I currently have the 12-35mm and 35-100mm and would like to purchase a lens for very low light situations. There are numerous micro 4/3 lenses available such as the Panasonic/Leica 25mm and 20mm as well as many options from Voightlander, SLR Magic & Olympus. Then there is the option of one of the Metabones Speedboosters for the Micro 4/3 system. I was wondering what direction others went in for low light work. Does anyone work with one of these speedboosters on a regular basis and if so with what lenses? I know there are limitations with Autofocus but if you are willing to work in manual, it does sound very tempting to me.

The speedbooster does give you that extra sensitivity which would be very useful on f2;8 lenses, not sure if you allready have a f1.4 lens (which should give you a f1.0 something one a speedbooster) is going to help you much when it will be even harder to get your focus right.

Currently the low light sensitivity of the gh3 has been sufficient for my use, I have a 12mm f2.0, 25 f1.4, 75 f1.8 and the 12-35 f2.8 which got me through the last weddings I did.

Hi Noa, no doubt the 25mm was important for you in very poor light. I only have the two zoom lenses at the moment and am looking for just one to go with it. We can't use the metabones with the Panasonic 12-35 can we? I assume for flange reasons it is only designed to accommodate lenses designed for a larger sensors with the increased flange focal distance.

I think it won't work as you"ll loose autofocus and stabilization, you probably need full manual lenses with the speedbooster.

Isn't the Metabones an adapter for larger 35mm lenses that refocuses the image area down to the smaller 4/3 sensor which is why you get a light boost? If they work on 4/3 lenses that would be great.

That is my understanding too William, would love to know if anyone out there has any experience with using one. Otherwise will probably just go with the 20mm 1.7 from Panasonic, it is cheap and I prefer the wider scope it gives me over the 25mm, although I am sure that is great too.

The 12mm f2.0 lens from Olympus which I have is a great one for wide angle work, I use it constantly on my g6 when that one is on the steadicam.

I've got the same one Noa and it is excellent. If you are shooting F2 with 400 or 800 ISO you are getting lots of clear detail in a pretty dark environment. Once you start getting down to the 1.4's and 1.2's your very shallow DOF can be restrictive unless you're after a particular look.
The Olympus also has a nice little manual focus sleeve so you can switch between manual and auto focus by moving the sleeve rather than use the camera control. In low light it's really handy.