Answer: 4-1/3 stops, or more, flash power.

It might seem like an obvious idea at first that if you want a black background, you need black background paper or the inverse for white. The truth is that the color and brightness of the background has everything to do with light on it and almost nothing to do with color of it.

In fact, if you haven’t already, it might be best to make two major shifts in thinking about backgrounds.

First, background materials on need to be neutral colored. In general, there’s no reason to buy colored background papers. Muslin backgrounds, because of how they’re used, are a different story. When it comes to rolls of background paper, you can do virtually anything with neutral grays, specifically black and white. If you want color, gel your background light the color you want and blamo, instant colored background. Better yet, using this you can generate colors that are far more saturated than the background paper ever could be.

Second, since the background is neutral in color, its tonality controls how much light it reflects, not its color. Color becomes a mechanism for controlling light not actual color. This is the root of the question that started this article, and the meat of what I’m going to talk about. This is actually in important mechanism for controller spill, and isolating background colors.

Like most things in photography, choosing the background is more about balancing one of the 10,000 variables you have to deal with than anything else.

First up are two shots of a camera on a black background. The first was shot with a black background paper, the second with white. In both cases, the “front surface mirror” was black acrylic[i].

Black background paper, thought it doesn't really matter since the background light is off the background will be black no matter what.

Similar in appearance to the pure black example, but in this case the background paper has been changed to pure white. Again, no light on the background means a black background in the final image.

On the flip side, the following two images with “light” backgrounds are shot again, one with black and one with white background papers.

At f/16 ISO 400, it takes a full power burst from a Canon 580Ex II to get even this much "brightness" in the background, but if you have the power, you can go all the way to white.

At f/11 ISO 400, it only takes a 1/32 power burst to get a background similar to the full power shot against a black background paper.

Could the backgrounds been lighter in the second set? Sure. However, this where I go back to what I said, about color controlling, namely black, controlling flash power. The difference between full power yields gray at f/11 to 1/32 power yields gray at f/11 is exactly that. That’s the difference.

For this article I shot a product, and a small one at that, instead of say a model, but there’s no difference stepping up to a larger subject other than increasing flash power and controlling how evenly the background is lit. Actually, stepping up to a model in some ways makes things more flexible, since a wider aperture will drop the flash powers needed to light the background significantly.

Flash extenders are normally used when the subject is at long distances, even with a 400mm lens. At short distances, there is a good chance that due to the increased flash power, the camera won’t be able to drive the flash at a low enough power.

The standard zoom setting for most flash extenders is 50mm. Adjusting the flash’s zoom position will still change the size of the projected beam, but not necessarily in the way one would expect.

• Widening the zoom (i.e 28mm instead of 50mm) will produce a narrower beam with the extender attached.
• Increasing the zoom (i.e. 85mm instead of 50mm) will produce a wider beam with the extender attached.

The first time I tried wireless flash triggers, they were unreliable and that was being kind. Whether it was RF noise from the flash or some strange sync issue, they were so unreliable for me it wasn’t worth trying to use them. It didn’t take me long to get a pair of LPA Design’s PocketWizard Plus 2s. When I finally got around to adding a second flash, the radio trigger market was poised to go TTL; Radio Popper had their first TTL system out already and Pocket Wizard wasn’t far behind. Instead of springing for another Plus 2, I elected to save the money and wait for Pocket Wizard’s TTL system whenever that came out. It was out of that necessity and experimentation that I figured out how to get working completely wireless two light setup with only 1 pair of radio triggers.

Required Materials

• A Canon Speedlite capable of being used as a ETTL Master flash (i.e. 550Ex, 580Ex, 580Ex II, ST-E2, etc.)
• 1 or more Speedlites that can be slaved under Canon’s ETTL wireless system.
• A pair of radio triggers (or a PC Cord)
• A basic PC-cord to hot-shoe adapter

What you need. (Shown: 580ex II master, 430EX Slave, Hotshoe to mini-phone for master, 2 RF triggers.)

The Setup

Mount the master flash in the PC-cord hot shoe adapter and connect the adapter to the RF receiver (or the camera via a long PC cable). Set the master flash to wireless master mode.

Canon 580Ex II in master mode on light stand connected to Pocket Wizard Plus 2 via hot shoe adapter.

Set the remote flashes to slave mode the same as you would if you were using an on camera master. Place them where you want them.

What Works, What Doesn’t, and What are the Limitations

First off, TTL does not work. This is not a TTL setup.

Remote manual power control and stroboscopic mode do work, so long as the master supports them. A 580Ex II will drive any other slave-able Canon flash in stroboscopic mode.

The largest limitation is in sync speed. I found on my EOS 40D that I was limited to about 1/160^th instead of 1/250^th. Using the master to control the power of the remotes hits the sync speed even harder. The best sync speed in this configuration is reached when the master flash is set to group a, with no ratios and the slaves control their own power levels.

Conclusion

With the availability of more reliable cheap wireless triggers, this technique isn’t very useful any more. It’s made even more redundant by the availability of very good RF TTL triggers like Pocket Wizards’s ControlTL system and Radio Popper’s X system. In short, it’s probably not worth bothering with this unless you’re in a pinch and don’t have any other backups available. I certainly don’t use this any more.

From start to finish it took about 2 hours to get everything setup, designed, groomed, ready to go and shot. Fortunately, I already had my lighting designed so it was a matter of quickly dialing in the power settings. The real chore was herding popcorn where it needed to be.

The setup overview image below, shows the general overview of the setup I came up with. The background was a readily available blanket that I tend to favor when I need a dark background to paint with light.  It has raised ribs in it so the background takes on some texture but doesn’t overwhelm the image.

