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12-23-2011, 09:37 PM   #1
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Confusing Wireless P-TTL Documentation

I've been trying to get wireless P-TTL working with my K-5 and Metz 58-AF2 flash. When it works, it seems to work fine. But getting it to work is frustrating, and the documentation provided by Pentax and Metz just add more confusion.

For example, the Pentax K-5 manual states on page 190:
QuoteQuote:
When set to "W" mode, the channel currently set for the built-in flash is displayed in the viewfinder for 10 seconds.
And on page 191:
QuoteQuote:
The channel for the built-in flash is displayed in the viewfinder and on the LCD panel. The factory default setting is CH1.
However neither of those thing appear to be true on my K-5. It never displays the channel of the built-in flash. It just shows me the wireless flash symbol. The Metz documentation is an overall non-amusing joke.

I've tried following the procedure for setting up wireless P-TTL as outlined in the K-5 manual, and it fails consistently. When I try it, I get the exact same flash output regardless of exposure compensation or flash adjustment made on the camera. ONCE, I got it to work by accident, and it was great. Flash output was strong, exposure was consistent, and changing exposure compensation on the camera resulted in a stronger or weaker flash, as expected. But since then, I've been unable to replicate this success.

Is there some kind of different procedure to follow on the Metz 58 AF-2 to get wireless P-TTL to work on the K-5? I'm getting really aggravated.

12-24-2011, 03:53 PM - 3 Likes   #2
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You may already be doing this, but just in case...

Step 1) Mount the flash on the hotshoe of the camera. Turn the flash on, then turn the camera on.

Step 2) Hit the "Fn" button and go into the flash menu. Select wireless mode (the lightning bolt with the W) You'll notice in top LCD screen on your camera that "CH 1" is displayed. You can change it to 1-4, but the only reason to do so would be if you're shooting an event with another photographer, pTTL does not support individual flash zones. Press the shutter button half way to activate the meter. You should notice on the back of your flash that "pTTL" is now displayed instead of "TTL".

Step 3) Remove the flash from your camera. Hit "sel" and arrow down until you get to "remote", hit the enter button and then arrow down again until it says "slave". Now position your flash in the room. On the left side of the flash (if you're looking at the back display panel) about two inches above the USB port is a tiny IR sensor, that is the optical slave. However you aim the flash head, make sure that sensor has a clear line of sight to the camera.

Step 4) Pop up your on-camera flash, or mount a second flash on the hotshoe, and you're ready to shoot. You can dial in anywhere from +1EV to -2EV flash compensation from the camera's flash menu. By default the on-board flash will contribute to the exposure, if you don't want it to do so, look for an option called "flash in wireless mode" in your camera's custom menu and set it to "off" (it's #29 on the K20d, but might be different on the K5)

I know it sounds like a lot, but practice a few times and it becomes second nature.

Note that you can also adjust EV compensation on the flash itself and it has a cumulative effect with any you dial in on the camera (so +1 on the flash and +1 on the camera yields +2). This is useful for multi-light setups, say if you want your fill light to be one stop less than your main, you can select -1 on your flash unit providing the fill, set your main unit at 0, and adjust both in parallel from the camera's flash menu.

Let us know how it works, and feel free to "like" this post if it was helpful
12-24-2011, 09:12 PM   #3
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Thanks for that write-up.

That procedure is somewhat different from the one in the manual. I finally got to see the Channel indication displayed on the camera, for once. However wireless P-TTL is disappointing. I get very inconsistent results, usually on the dark side, with almost no flash intensity control from the camera.

On the other hand, setting the Metz 58-AF2 to Auto and using it wirelessly (in the exact same way) works flawlessly. Flash intensity is controlled precisely using the camera's exposure compensation (not flash EV comp, but the actual EV comp that I adjust using the +/- button), and the results are very predictable. In this mode, the flash is using its own meter to determine how bright the scene needs to be rather than just blindly doing what P-TTL tells it to. If the camra wants +5 EV, then the flash over-exposes by +5 EV.

I think I'll stick to P-TTL for on-camera use and Auto or Manual for off-camera.
12-24-2011, 10:10 PM   #4
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Agreed, manual flash is my mode of choice because from shot to shot it's always the same, and therefore easy to fix in post if it's a little off (doesn't hurt that I have a fancy light meter). I do love Auto mode though, especially when the flash is off camera, you can lie to it about your aperture, and it'll believe you. I guess that's what EV compensation is for, but that's how I'm used to doing it on my old 45CL-4. You still need to make sure your subject is in the center 25° of the flash's sensor's field of view, and fairly large in the frame. Auto doesn't work very will if your subject is a long distance from the flash.

pTTL is best reserved for occasions when you don't have time to make exposure decisions in my opinion. Here's a tip that may improve your consistency though, don't meter then recompose as you might in normal ambient conditions, instead, compose, then select the AF point that is closest to your subject. pTTL will try to expose for whatever is at the AF point at the time the shutter is fully pressed, not when the meter was activated.

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