My new E-M5 has nasty high ISO noise bands with 12-50 :-(

(snip)

Thank you very much, you have told me pretty much what I needed to know. Your shots, especially the -3ev, have that curved kind of banding I'm talking about, and the one that has me worried. I'll set up some similar shots tonight in program mode at 0, -1, -2 and -3EV and see if my results are close to yours. If they are, then I'll consider it normal for the camera. If they are worse, then I'll probably go back to the store and see if the display model is more like my results or more like yours.

Thanks again, I very much appreciate it that you took the time to do this.
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Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life.