i think the best way to do this is by using the HDR method. take one pic of just the background and then one pic of you and an underexposed background then combine the two
still don't get it??
what he want is the background night scene with lights,
if expose half way than the person jump in the scene,
where the place he stand has already expose with background citylights
so he become a half transparent ghost liao.
if background no light, than why so troublesome to ask the person jump in and out.
just pop a flash shot will do.
very interesting thread on topic i have been pondering recently.
in fact i was abt to try out 1/2 sec, iso 400, f4, redeye flash.
duno whether the effect is ok.
anyway, want to try this type of shots..
best time is around 7.15pm, just right after sunset, the street lights has lighted up, and the sky is still in very nice blue, this is the time that we call "magic hour", the best time for city scape night scene.
set up tripod, use flash, pose the person, depend on the ambient light, the shutter speed is around one or two second, very easy to hold still.
hope this help.