I was looking for a small, relatively cheap lens to use on my a7rii. I tried a few manual focus options like the Voigtlander Nokton Classic 40mm with a Leica adapter (I have the excellent Yeenon adapter), but that was not exactly cheap, and honestly, the manual focus is nice for artsy shots, but just not quick enough.
So... given that the a7rii has this massive 42 Megapixel sensor (which produces a whopping 80MB raw image!) I thought I would try a cropped Sony E-mount lens (APS-C format) which would still give me an 18 Megapixel (5168x3448) cropped image. So... my hunt got me to this lens...Sigma 30mm f/2.8 DN Lens for Sony E-mount Cameras
At $169, it is a bargain. And even though f2.8 is not very fast, it would work for everyday use, and is the reason why this lens is so small. If you use this on a cropped sensor, it is equivalent to a 45mm lens. I followed a trick I saw on youtube and removed the baffle, which then gives you close to a 35mm usable coverage on the sensor. Have a look at these three shots... the first is a full frame shot with the baffle on, the second is what it looks like when you shoot cropped to APS-C, and the third is what it looks like at full frame, but with the baffle removed.
There is some pretty bad distortion at the edges when you use it on the full frame sensor, so I may end up using it in cropped mode mostly, and just revert to full frame when I need to go a bit wider. Also have a look at this thread for some good examples of this lens on the a7.
Here is what it looks like on my camera compared to my 55mm 1.8 lens.
Here are some other nice shots I took at dinner and at the market. I think the lens did pretty well!