Made several comparative shots with the current roster of lenses I use (or intend to use) with Lumix GF3, one of the world's tinyest system cameras that I'm happy to have. Two of them are native micro four thirds, the other two (low-end ones which I bought for fun) are T-mounted and have fixed aperture and manual focus. I also have several filters for the 14mm lens, so there's a couple of extra shots with them.
The images were taken from a bird-watching tower using a flimsy tripod. Common settings: aperture priority (F8), auto white balance, ISO 160 (except for the IR shot). No post-processing.
Lumix G 14/F2.5. Exposure: 1/800 s.
Same lens with CPL. Exposure: 1/250 s. Slightly more bluish sky and darker water.
Same lens with IR filter. Sensitivity: 400 ISO; exposure: 6 s.
Holga 25/F8. Exposure: 1/400 s. Noticeable vignetting, retro quality.
Lumix G Vario 45-200/F4-5.6. Focal: 45 mm; exposure 1/640 s. Getting close.
Same lens. Focal: 200 mm; exposure 1/500 s. Even closer.
Same lens and settings. 'Extended tele conversion' (lower resolution, more magnification).
Samyang 500/F8. Exposure: 1/640 s. Lacks sharpness no matter what, provokes old-school feelings.
So what's the time now? Well, with some effort the church-watcher's eye says it's like 4:25 pm. But seriously, the whole things has turned out to be not only about focal lengths and how far they can shoot. While the native lenses are my proven reliable performers, I'm still giving more chances to the manual ones, since they give me chances back to do artistic photography on the spot like in old good film-camera times.