I'm something of a believer in half-baked photo tests. If test results aren't obvious except in highly-exacting circumstances, for equipment that's unlikely to be used in exacting circumstances, then: who needs them?
If results can be shown in ad hoc, half-baked test situations, then they're more worth examining. So here's a quick little comparison. I'm not looking at bokeh, or chromatic aberrations, or anything else. Just focus near the center.
I was concerned about some wobble in the focusing elements of my Canon 50mm ƒ/1.4 lens. I figured I should compare it to my corresponding rock-solid Contax-Zeiss 50, that I can mount to the 5D via a "Cantax" adapter. And since I was shooting at ISO 100 anyway, why not do a quick comparison against my compact LX1?
What you see above are pixel-to-pixel crops from the centers of three photos. The white-balance was set to "auto" for all, so the color shifts are not significant.
The results surprised me a bit. These shots are all made around ƒ/4, 1/250th of a second handheld but leaning against a wall. I made several exposures & these are 'representative.'
The first surprise, to me, was how poorly the Zeiss lens did compared to the Canon. I had expected the opposite. While it's possible that my manual-focus skills aren't up to snuff when compared to the Canon AF (even with the special Canon 'S' manual-focus screen), I did check the entire frame, and found that there were indeed areas where the Zeiss focus was a bit better than here in the center, specifically in the corners. So either way, the Zeiss had less flatness, or maybe it was just less sharp at the center.
Or I can't focus. Either way, since in this case I only care about photographs that I myself will make, the net effect is the same: I get a sharper result with the Canon, at least for the 50mm. And that was a surprise (I'll have to test the 28mm lenses after the holiday).
I also found that the wobble seemed to have no effect on the effectiveness of the Canon lens (still disconcerting, and I may have to send it in. If I tilt the lens forward or back after locking focus, the elements move and then I do shift focus. I can also feel a distinct "thunk" when the elements slide).
The third surprise was just how well the little compact PanaLeica held up. At ISO's above 100, or in terms of instant-on accessability, the big Canon dominates but for good light, the LX1 (or LX2, which has the same Leica zoom lens) puts up a real competetive fight! Especially for a pocketable camera that costs one-fifth the Canon price (or even less: since the LX2 came out, I've seen real LX1 deals. I ran into one at Fry's last week, brand new for less than $300).