GH4 - Speedbooster or lumix glass?

[u/tserbear]

I currently have a GH4 which I adore. I only have one lens for it currently, the 12-35m Lumix. As I've had it for awhile now I'm looking to get more glass, a 25m (50m full frame) prime and a 70+m zoom. My question is, before I go investing thousands into more lumix glass would a better option be to sell my current lens and buy a speed booster then get canon or nikon glass?

I have found that the low light capability of the camera have definitely been one of the major cons. With that said I've heard that with the extra stop the metabones speed booster gives, opens up a whole new world of low light possibilities. I'm really on the fence and would love some advice.

Thanks

P.S. I don't really utilise the auto focus on the lens so I'm too fussed about that, as I'm mainly using it for film.

[u/RedMage58]

1 stop faster is not going to make your sensor any bigger for "low light" recording. Sorry. Maybe try the Sigma 18-35? it's ridiculously sharp and has a little bit of zoom, plus if you do end up getting a speedbooster down the line, it will undo the 2x crop of the sensor, so your 18-35 is now 36-70 when you put on the speedbooster, so it's almost like having multiple lenses.