I have been bracketing my individual pano shots with my new Sigma 8mm f/3.5
lens on my Nikon D300.
I bracket either 3x (-1, 0 and +1) or 5x (-2. -1, 0, +1 and +2) but I have
been surprised to find that I nearly always have to choose the lowest
exposure from the groups of three, and sometimes even from the groups of
five. That's one or even two stops below the "normal" exposure, which has
blown highlight in almost every case.
This suggests I am consistently overexposing my shots. I tried the exposure
offset control to reduce exposures by one full stop, and this gives me a
better balance of exposures.
Then it struck me. I only notice this bias with the new Sigma lens. Could
it be that the averaging light-meter setting I use is averaging in all the
dark areas around the outside of the image circle? and perhaps resulting
in a higher exposure setting than is really necessary?
Of course I will try switching over to center-weighted metering (with a
rather large and diffuse center not a narrow "spot") on my next photo
outing, but I wondered if anybody else has experienced this?