now.

Yesterday I received my beta copy of the unit and since I had some testing to do, I decided to have some fun looking over the performance of the latest beta firmware for the ControlTL units (which is needed if you wanted compatibility with this new Sekonic transmitter).  The new firmware, besides adding the additional feature of being able to work with the new Sekonic transmitter, also added the D4 to the list of compatible cameras and then a host of other changes.
Cool... another reason to do some testing and playing!

So, the scene was set, but let's define a few things.  The equipment used was:

- Nikon D4

- Nikon SB-80dx (this is my workhorse flash when I want to beat on it at full power.  If it dies, better that one then the SB-600, SB-800 or SB-900 in my kit!)

- Hypersync values were set to -1200 at the remote FlexTT5 (maybe not optimal, but should be close enough)

- Fixed distance of 10 feet from lightstand to wall (fair distance if someone wanted to do something like roughly a full body shot of 2-4 people

- Flash head height exactly 5 feet from floor (which places the flash head just underneath my chin level... just a kind of marker becuase in later testing, I shall always place the Sekonic meter under my chin as the starting point.  In real life, we always want the light to be coming from a higher angle for more realistic results, but that's not what we want to play with today).

- Flash head is zoomed to it's widest setting of 24mm and that is without the wide angle diffuser dropped down into place.  With that small plastic flap down, light would travel as wide as 17mm, but we would lose some light, so for now, up it stays.  Thanks to the limited power of a single flash, it may be more important to zoom in more than wide anyways.  Zooming in increases the amount of light by an amount we shall discuss later.

So this was the basic starting setup to do some tests.  The flash was sitting on a hotshoe adapter and connected via standard sync port to 1/4" mono plug sync wire to the P2 port of the FlexTT5.  Manual Hypersync settings will not work if the flash is sitting in the hotshoe of the Flex.
Installing the transmitter module into the Sekonic meter was very simple, just make sure it is turned off, open up the back, remove the protective plastic cover that hides the connectors, carefully pop in the module, set it to the proper channels, then set it to the proper mode and you are ready to use it!
The Sekonic meter only goes up to 1/1000th in it's settings, but calculating resultant F-stops needed for 1/2000th, 1/4000th and 1/8000th shutter speeds is not very challenging, so it works just fine.
I also want to answer a few questions such as:

- How much power will a standard umbrella eat in terms of power? 

- How much more power can I get if I use a higher zoom setting, and how is the shot affected if distance between flash and wall remains 10 feet?

- If I use that plastic diffuser panel and get the zoom to 17mm, how much do I lose and again, how is the shot affected if distance between flash and wall remains 10 feet?

A couple more factors... I decided to stick to 1/1000th shutter speeds for the tests, and then started thinking... how does this work with the Sunny-16 rule? 

Oh... that rule.  This one gave me a bit of a headache.

You see, the exact specs of what the Sunny-16 rule entail come from the days of film and my research tells me that though shutter speeds and ISO vary quite a bit and no one can tell you what the definitive numbers are, the most common variant of this rule is:

"On a bright day, one sets their film camera's shutter speeds to 1/125th, apertures to F/16 and ISO to 100."

Ok, honestly, in today's digital world, it is no big deal if we talked ISO 200 or shutter speeds of 1/250th, but we do need a starting point, so the F/16 - 1/125th - ISO 100 will be our starting point here today for this discussion.

Right... I bet you guys are all fed up with me by now and are thinking "press the darn button on the meter and tell us what a single flash is capable of already!"... ok so let's do it!

With the bare flash a measured 10 feet from the wall and 5 feet from the ground, we meter to a very nice F/6.3 at 1/1000th.

That means that if I wished to shoot at F/4.5, my shutter speeds would be 1/2000th or F/3.2 at 1/4000th or 1/5000th at F/2.8.  In real world terms, it also means that I should be able to frame out an area that would let me light 4 people wide at around 6 feet high easily enough.  But the real question that everyone that wants to use HyperSync is asking right about now is... is this enough light to be able to be useful on a bright day?  If so... by how much?

Let's look at these numbers.  Let's just start off with shutter speeds.  The Sunny-16 rule uses a 1/125th shutter speed and we are using a 1/1000th shutter speed for our tests.  That is a 3 stop difference (125th>250th>500th>1000th). 

Ah, but our aperture was F/6.3 at 1/1000th... how do the apertures work out?  Well, to keep it a little more accurate, we'll stick to 1/3rd stops and see how many stops it is from F/16 to F/6.3... and that is exactly 2-2/3rds stops different. 

