I had actually intended to post another image today, but chose to post-process and upload this one instead, following a great question I received on Twitter today.  The, in short:  When shooting HDR brackets in low light environments, would I rather open the aperture more, or would I rather increase the ISO, if trying to maintain reasonable shutter speeds (read: 30 seconds or faster)? Answer: I’d be far more inclined to open that aperture more. Take today’s photo for example; by the time I shot this, the sun was already down.  So I turned to my trusty Nikkor 50mm f/1.4, dropped my ISO to L1.0 (Nikon speak for ISO 100), set my aperture to f/2.0 (only because I wanted just a wee bit more depth of field than the wide-open setting of f/1.4 would give me, and bracketed away.  I ended up with the fastest exposure being 1/125 sec and the slowest 1/30 sec.  Not bad, and I was off to shoot my next set elsewhere without having to wait several minutes for the bracketing to completer, had I dialed in f/11 or f/16.  The above said, everything also depends on the importance of what you’ve got goin’ on in the background.  In this photograph, the background was not as important as the subject, and I lost nothing by letting it blur out with the larger aperture.  Had I been shooting a scene where I also wanted the background objects to be crisp and clear, I would have closed her down to f/5.6 or f/8 (and raised the ISO to 200) and fired away, and still been done with the brackets in a reasonable time.  Bottom line, for me at least, is I’d rather open the aperture up more, and lose depth of field, than increase the ISO, because I prefer really clean (relatively noise free) RAW brackets to work with when shooting HDR.  Your results may vary! (NOTE: Yes I do shoot the Nikon D700, and yes it handles noise really, really well, but I still choose to shoot my HDR brackets at ISOs no higher than 200 because I don’t like how Photomatix increases noise significantly when working with brackets with high ISOs)..