ISO 3200 on an Olympus camera is noisy. It’s not unusably noisy, but if you pixel-peep, you undeniably see noise.
It’s not really worse than the noise of a high-end Nikon or Sony camera with between 30 or 45 megapixels, it’s just that you have only half of the pixels and are more likely to peep.
The current trend is to keep pixel size constant and to produce sensors with the same density and different sizes. After all, in most cases we talk about variations of the same Sony technology.
In the end we look at our images at the same sizes, regardless of the camera they’ve been made with. At least for screen view, we downsize radically. While downsizing, we also downsize the noise. More pixels means more downsizing of noise and therefore less apparent noise. That’s why the essentially same sensors in “full frame” cameras get better noise ratings than their Micro Four Thirds counterparts.
Of course you can also have big sensors with a small number of pixels. Sony tried that with one variation of their A7 line. Theoretically the noise should be lower, but if you look at DxO test results, the high pixel count sensors still lead. After all, downsizing seems to be the better strategy and it is more versatile in any case.
Speaking of DxO, this image has been converted with DxO Optics Pro. The algorithm is much too slow for in-camera processing. For each pixel it looks at 1000 neighboring pixels. I’s applied math and it works extremely well, even with half the pixel count 🙂