Wireless P-TTL flash test results

Already had asked that one for you Peter.

I think the problem might be how the P-TTL fights not to burn the highlights but you still have the flash in your frame/photo. I think that might be the problem.

I would try the following setups:

All tests with the camera in M mode, f/5.6, 1/60s, ISO400.

1. Take a test shot without any flash to see how dark the image is without flash (hopefully dark, but not absolutely pitch black. If it's really black, then increase the ISO to 800 or 1600).

2. No AF540, just pop-up flash
a. With the flash mode set to 'normal'
b. With the flash mode set to 'wireless', and the pop-up set as master
c. With the flash mode set to 'wireless', and the pop-up set as controller

3. With the AF540 mounted on the hotshoe

4. With the AF540 firing into the frame from one side at 45 degrees. Because of the sheer power of the AF540, make sure it's a couple of metres away from the subject. (I suggest you put a soft toy or something to focus on and to check for shadows).
a. With the popup flash set to master (you should see the shadows)
b. With the popup flash set to controller (you should see only the shadow from the AF540)


Do also make sure that the custom function 'Release when charging' is off (so the shutter will definitely not fire when the pop-up is still charging). Sorry, I can't remember the exact term!

Let us know a rough idea of the results

Matt

Sorry for the delay guys!

Firstly I wanted to say thank you to you all - I appreciate your feedback/comments/suggestions.

With regards to having the AF-540FGZ as the subject of the photo - I'd actually started do the original tests with a 'normal' subject and the AF540 off camera and out of the shot. But then I saw a post online where someone had taken shots of the flash - the rational being that you can see what flashes it is producing.

The same logic was applied to the next set of tests I conducted (and was also suggested by amoringello) - By shooting into a mirror we could see what the built-in flash is doing.

So here you go: http://www.adam-fogerty.com/pentax_flash_test/index.html#test2

I used the same "3 shots in each camera mode" format for each of the following setups:

With the built-in flash set to auto (i.e. not wireless)
With the built-in flash set to master
With the built-in flash set to controller
With the AF-540FGZ mounted on the hot-shoe

You can see that even with the built-in flash set to auto, it doesn't appear to have fired in a couple of frames. The only setup that provided consistant results is with the AF-540 mounted on the camera.

I will try to do another set of tests with a non-reflective subject in case that's causing a problem.

Can anyone see any pattern in this second set of results that might suggest anything meaningful?

I'm leaning towards the AF-540 being okay and there being an issue with the built-in flash...

Thanks again,

Adam

I think it is.
The P-TTL sees the flash light and don't want to over-expose that.

Agree with Stefan 1000%.

P-TTL invariably under-exposes when there are reflections.

That's why it is far better to use manual flash unless you absolutely have to use an automatic mode.

My AF flashguns will be on the market soon as I seldom use them.

G

I'd be interested in one of your AF360FGZ flashes.