Smoke effects

A very interesting experiment by Michel Rohan, a French photographer. This picture is his. An article describes the method and the setup to generate this kind of image. See the photography wiki here: http://www.techniphoto.com/wiki/index.php?title=Smoke_pictures

BW processing

VA3_0239, originally uploaded by gugs.

I tried a strange processing on this one, playing with the different color channels, to get more details in the sky, but resulting in a strange "negative" effect in some places. I like the result, but this is of course a matter of taste. This shot has been taken in the center of Brussels, with a Nikkor 24-70 2.8 lens on a Nikon D3 camera, for what it's worth.
Any comments or suggestions welcome.

High ISO

VA3_7757, originally uploaded by gugs.

This is a bit of a crazy picture: this has been taken in the dark, with a ridiculously long lens (200-400VR) on a D3 at ISO 6400, with a very slow shutter speed. The wrong configuration at the wrong place... but the result is in fact what I wanted.