See my Sigma mirrorless wish list.
I take a look at the Sigma sd Quattro H from ISO 100 to ISO 1600.
Image at sizes up to full 25.5 megapixel resolution, with RawDigger histogram and Sigma Photo Pro settings.
I have to wonder why such a specialty camera just does not stay on-mission and offer a base ISO of 50 or 64 and at most one higher ISO, like ISO 100. Or even just one base ISO.
The idea that ISO 1600 is useful is certainly true—to someone somewhere—which is what wrecks the best designs. I don’t use a screwdriver to pound nails, or eat soup off a plate. Let the tool be true to its potential, which means eliminating all the stuff that clutters it.