Re: 540 let me down Christmas Day
I just finished shooting a dinner with a K10D and AF540 with Stofen diffuser in a hotel ballroom with high ceilings painted reddish brown and lots of glassware and sparkly things. To get ready for this I've been practicing and reading this forum for the last several weeks. While the Owner's Manual is a bit obtuse, I whole heartily agree with both the last two posters, "nosnoop" and "wlachan" on what is going on. The P-TTL system ensures you don't blow highlights and it doesn't matter what metering system you use.
I shot around 120 images of which I saved 70 and posted 38 for all to see. For about half of these I needed to increase the exposure some amount, although there was no single amount of adjustment needed. Its not like I could dial in a single exposure adjustment when I was taking the images and everything would then be correct. Luckily doing this type of adjustments is easy to do in SilkyPix.
What I liked was I started with no blown highlights so I was able to make exposure adjustments which resulted in nice looking images. I was also constantly varying the flash position from straight forward, 45 degrees, to straight up towards the ceiling to get the best combination of light. This was the most difficult lighting environment I've shot under.
In practicing before the event, I tried using both Automatic and Manual flash modes. Automatic had a tendency to slightly overexpose, and Manual is simply not suited for this type of environment. Too much variation in exposure and the action is too fast paced.
Here is an example of my most underexposed image.

When I looked at this in my LCD right after I took it, I couldn't figure out what went wrong, but the people had moved on, and so did I. I only got the one shot. It wasn't until I brought it up in SilkyPix that I noticed the reflection from the wall thermostat. There's always something. It took an extra 2.5 f-stops of exposure compensation to get it correct, along with a bit of Photoshop to get rid of the reflection.

Again, the P-TTL system is making exposure adjustments to ensure no blown highlights. When the shooting environment has lots of reflective surfaces, like glassware, sparkly table centerpieces, dresses, etc. it will give an image which is underexposed to some degree. I haven't seen any system which results in nice exposures every time under these conditions.
Overall, I like the AF540 although I agree it can be maddening at times to use. For this event the AF540 wouldn't flash at all initially until I figured out it wasn't seated in the hot flash correctly and the contacts weren't lined up. I've concluded that in most instances of odd exposures, etc. its not the fault of the AF540.
If you don't want the extra work required with a P-TTL system of preserving highlights, then use the Automatic mode and be willing to accept blown highlights in a certain percentage of your images. Again, under these conditions, I haven't found a simply answer to getting correctly exposed images all the time.
Here is the result of an image for which the P-TTL system was made for. Short distance from a person with no reflective surfaces. No exposure adjustments were required.
