It's nice to do practical tests with your camera that help you get the most out of it. I was capturing RAW. The choice of subject matter was inspired by some of the excellent work by some of the photographers I've had the pleasure of meeting through Behance.
My goal was to see if the ISO setting affected the camera's dynamic range without modifying the in camera dynamic range setting that was fixed at 100. I thought that might be an issue and wanted to check for myself instead of reading some technical review. I took identical frames at different ISO settings ( 200 400 800 1600 3200 6400 ), helped by the camera's inbuilt neutral density filter ( seems around two stops down). In the field the only noticeable difference was that the images in review mode in the electronic viewfinder seemed less sharp as I cranked up the ISO.
Of course there was a difference in the noise but to my utter surprise I felt it remained very manageable : higher ISO are fine as long as they are well exposed.
These were all taken on the little fuji x100 during an afternoon stroll on the 2nd of September 2012 .
My conclusion: in Lightroom 3 there was no noticeable difference to my eye in the range captured unlike when using film pulling or pushing it will have massive effects. At different ISO settings for the same seem with exposure metered on the same spot, shadows, mid-tones and highlights seemed practically identical in detail with the exception of noise that can be likened to grain.
I was only interested in producing black and white images from the files.I couldn't quantify the range captured in number of f-stops and of course I did some editing to my taste but obviously the images can only show the details captured. The practical range is that of a sunny day with shadows and bright clouds.
All in all I've learned not to worry about the effect of the ISO settings on the dynamic range. The most important thing is to expose correctly.
Next step is to check the effect of the camera's dynamic range setting.