Well, I've just spent a boring hour shooting a brick wall with the NEX on a tripod with various lenses:
Kit Lens at equivalent focal lengths (i.e. 18,24,28,35,55)
Leica 28mm f2 summicron ASPH
Leica 35mm f1.4 summicron ASPH (new version)
Leica 35mm f2.5 summarit ASPH
Leica 50mm f1.4 summilux ASPH
each tested at:
1.4, 2, 2.8, 4, 5.6, 8 (or starting at widest aperture)
Whilst I was about it I stuck the X1 and the M9 (with the 35 'lux and 50 'lux) on the tripod and banged away a few more shots.
I've been peering at the results, and I've come to the following conclusions:
1. all those Leica lenses are fine on the NEX - right to the corners - at all apertures. They do lose a little wide open, but neither vignetting or smearing seem to be a real issue.
2. the 35 'lux is better than the 35 summarit towards the edges and corners at all apertures (more so wide open)
3. the kit lens really does quite well comparison (distortion and CA is an issue of course). If you don't want the speed of the leica lenses, then with this test the Kit lens is really almost as good at the centre as equivalent apertures as the leica lenses costing 10 times as much. Corners are less good, but still mostly acceptable
4. the 24mm lens on the X1 is marginally better than the 28 'cron on the NEX at equivalent apertures. (unfortunately I didn't have a 24 leica lens to
5. If you're wondering how the NEX compares with the M9 with equivalent lenses, then you can stop wondering - It's like a different world!
brick wall tests tell you little about the drawing of the lens or how things look in real shots, added to which, in lots of situations some softness in the corners doesn't much matter anyway.
I was doing these for my own enlightenment, and I have come to some conclusions . . . .
1. I'm only going to use Leica lenses on the NEX in low light situations where using the LCD is more discreet than the M9 (i.e. when having a camera at one's eye is more obvious than the clatter of the NEX shutter).
(worth noting that I shot 100 snaps last night with the 35 'lux at f1.4 and the NEX at a party - it worked really well, good focus hit rate, good colour and low noise at ISO 1600)
2. If I want a little package with a fixed lens then I'll probably use the X1 rather than the NEX and the Leica summarit.
3. I'll use the NEX kit lens with even more confidence.
4. I'll use the M9 if I'm really keen on detail and definition (or the A900 of course)
But, basically, all of these combinations produce decent results - no great surprises for me I think.
For What It's Worth.