Thanks Wojtek!

I've started HDR last year after the ISU congress and discussing with David Kesner.
He's using a single DSLR on a slide bar and tripod. Using two cameras is much easier but I restricted myself to static scenes only, much like when doing cha-cha.
Then I've tested the anti-ghosting feature of Photomatix Pro and it's really doing wonders on moving elements in the pictures.
I don't know how it does it but it manages to detect and fuse moving elements most of the time automatically.
You also have a manual mode where you circle with the mouse the moving elements that have not been processed correctly.
See for instance :
http://www.stereoscopie.fr/php/images.php?img=Montmartre_244
With the wide-angle lenses I've also started taking HDR handheld without tripod!

What Canon lens did you use and with what adapter? 

I've bought two used Canon FD lenses (the old ones with the large silver locking ring).
I've first bought 100mm but they are way too long and of very limited usage for me.
The 50mm is a good option. They are not light as they are not the standard 50mm lenses that fitted SLR at the time but the 3.5 macro version with a detachable extender for closer focusing.
See:
http://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/fdmacro/50macro.htm

For the mounting the lenses on the GX1, I've selected these adapters on eBay:
http://www.ebay.com/itm/Canon-FD-Lens-to-Micro-4-3-M4-3-adapter-with-1-4-Tripod-Mount-E-PL3-PL1-GF3-GF2-/230722379347
Because it has its own (removable if needed) tripod mount that you will use instead of the camera's when using these old and heavy lenses.
Of course you are in full manual mode (aperture, focus) and I regularly forget to turn the ring on the adapter to close the diaphragm!

I?ve just tested Panasonic lens Lumix G Vario 14-140mm F3.5-5.6 ASPH Power O.I.S. and it appeared surprisingly good

Good to know!
I've also a pair of Panasonic 14mm pancake lenses and I'm looking at the new 12-32 zoom.

Pierre.