Panasonic lumix g x vario 12-35mm lens for GH3

[Dinozorr]

Hi all, I think I'm posting this I'm the right place?
But my question is I currently use aPanasonic gh3 with the kit lens14-140, I'm looking or should I say my local camera shop have offered me a very good condition panny 12-35 f2.8 lens for a great price. Is it worth the layout for this lens. I'm into astro photography so will this give me more photons?? and a slightly wider view for photographing the milkyway/landscape photography.... Plus general photography too!! They've let me borrow the lens for the weekend and I must say it seems sharp and very quick to focus... The one thing I have found which seems strange is the view on the rear screen of the gh3 seems to have a very small amount of wobble/flicker when the lens catches false light from light bulbs etc.although in normal light it's spot on. I also like its ability to focus at around 25cm.
Any thoughts and advice?
Thanks in advance, Jason

 

[laser8]

what you get is 2 mm at the wide end (more time to keep the shutter open) and about a stop of aperture, so yes it would be better than the 14-140. I like the lens very much, but I suppose for astro you'd be better served by an oly 12 f2 or some manual lens+speedbooster?