As this 100% crop shows, images shot at the baseline ISO 200 are sharp and noise free.
At ISO 400 images are still sharp and noise free.
BY ISO 800 shadow area detail has begun to break down although images at this sensitivity still remain perfectly usable.
By ISO 1600 detail has begun to soften in the midtone areas as the E-PL3's noise reduction algorithms kick in.
At ISO 3200 noise has become fairly widespread, resulting in a softening of detail throughout the image.
By ISO 6400 colour has begun to degenerate as well as detail.
The top setting of ISO 12,800 is really for emergencies only.