Tuesday, October 14, 2008

Wireless P-TTL Flash with the Pentax AF360FGZ and AF540FGZ

Off-Camera Flash Is Your Friend

Above: A wireless AF360FGZ firing P-TTL without any cables or transmitters.

Strobist readers are already familiar with how useful it is to get your flash off the camera. The creativity and control that you have over your lighting is empowered the second you move your flash from sitting directly above the camera. Your light can be pointed at different angles, used for better bounces and fills in new directions, for highlights (from above) and rim lights (from behind), and even for special effects. And multiple flashes can be triggered for a lighting assault to turn boring light into atmosphere that is complimentary and brilliant. Often, it's the difference between taking a picture and making a picture, because you sculpt directly with light.

One of the misconceptions of off-camera flash is that it requires a lot of extra gear, like stands, umbrellas, clamps, slave devices, cables or transmitters. But scores of people are out there every day trying to create miracles with just bare bones equipment. And Pentax users needn't be shy of the boasting from Canon and Nikon users about their wireless flashes; we can do a lot, too.

Wireless Doesn't Have To Be Complicated

Now if there's any secret about off-camera flash, it's how easy it is to do with a basic wireless setup. Paired down to essentials, it's just your camera and one flash (maybe two for certain cameras if you want P-TTL*), no cables or transmitters or anything extra.

*P-TTL is Pentax's flash metering technology that allows the flash to make its own output adjustments based on the camera's exposure settings.

And chances are that if you own a recent Pentax flash (one of the two Auto Flash AF models marked FGZ: the AF360FGZ and the AF540FGZ) and any semi-pro Pentax DSLR (K20D, K200D, K10D, *ist D), you already have all the tools you need.

For P-TTL wireless, the other Pentax DSLR models (K100D Super, K110D, K100D, *ist DL series, *ist DS series) need to have two FGZ flashes (one FGZ mounted on your camera) to control a P-TTL flash, because the built-in flashes on these cameras are not wireless controllers and can only trigger slave "Auto" or "Manual" flash modes on an off-camera flash. If you want to ignore P-TTL, just substitute "Auto" mode for P-TTL in the example below, and you can go right ahead. It's still good.

Getting Started

Let's set up a small Halloween exercise so that you can see how easy it can be to use a single flash off-camera. I'll refer to the K10D and AF360FGZ, but it could just as easily be one of the other supported models I mentioned earlier, like the K200D or AF540FGZ.

Use a friend to be your portrait subject. The goal here is to have your friend hold the flash under their chin, like a flashlight when you tell ghost stories around the campfire, and it will go off with P-TTL (Pentax Through-The-Lens) metering for an auto-flash exposure when you take the picture (below). Your Pentax camera's built-in pop-up flash will control the exposure through a series of pre-flashes, but it will not be lighting the shot at all. This works best in a room with dim lighting that requires flash at ISO 100 or 200.

Above: Subject holding the untethered flash under her chin. Boo!

The most complicated part of the exercise is verifying that your settings are correct, but once you've done this a couple of times, it's easy to remember.

1. Pair the flash with the camera.

First, connect the FGZ flash to the hot shoe of your camera. The flash and camera need to know they're working together, and once you've paired them by matching their settings, you can use them like this again even after you've powered them both off (providing you're using the same settings).

2. Set the flash to Wireless (Slave) and P-TTL mode, and verify that it's set as Channel 1 and Slave 1.

Above: Settings for P-TTL Wireless flash on the AF360FGZ while connected to the camera.

Turn the Power switch on the flash to the middle position: Wireless. Next, set the Wireless setting (M-C-S) slider switch to S, for Slave. Finally, press the Mode button to set the flash mode to P-TTL. Easy enough, right?

Now if this is the first time you've done wireless, you'll need to do some verifications of embedded settings found on the LCD. Make sure your flash is set to Channel 1 by sliding the Setting switch. The channel number will then display itself on the LCD. Slide the Settting switch back when you're done. Next, check that the flash is set as Slave 1 (instruction pictured below). Warning: If your flash is set as Slave 2, and it sometimes defaults that way on its own, the flash won't fire in P-TTL mode. You may want to consult your manual to learn more about those settings.

Above: holding down the Light button for 2 seconds reveals the setting that this flash is set to Slave 1.

3. Set the camera to Wireless flash and verify Controller flash firing is de-activated.

Above: Function menu setting for Wireless Mode on the K10D/K20D.

In the function menu, set the flash setting to Wireless. This let's the camera know that it will be communicating in pre-flashes with a wireless flash.

For P-TTL, you'll now check your camera's menu settings so that the camera will not fire the built-in flash while it acts as in Wireless mode. A controller flash firing is useful if you want the built-in flash to act as a fill flash (with maybe -1.5 EV). But because we only want the external flash showing up in the photo, you must set the option as "Off" instead to keep the built-in flash from firing while the shutter is open. 

Above: The Advanced Menu setting to make the on-board flash "controller-off", so that it won't act as fill flash (master or slave).

4. Depress the shutter trigger half-way to have the camera and flash confirm all the settings to each other.

With a half-press, the flash should emit some test flashes for focus, and then you'll know the body and flash have communicated their settings successfully.

5. Take the flash off the camera body and pop-up the camera's built-in flash.

You can now hand the flash over to your friend to point up at their face. Just slide it off the hot shoe (it's okay that the power is still on) and let your friend hold it under their chin. Remember to pop-up the built-in flash on the camera so that it will be able to communicate with the wireless flash through the series of pre-flashes (non P-TTL users, this is when you attach your second FGZ flash to the hotshoe and set its mode to Wireless and Controller). Try not to block the controller flash: it should have a direct line of sight to the wireless flash's sensor.

6. Go ahead, take the picture!

Try using the Program mode on your camera, so that the auto exposure will choose an appropriate flash-sync speed around 1/60 sec and control the aperture. When you take the shot, the built-in flash on the camera will pulse a quick strobe and then the shutter and wireless flash will go off. The result should be a high-contrast shot, with just the face lit up by the external flash (as pictured up above).

With the first shot finished, now try having your friend point the flash from different directions, or try holding the flash yourself in your free hand, pointing it at walls for bounce or at your subject with indirect angles. By learning to hand hold the flash with your free hand, you can get more variety in bounce direction than you can with the flash mounted on the camera.

As Obi Wan said, "You have taken your first step into a larger world."

All photos © OK1000 Pentax Blog, 2008.


Victor Lam said...

Hello, Thanks for writing the step by step. I have one question tho for wireless flash, I am using K10D, and if I use some of the K, M lens I notice that I can't choose Wireless flash, but is there anyway to do it? or I have to use extension cable?


Matthew Miller said...

Victor — no luck. P-TTL doesn't work with K and M lenses, so wireless P-TTL can't either.

Lars K. Christensen said...

Very nice and clear explanation - much more logical than the manuals ;-)

Anonymous said...

Step 3.5 screen shot but no instructions. should be to press camera Menu button, scroll left to C, then scroll up (from bottom) 2x to get to the wireless flash setting.

Chris Beeson said...

I believe the first operating system for the K10D couldn't use the built-in flash as a wireless controller, and you would need a firmware upgrade to get this functionality. That's a simple operation - must be, I managed it - and details are on Pentax's support site.

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