Opticallimits tested the Panasonic-Leica 50-200mm MFT lens:
The Leica DG Vario-Elmarit 50-200mm f/2.8-4 ASPH Power OIS is an outstanding lens … with one exception. It excels in most of the formal parameters. In terms of resolution, it is extremely sharp across the zoom range. Image distortions are absent in conventionally processed images with just a little distortion present in RAW images. Lateral CAs are negligible. Vignetting is usually auto-corrected so no worries here normally. If you chose to deactivate auto-correction, you may notice an elevated light falloff at maximum aperture though. The biggest weakness is in an informal parameter – the bokeh. Out-of-focus highlights have an odd inner structure and the general rendition of background blur is also harsher than desirable in certain scenes at least.
The build quality is excellent and if you handle it, you can immediately feel the difference compared to conventional Panasonic lenses. The subjective quality perception is even superior to Olympus PRO lenses in our book. It’s still not perfect though. Zoom creeping can be a bit of annoying and some may miss a dedicated tripod mount (especially when using teleconverters). The AF is extremely quick and noiseless. The performance of the optical image stabilizer system is also impressive – and also needed at such long focal lengths. While the lens-based IS is pretty good already, it is a bit unfortunate that Olympus users can’t take advantage of Dual-IS (=combining the optical IS with the in-camera IS system). So if you intend to have this as your primary lens, you may be better off with a Panasonic camera.
If you want a darn-sharp zoom lens, the Leica DG Vario-Elmarit 50-200mm f/2.8-4 ASPH Power OIS is an obvious choice albeit an overly expensive one. For portraits and other “bokeh-centric” applications, you may prefer to look elsewhere though (the Olympus 45mm f/1.2 PRO is superb).