That starts at 24 and stretches to 120mm or more?
I've wondered about that...
Panasonic makes a Micro Four Thirds 12-60mm (=24-120mm) f/3.5-5.6. It's a wonderful all-around lens. Later Panasonic with Leica branding released a f/2.8-4 version. It was expensive, and I had no need for f/2.8 so I passed on it.
I appreciate the wider 24mm (vs 28mm), and 120mm is a nice reach.
I can understand why you would want this focal length for Sony.
(Would I? I'm not sure... I use mostly primes on my Sony. )
That sums up the issue. That Panasonic lens has very good performance and weighs 210gm. A Sony equivalent is over 3X the weight. If you travel, primes on Sony are the way to go. The zooms get big real quick.
But if you are happy to travel with the 12-60mm/3.5-5.6 as your single lens, the question is why don't you downsize much more significantly to a 1" compact, like the Sony RX100VII (24-200mm eq., F2.8-4.5, 302g) or Canon G5XII (24-120mm eq, F1.8-2.8, 340g)? The smaller sensor is more than compensated by a brighter lens, while the weight is literally halved, compared to say a GX9 + 12-60mm.
However, let's say you want to treat your M43 camera as a system camera and the 12-60mm is just one lens in a system supposed to perform all round. For example, beyond having this zoom lens with a convenient range, you also want some low light capability, some potential for background blur and some UWA perspective as well. On FF E-mount, you can do it using two lenses, e.g. this is close to what I currently use:
Sony A7C.....509g
Tamron 28-200mm/2.8-5.6....575g
Sony 16-35mm/4 G....353g
........................................................................
Total 1437g (
Compact Camera Meter (camerasize.com))
Let's try to put a somewhat comparable system around the GX9+12-60mm:
Panasonic GX9.....450g
Panasonic 12-60mm/3.5-5.6....210g
Panasonic 8-18mm/2.8-4.......315g
Panasonic 12mm/1.4.....335g
Panasonic 25mm/1.7......125g
............................................................................
Total 1435g (
Compact Camera Meter (camerasize.com))
So you need many more lenses and you are not nearly replicating the capability of the FF system, like missing a portrait prime, for example. I also assumed that 120mm eq is long enough for you, but clearly, replicating the reach of the FF system needs another lens, like the Panasonic 35-100mm/2.8, or throwing out that 12-60mm in lieu of something longer, like the Olympus 12-100mm/4, which then is as large as the Tamron. You can play with this, choose some smaller, while less capable lenses, but at the end of the day, you always end up juggling with many lenses to poorly replicate what FF can do with just two midrange zooms.
Even if you cut down the M43 system to just a minimalist version with a single small prime (say GX9+12-60mm+15mm/1.7), you end up around 800g, while the A7C with the Tamron 28-200mm or Sony 24-105mm is around 1.1kg. Is that such a significant saving worth sacrificing the capability of the system severely? Only if you don't have the budget for FF, I'd say.
And this in not theory, this juggling with lenses is what I did for many years as an M43 user, before switching to FF and cutting down the number of lenses I really need.
Do I say that a smaller and more convenient 24-120mm/3.5-5.6 lens on E-mount would not be nice to have? Not at all, though I would not replace my Tamron for that. The point is that a dim M43 kit lens is not a fair comparison, as it can't competently work on its own and needs at least a prime or two.