Wireless P-TTL flash test results

I'd be greatful if you could take a look at my wireless P-TTL test results here:

http://www.adam-fogerty.com/pentax_flash_test/index.html

I suspect I have dud equipment (either the body or the flash), but I'm looking to get some confirmation.

As an example of my testing, here are three consecutive pictures taken with my K10D in aperture priority mode with the built-in flash set to wireless "master":










I changed NOTHING between shots - all I did was allow enough time for the flashes to recycle.

As you can see each image is very different in terms of which flashes are firing. Regardless of what the "correct" exposure might be, I would expect to see the SAME exposure each time.

Again there are more details of my testing methodology and photos here:

http://www.adam-fogerty.com/pentax_flash_test/index.html

Thanks in advance,

Adam

Adam,
Looks like you have the AF540 set to "SL 2" (i.e. dumb slave flash). Looks like it's picking up the pre-flash and triggering.

Double check that the Slave setting is on "SL 1" (see p54 of the manual)

If that's all set ok, then I would suggest trying another flash gun

Matt

Definately set to "slave 1" - I checked, double checked and triple checked all the settings lol.

If I owned another camera brand I'm sure it would be pretty easy finding another flash gun to borrow - either from a user or from a store - as it is I'm sure I'll have quite a hunt on my hands

Thanks again,

Adam

It might help if you updated your profile to show where you are
There's usually someone nearby who can help!
Matt

Pot, kettle, black

You said you had set the build-in flash as master and that one failed a lot of times, so I suspect it's the camera that's doing something wrong.
I see you've updated it to the new firmware, did you also had this problem with the old firmware?
And what does the build-in flash do alone without wireless?

No, its Matt the helpful flash expert, calling the kettle black.

Interesting test with even more interesting results, and not what I would expect.

From your test results I can identify two separate issues that are probably both caused by a faulty onboard flash.

1: Sometimes the onboard flash doesn't fire at all, and
2: Sometimes when the onboard flash does fire, it fails to trigger the slave flash.

The EXIF data for the 'black' frames shows that the camera thinks that the flash did fire, in compulsory flash mode, whatever that means.

Can you say whether the flash did actually fire, but maybe much lower power?

If it didn't fire, I'd suggest your camera is faulty.

Thanks for your input guys.

Matt, location updated, as requested I was born and raised in the UK, but moved out to the US for good in February of this year. Anyway, I digress...

Anvh, although the three shots I posted here were with the built-in flash set as "master", I also went through the same process with it set as "controller" and got similar results (if you consider 'completely random' the same as 'similar').

Those photos, along with a shot of the built-in flash firing on its own (not in wireless mode) are posted on my web site which I linked to in the first post. The built-in flash on its own seems to work okay - it fires consistantly.

I did originally suspect the firmware update of causing these flash issues, but on reflection perhaps I was being a bit hasty - It could be sheer coinsidence that I started trying to use wireless P-TTL again shortly after the firmware upgrade. In the past I have had the occasional black frame/mis-fire when using wireless P-TTL, but always put it down to a quirk of using wireless P-TTL that I'd have to live with.

Peter, I thought I was going to go blind watching for the flashes while doing these tests

Obviously it was pretty hard to distinguish between the pre-flash and the main flash as they are so close together, but I can say that the built-in flash was firing SOMETHING every single time. Whether it was firing everything it was supposed to is another question. The 540 seemed much more random - sometimes it output a very large burst, others a tiny burst and sometimes nothing at all. What's strange is that in the aperture priority examples I posted above, in the first frame there is no evidence of the 540 firing in the frame, but in the third shot you can clearly see that the 540 fired. The metering for the frame shouldn't have changed between the shots, so my conclusion is that it's a communication/timing issue with the flashes? Is that fair?

Thanks again,

Adam

I wonder if the completely dark room has something to do with it, just a hunch though?

btw what metering mode did you use?

The room wasn't completely dark - I'd call it 'dim'. I could see everything in the room fine with my own eyes, but there was certainly no direct sunlight.

The camera was set to multi-segment metering.

Thanks,

Adam

Just wonderin'... when you say the built-in flash is set to "master" are you expecting it to be part of the exposure or not? As Master, the built in flash should illuminate the scene regardless of the remote flash firing. You should not get a black frame. It seems to point to a problem with the built in flash.


A couple of odd ball Suggestions:
Set up a mirror in front of the camera to get the built in flash reflecting in frame.
If the built-in flash is firing as master you should get a large bright flash from the built-in flash.
If the built-in flash is firing as controller, you should get a dim flash reflecting back.


Set aperture and shutter speed to get some ambient light regardless of flash. (i.e. Are you sure the shutter is opening?) OK I'm sure this would be obvious without the flash, but hey...


What is the shutter speed set to?
If you try manual or TV mode with shutter speed set to 1" just for grins, does the behavior change? (assuming 1" doesn't completely blow out the image on its own, of course)


About two years ago I had my K10D in for repairs because it was not consistently firing the flash.
Sadly, just had my K7 camera in for repairs. Hotshoe stopped working and exposure for same scene ranged from 1/3200s to 1/25s.
Many years ago, had my istD in for repairs with issues with the flash.

I don't know anyone else with such repeated problems, but just saying it could be a bad camera.

Just looking at the images a second time... I notice a fine slight line of flash reflecting in the back of the 540's body. It appears your built-in flash is functioning.

In my opinion, PTTL utterly fails completely when there is any specular highlight in the frame.
Neither flash may be requested to give significant power to light the scene because the Pentax camera reduces flash power until specular highlights are properly exposed (which almost by definition should not be). To that end, PTTL will usually set output power to the absolute minimum. Depending on your aperture, this may not be enough to expose any of your scene.

Try moving the flash out of the frame or cover any specular areas with non-reflective material.

I would expect to see something on the carpet form the 540 being fired, but I've had similar results of nearly black frames with the slightest specular highlights. The K7 seems better, but it still suffers from this behavioral limitation.

Still, I would expect *consistent* results, which you are certainly not getting.

Try it with centre weighted or spot metering, with multi-segment it can change metering per shot, at least that would increase the consistency of the flash power a bit.

I also think the flashgun in the photo is a problem, could you maybe make a photo of a subject with the flash to the side and not in the frame?

If you want to know if it's a sync problem or not simply set the flash to manual and see what it does then.

That being the case, have you tried a similar experiment with the 540 mounted on the camera and set the 540 to wireless master?

That would help confirm/eliminate issues with some of the flash circuitry. If that all works, the issue will be with the onboard flash.

If, in your earlier experiment, the flash was firing every time, it clearly wasn't pushing out enough light sometimes. Does the onboard flash work consistently when NOT set to wireless mode?

You should mount the flash on the camera at least once anyway, and power up the camera and flash to synchronize the flash/camera wireless channels. Perhaps try changing the channel to see if things improve.