Setup Overview

The popcorn scene was setup (well it had been taken down when I shot the setup shot) on a piece of black corrugated plastic (so as not to get a sheet of foam core all buttery). That was placed on top of a tub (seen on the couch) to raise it a bit higher and give me some room to work and hide one of my two flashes under and behind the subject. Having the second flash on the table turned out to be helpful, as I was one lightstand short of what I needed.

Now to dial in the light; this turned out to be my biggest limiting factor in many ways. I started with the main light at 1/16th power and the background light at 1/8^th power. Since the 580Ex II is about a stop more powerful than the 430Ex; at equal powers the flashes will have a 1:1 ratio between them even though they are set differently.

I’m often asked how I figure out my exposure settings–aperature and shutter speed–for any given shot…

See how after the jump…

Lighting Tests

How I Figured Out What Settings to Use

The first thing you have to consider is what your most important exposure setting is. Are you shooting a static subject from a tripod? Or are you shooting moving things hand-held?

I’m often asked by people how I figure out what aperture or other exposure setting I should use for a given shot. So I’ll walk thought that here as this is an interesting case due to complexity and power limits.

The largest factor in producing this image is depth of field. I need certain things to be in focus, like the popcorn in the upright container and the two labels that say popcorn. Since I don’t have a tilt-shift lens that would allow me to control the placement of the area of sharp focus with out stopping down I’m forced to stop down to a narrower aperture.

I don’t have to worry about shutter speed for a number of reasons. They are in no particular order, I’m shooting from a tripod, the scene is static, and the scene is completely lit by strobes. Since the strobes contribute all of their light in a very short period, I can use the highest shutter speed that allows everything to sync. In this case because I’m triggering a master flash with old style non-TTL Pocket Wizards and workout outside of the design of Canon’s wireless flash system (see note) the highest flash speed I can use is about 1/100^th of a second. Therefore, that’s my shutter speed.

For this shot I started by picking an aperture, I think it was f/16 and taking a test image. It was dark. Time to start increasing the flash powers.

I started with the dimmest and least powerful flash, the 430ex on the background. When that got to full power and I still wasn’t getting any appreciable glow on the background, it was time to start opening up the aperture. Two stops down to f/8 and we were getting there.

At this point, I was starting to open my aperture enough that I was concerned about depth of field being a problem. The only thing to do now is increase the ISO. In the case of this shot, I ended up at with ISO500 giving me the background illumination that I wanted. Camera settings ended up being 1/100^th, f/8, ISO 500.

Now for the key light; it’s simply a mater of dialing the power of the key light up or down to get the proper exposure on the foreground elements. I lucked out here, as that ended up being exactly where I had the flash set, 1/16^th power.

In the case of this shot, the aperture was limited by the performance of the lowest power flash. If I had a second 580Ex II back there, I could have stopped down a stop further due to the power difference.

a lesson in balancing dis-similarly powered flashes and being aware of the transmission factors of your gels if you’re using them.

This goes as a lesson in balancing dis-similarly powered flashes and being aware of the transmission factors of your gels if you’re using them. The key light was set four stops below full power, while the background flash was set at full power. One of those stops is accounted for in the difference between flash powers, the other three are due to the Rosco Storaro red gel that was used to color it. It’s my favorite color so far for getting a rich saturated red; unfortunately, it eats three stops of light.

Sculpting the Scene

With the lighting setup, it was time to get to the actual fun part, placing individual popcorn kernels. I knew ahead of time I wouldn’t have enough popcorn to make the whole scene I wanted form popcorn alone. So I had to add a lot of filler. In this case, the filler was printer paper.

I started by crumpling sheets of paper to fill the bottoms of the containers and form the cores of the hills of popcorn. Then I covered the tops of the hills with crumpled but smoothed out paper.

Adding Popcorn

The final step in preparation was to add and arrange the popcorn. It had cut off only a corner of the bag of popcorn so I had some control while pouring it. However, it turns out where ever I didn’t have a lot of tabletop or a paper dam installed popcorn inevitably fell off the table and went everywhere, “cleanup on isle 1”.

I shot this tethered, with Lightroom auto importing the images. The big preview with a full RAW histogram was definitely helpful in insuring I had the right exposure dialed in, as the in-camera histogram is often not quite as helpful as it would seem.

The scene was shot at 33mm, on my 1.3x crop 1D mk.3 that worked out to 43mm or just a smidge on the wider-than-normal side. I was a little surprised at this, but the tests at longer focal lengths didn’t work out nearly as well.

The remainder of the time was spent moving individual kernels around until I had no obvious holes in the field of popcorn, the right patterning in the “hills” and a properly full container.

All told, I shot about 60 frames to get everything dialed in and nailed, including some with the focus adjusted to varying positions just in case (this actually was very important).

How Things Could Have Been Easier

What could have made things easier? Well for starters, a second 580Ex for the background light, it would have given me a stop narrower aperture, so I would have been shooting at f/11 and not f/8.

Moving up a step from that would have been the jump to full studio strobes with modeling lights. With the limitations I had on shutter speed, controlling the ambient light levels was important to keeping them from influencing the scene unexpectedly. The modeling lights and flash power has two advantages. More flash power, especially for the background light, would directly translate to a narrower aperture and more depth of field. Second, the modeling lights would allow the scene to be brightly illuminated for focusing and composition and then only lit by the strobes for the actual exposure.

All in all though, I’m happy with the results given the time, conditions and equipment I had available to work with.

Final Product

It doesn’t make a difference to the light bouncing off the ceiling and it’s one less angle you have to rotate your flash though so it’s quicker.

Like this, if you rotate the grip towards the top for a vertical shot.	Or this, if you rotate the grip towards the bottom for a vertical shot.
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