Occasional darker frames when using ML bulb ramping

Last night I setup my camera to catch the sunset on the mountains behind our house. I'm using a T2i and 70-200 f4L. I set everything up in M, even the WB. I then enabled the intervalometer in ML and decided to play around with bulb ramping for the first time.

When I assembled the time lapse in after effects I noticed there were some frames that were a darker exposure than the others. Anyone ever experience this?

How many frames were dark,individual frames at a time, or sets of frames? I've found that using bulb ramping can bump the ISO pretty quickly, sometimes causing flicker to the point that it's too much work to correct. But, if it's only a few frames, try LR timelapse to build a nice curve and deflicker.

I'm still very much a time lapse n00b, but setting for longish exposures and then manually bumping the ISO two times or so has worked well, and can be deflickered with LR timelapse. I've also had to trash a few time lapse sets from setting the intervalometer at too low of a time, my T2i sensor gets a little upset when it gets hot, creating it's own special kind of flicker!

Hope any of the above rambling helps!

Interesting. I haven't tried the ramping facility yet as I was a little sceptical.

While not an ideal solution I have found duplicating the footage on two parallel time lines means you can lighten one line and blend them as the frames get darker. Not ideal but does extend the usable length of the footage as it gets darker.