I've been doing HDR for quite some time and feel very comfortable with it. Lately though, I've been running into an issue when doing HDR at night (low light) - I normally shoot daylight HDRs.
I normally bracket like this: -2, -1, 0, +1, +2 (the number of frames varies).
What I am running into is that instead of getting a +2, and a +1, I end up with TWO +1s (two frames that were taken with the same exact, exact, shutter speed - 30s in this specific case). It is like I'm bumping up against a long exposure limit or something. Is this expected? Am I just doing something wrong?