Originally posted by and I just tried pttl again. using M mode, pressing the green button to have the camera set the exposure yields a fairly accurate exposure. Then I changed the shutter to 1/160 and turned the flash on, bouncing it into the ceiling. I had to put +1 on the flash and +1 in the camera flash comp to get a similar exposure.
That makes no sense what you did btw?
So you set a proper exposure, then dialed the shutter to 160th and got a different result? Makes sense to me....
First off shooting bounce at 160th is silly because your flash power is halved in most cases so you need to lower the shutter to 1/60th to allow more ambient and to catch the fall off of the flash. Also what was your ISO because if it was at 100 again the flash may not be powerful enough to compensate for a bounce. You're using settings that push the PTTL to improper exposure, if you learn flash from the old school methods you'd understand why the PTTL in your case was not accurate.
Also what was the distance of the object you were exposing for, was it right in front of you or 10+ feet away because that would also determine what your bounce angle has to be. I hope you didn't bounce straight up because that has an effective range of only 5-7ft due to light fall off.