Here are some test shots that I made this evening in my living room with the blinds closed and the light off. Just enough light to autofocus. Attempting to show how the flash interacts with various exposure modes.
I used a convenient (and serene) model with the following setup:
- K-5
- DA* 16-50mm at 50mm
- AF-360FGZ flash with a Sto-Fen Omnibounce
- Flash exposure compensation of -0.3 EV (for taste)
I use the Omnibounce because I like the even illumination that it produces (much better than just pointing the flash at the ceiling), even though it reduces the effective guide number. If you've not used one, it
only works indoors: outside there are generally no surfaces to bounce off.
For reference, here's a shot without flash: F5.6, 1/25, ISO 12800.
On hindsight, I should have dialled in some positive exposure compensation, because my subject was bright - so many things to remember!
Started off in manual mode and went round the dial.
Manual mode: F5.6, 1/80, ISO 100.
TAv: F5.6, 1/80, ISO 25600!
Av: F5.6, 1/100, ISO 100.
Tv: F2.8, 1/80, IS0 100.
Sv: F2.8, 1/100, ISO 100.
Observations. By and large, P-TTL is doing its job admirably. All but one are decently exposed. TAv was an absolute disaster because ISO is set automatically to expose without flash and you can't change it. It's a good mode for outdoors, but not so good indoors and rotten for flash photography. The modes where you can't control the shutter speed have the shutter set to 1/100. In actual fact, the shutter speed is set according to lens focal length - at 24mm I'd get 1/50. The modes where you can't control aperture have aperture set to wide open and you can't change this. In case you're interested, green mode didn't look so hot (F7.1, 1/100, ISO 3200), but it was a lot better than TAv. Anyway, we don't use green mode round here, do we? We can conclude that manual mode is the best because it is the only one that gives you control over all shooting parameters.
Now for HSS.
There is definitely an issue using this in Tv mode on the K-5. When you attempt to dial shutter speeds faster than 1/180, the camera stops for a few seconds before setting the shutter speed. This horrible input lag means that you can't really control the shutter speed - you'll just end up with something slightly random; turning the front control dial sets you back to 1/180. Manual mode has no such problem - yet another good reason to use manual with flash.
When using high speed sync, the flash has a shorter duration, which has quite an effect on the guide number. The 360 has a guide number of 30 at the 50mm length I was using. Engage HSS and this drops to 13.4 at 1/250. I don't know whether it's a limitation of the K-5 or P-TTL (I suspect the latter) but there is no automatic compensation for this loss of light. The way to increase the effective guide number is to bump up the ISO. Here are a couple of sample shots, both in manual mode:
F4, 1/500, ISO 800.
F4, 1/1000, ISO 1600.
These are actually pretty good. Being able to get 1/1000 indoors at a perfectly usable ISO 1600 is simply amazing. And the 360 costs a
lot less than an F1.2 lens! The exposures are a bit brighter than the earlier ones, but that's because I didn't calculate the exposure, simply made an educated guess. It's good enough, particularly since I could have tweaked the exposure in post had I so desired.
I hope people find this useful and I also hope that I've shown that there are no fundamental issues with using P-TTL flash. So long as you're aware of a couple of quirks, such as the interaction with different shooting modes and the issues with HSS, you should get pleasing results first time, every time. And I highly recommend the Sto-Fen.
People with blown-out photographs, please post examples with details of settings and the lens used and let's see whether we can diagnose your issues.