Extra Grain with Leica Lenses on an Olympus E-P2

I’m using my Leica M lenses on my new Olympus E-P2, and I’ve discovered they are generating a lot more “grain” than the m-Zukio 17mm lens that came with the camera. I’ve seen it in all conditions, with different lenses (Leica and Hexanon).

While the image is nice and sharp, with some good detail, you can see “grain” in the sky and flat areas.

Now, look at an image show with the same camera but using the m-Zukio 17mm lens that came with the camera.

This is the center of an image shot with the m-Zukio lens.

Notice the sky, in particular. It’s quite smooth, especially in comparison to the Leica lens image.

Now, I have also shot side-by-side comparisons, and I can tell you the same effect is happening there, so this isn’t about differing conditions. Also, I only shoot RAW files, so this isn’t a post-processing issue. It could be related to something the camera is doing when it creates the RAW file — I think the E-P2 compensates for lens distortions — but my real suspicion is that the light is hitting the sensor at steeper angles in the Leica lenses. Really, that’s all I can think of.

Ideas, anyone?