420EX Exposure Comp in Manual Mode

[turbines]

When shooting indoors with bright outdoor backlighting with my G3/420 I have found the following. When I use the Program Mode with Evaluative metering, Exposure comp at -2 and Flash Comp at +2/3. This leaves the background scene about 1 stop overexposed and the flashlit subject in the forground about. I assume this is because the exposure and AF bracket is biased toward the darker subject in the foreground.

I ran some tests and found that if I shoot a similar scene using a manual standard ISO 50 exposure of 1/250 @ f8 the background is well exposed. If that manual exposure is combined with the 420 on full at a GN of 48 with a Stofen Omni-Bounce I get excellent results. This GN would indicate that the correct distance at f8 would be about 6 feet. I have noticed however that moving somewhat beyond that distance still yields correct exposures and in thoses cases the camera exposure data shows that the flash is providing + compensation up to 2 full stops.

Have I missed somethiing in the manual or does the 420EX GN have some reserve power even in the manual full flash mode? Surely not 2 stops!

[turbines]

Ooops! Too many numbers in my notes. I meant GN 25 at ISO 50 and and f8 distance of 3 feet. If I then move further to 6 feet I still get good forground exposure but it shows a +2 flash comp.