Portrait Lens advice

Next week we are having a portrait session at our local camera club. We will be using a studio lighting set-up and i'll be using my GX20, from the list of my lenses shown below what would be the best to use?
I was thinking the 50mm A F1.7 or 24-70mm FA F4, am I thinking on the right lines? This will be my first portrait session so any advice would be much appreciated.

An 'ideal' portrait lens for film would be about 85-100mm. The closest you have to producing the same field of view would be the 50mm 1:1.7 (75mm equiv) and the FA-28-70mm zoom. The 16-45mm + 1.7 T/C might give interesting results too.

There is much more to a lens than it's focal length to qualify it as a 'good portrait' lens though. If it's a bit soft wide open, more common with fast lenses, that's good too.

Ideally you want a lens with a wide aperture (to seperate the subject from any background distractions) and a medium-telephoto length. From your list I'd say the best bets would be the A50/1.7, DFA100 Macro and Sigma 70-200/2.8. No harm in taking the 28-70 as a back up though...

I'm with hefty.
the drawback to the zooms is gonna be variable apertures as you zoom, constant aperture zooms are best...
but the 50 and 100 macro (the 50 with 1.7 teleconverter would work nicely...) are your best bets..
the 16-45 may be useful if the space is cramped....
the next problem you may encounter is the studio lights may be too powerful to use properly with wide open apertures, so an nd filter or two (polarizer and or nd filters) will help there....

I've got a big camera bag so I think I'll take all you've mentioned and hope I have enough time to experiment, might take the K10D also to save on lens swaps.
Thanks for the advice chaps hopefully I get some shots good enough to let you have a look at.

The problem with camera club sessions is that it's impracticable to experiment with different light outputs and positions. Next time see if you can get the model for an hour on a one-to-one basis before or after the main shoot.

G

I use my MKI Sigma 70-200mm f2.8 quite often for portraits.