TANSTAAFL

Putting larger sensors in smaller mirrorless bodies isn't necessarily a cure-all answer that creates the magically portable camera that still has awesome image quality. Whether it's in a giant Nikon pro body or a comparatively svelte mirrorless Sony, a full-frame sensor is still going to need a full-frame lens hung off the front of that camera.

Pictured below are some roughly comparable midrange zoom lenses for three different size sensors:

At left is the Olympus M. Zuiko 14-42mm f/3.5-5.6, which is the basic little kit zoom for Olympus Micro 4/3 cameras. It's collapsible to make it more portable for carrying, but it's shown here in its ready-to-shoot state.

In the center is the Pentax 02 5-15mm f/2.8-4.5, which was the kit zoom for the Pentax Q system. It's a teeny little thing, barely the size of a shot glass.

Lastly, the right-hand lens is a Sony 24-70mm f/4 Vario-Tessar, which is a zoom for a full-frame Sony sensor. Being a constant-aperture f/4 lens makes it a little bigger than a cheaper variable-aperture lens of the same focal length range, but even its 28-70mm f/3.5-5.6 stablemate is still the size of a middlin'-size coffee mug.

Thanks to the magic of equivalence, which has both upsides and downsides, all three of these lenses have pretty much the same field-of-view range.
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