In the real world, it is very hard for us to see a 1/3rd stop difference so for all intents and purposes, we have just defined the fact that if I use a single Nikon SB-80dx speedlight at full power, then if current conditions are as the Sunny-16 rule states, we can light up an area big enough to fill flash a group of 4 people, pretty much from head to toe (though not 100% evenly). 

But what if I wished to overpower the sun (which conveniently was just at the Sunny-16 level of strength)?  Well, since we cannot make the sun weaker (well, we could by waiting, but let's pretend that you don't have the time to wait, and need to get that shot now), that is out... but we are 10 feet away from our subjects.  By placing the flash closer, the light becomes stronger.  We also have the flash head zoom and that also can add some extra light to the shot.

Let's start with the zoom head.  At our first test, it was set to 24mm, so in the next tests lets see what happens when we set it to different zoom levels:

At 24mm we got F/6.3
At 50mm we got F/9
At 85mm we got F/10
At 105mm we got F/10

That is some valuable info!  The design of the SB-80dx gave us the equivalent of 1 full stop of power by going from 24mm to 50mm.  Amazing, because that is the equivalent of doubling the flash power!

By going from 24mm to 85mm, we gained 1-1/3rd stops and by zooming it all the way to 105mm, we realize that the design of the flash did not offer us anymore power after that.

Just for the sake of comparison, when the Nikon SB-900 flash was measured at different zoom levels, the numbers were:
At 24mm we got F/6.3
At 50mm we got F/8
At 85mm we got F/9
At 105mm we got F/10
At 200mm we got F/10

... so we see that the SB-80dx stacks up well in the maximum power department, however, it obviously lacks other features that are very important to me, such as iTTL support and ability to act as a commander for 3 groups thanks to CLS.

OK, back to overpowering the sun... what did zooming give us?  Well, by zooming from 24mm to 50mm, we clearly now have the ability to overpower the sun by 1 full stop.  That means that if we wished to shoot at F/2.8 for those nice blurred out backgrounds during the day, we would need a shutter speed of 1/5000th, but because we had more light, our subjects would be overexposed by 1 stop, so, we would change aperture to F/4, the entire scene would drop by one stop and our entire background (or anything not lit by the flash) are suddenly 1 stop darker.

We've just overpowered the sun by one stop.

But wait, we have one more tool to play with... distance of flash to subject.  Remember, this is all happening at 10 feet apart.  What if we decided we wished to do a head and shoulder shot of ONE person or a couple very close together, and moved that flash to a distance of 5 feet?  Those that know the Inverse Square Law will likely know how to calculate exactly what the results will be, however, I will do it the manner that strains my brain less, and simply move the lightstand to the 5 foot mark and press a button on the Sekonic meter.

The results were:  F/13 at 1/1000th at ISO 100 with the flash set to 24mm.  However, we are lighting a much smaller area, and perhaps we don't want a 24mm spread of light... so what happens if one zoomes the head to 85mm?  Setting the zoom to 85mm, and the meter reads out a  blinding (LITERALLY for your clients!) F/18 at 1/1000 and ISO 100!

From our start of F/6.3, to an impressive F/18... that is an increase of 3 entire stops.  Wow!

So, if we are matching the Sunny-16 rule at F/6.3, ISO 100 and 1/1000th, well, now we know that we can overpower the sun by at least 2 stops under very controlled conditions with a single battery powered speedlight that is near 30 years old.  However, let's be honest... it won't be very comfortable for the people that are 5 feet away from your flash, and you will be limited to something tighter, like a head or perhaps a head/shoulder shot at most.

But what if you wanted to shoot at a shallower DOF?  Well, if you went to 1/8000th shutter speeds, aperture would drop to F/6.3, but if you used a longer lens and/or increased distance of subject to background, you could achieve a good amount of background blur (though to be honest, that background is going to be at least 2 stops darker!), but the amount of blur is defined in not just one aspect, but five.  To understand what those five control points that create background blur are, refer to my article here called "DOF, The Advanced Look".

Oh, I almost forgot to mention... adding a standard 43" umbrella to the flash setup ate a full 2 stops. I always thought it was less than that, but that is exactly what my umbrella munched up, as per the meter reading.

Remember that small plastic flap that increases zoom another few degrees?  It dropped the light from F/6.3 down to F/4.5... a drop of one full stop.  Now, though it did lose a full stop, it also increased the width of the lit areas a little more than the small increase from 24mm to 17mm would suggest.

All good info to know!

Epilog:  All the numbers that I used in this article were made available thanks to my Sekonic meter and the new PocketWizard transmitter module.  Again, what a great tool... I know that I now have a wonderful new addition to my kit that is going to help me make better metered and balanced lit photos in controlled conditions.  Also, because I have hard numbers now, I better understand the limitations and capabilities of speedlights and how they function under very specific conditions.