I recently got the 18-105G lens for use on my Sony Nex-6 e-mount camera. I think a lot of people have been waiting for an upgrade to the kit lenses (at least for the APS-C sensor e-mount cameras), and recently Sony gave us two options: the CZ 16-70 and the 18-105. The CZ is fairly expensive, and the 18-105G is still pricey. I think many people will make-do with the kit lenses which work pretty well overall. But if the bug bites you, that feeling that you just want a bit more quality, you can do that… for a price.
I did some basic testing, and results were what I expected. Sony reserves its “G” designation for lenses that are of particularly high-quality. While the lens is clearly high-quality, it has become apparent that Sony designed the lens with software-correction in mind to control the distortion that is present at most focal lengths. They did this with the 16-50PZ, which made sense, being a collapsible zoom and all – one would expect some compromise to maintain the small form-factor – but why the 18-105G? I suspect (as I’m not a lens designer by any means!) that in the past, a particular lens design might need additional elements to attempt to correct the distortion of a more simple design. Adding more optical elements in the path will cause its own problems. So, you can get degredation optically or through software. The difference, which you seldom see mentioned on the internet, is that with software, you can choose to dial back the distortion correction, allowing for more sharpness to come through. You don’t have the option of removing an optical element! (For wider angles, I often prefer less correction as a bit of barrel distortion will make people’s heads look normal, while at the edge of the photo. Perfect geometric distortion correction is good for preserving straight lines for architecture – not so good for group photos.)
I think a lot of people will appreciate the 18-105G for what it is – a high-quality, better-than-the-kit-lens option. Like many e-mount lenses, there are some compromises, which one may have to accept. The alternative is the much more expensive 16-70, or prime lenses. If on a budget and wanting the highest quality, prime lenses are the way to go, but then you lose the convenience. The 18-105G covers a great range for most general use, and at a constant f4, it can be used in many situations.