ISO 200 is sharp, detailed and noise-free.
ISO 400 shows very little difference from ISO 200.
At ISO 800 the E-M5 is still producing high quality images, with only the merest hint of noise.
At ISO 1600 noise has begun to creep in with a softening of detail, but it's not a great problem.
ISO 3200 shows a more marked increase in noise, with a more noticeable softening of detail.
ISO 6400 is where image quality begins to break down, especially when viewing images at 100% or more.
At ISO 12,800 and image quality is starting to get a bit ropey.
The top setting of ISO 25,600 might help you out in an emergency but is otherwise best avoided.