Good news! Canon just released a firmware update for the 5D Mark II, and it looks like the black dots problem is fixed. Before installing the new firmware, I setup my camera and a test subject and took a series of images. Then I installed the new 1.0.7 firmware without moving the camera and reshot the same images. You can see the comparisons below.
(The swatches are bigger than in the original test from a few weeks ago, because apparently I had my camera closer to the subject this time. I didn’t notice until afterwards, and there’s no way to rollback the firmware and reshoot.)
|Original (1.0.6) firmware||New (1.0.7) firmware|
So it looks like everything is okay. Hopefully people who photograph city lights and other problematic subjects will confirm my findings with real-world images.
Update: Just a word of caution…I normally wait a little while before installing new software, just in case the update actually introduces new problems. This time I rushed in so that I could serve as a guinea pig. Things seem to be fine so far, but if you aren’t bedeviled by black dots you might want to wait a week or two and see what happens.