In answering this post by Nicola90s microSD and time to record pictures I discovered a feature of AEB bracketing which many of us probably don't realise; the fixed parameter used in exposure bracketing depends upon the exposure time:

- Under normal lighting conditions, the ISO value is held fixed while the exposure time is varied in alternate 0.7 IL steps: as an example a series shot at 100 ISO would be 1) 1/40 sec, 2) 1/60 sec, 3) 1/25 sec, 4) 1/100 sec, and 5) 1/15 sec.

- However, under long exposure conditions (night flying), the exposure time is fixed, while the ISO values are varied in alternate 0.7 IL steps. As an example for 1 sec exposure: 1) 200 ISO, 2) 123 ISO, 3) 324 ISO, 4) 81 ISO, and 5) 492 ISO.

I hope that this is useful to others doing HDR photos using the AEB mode.
Have fun & good flying!

This would be in auto mode, because the camera has a set programme of exposure settings to choose from to get the best theoretical results.

I've just tested it in manual mode & it does the same, which is lame.  It doesn't matter which parameter you have the wheel set to adjust, it always adjusts ISO when shutter speeds get long.  It even reduces ISO to less than 100, which is unavailable as a manual adjustment.  It's like you can have manual control, but not really.

nigelw Posted at 2016-4-30 14:23
This would be in auto mode, because the camera has a set programme of exposure settings to choose fr ...

Yes, I was testing in manual mode when I discovered this feature (personally never use auto mode). I think it is good to keep this in mind when shooting slow. It's a design choice, but the noise results will not be great. Yes, in my long exposure example shot (above) the ISO went below 100.

johnsr Posted at 2016-4-30 16:10
Yes, I was testing in manual mode when I discovered this feature (personally never use auto mode).  ...

It's definitely good to know.  Nothing worse than a camera that doesn't do what you expect.  It's a pain, but at least we know to bracket manually in such situations.  Well spotted by the way.