This is a tiny and light pancake lens (even smaller than the 16-50mm kit lens!). Performance on the a5100 (you may need to use aperture priority mode to take advantage of this lens). I also have a Sigma 19mm 2.8 lens and have a feeling I'll be using this lens more often as part of a very compact and lightweight kit. although this lens is quite small (a5100 + Meike MK-35mm f/1.4 APS-C lens or Samyang 35mm f2.8 FE lens). I only wish this lens was cheaper!
Nikon 35mm f/1.8G Auto Focus Lens for Nikon DSLR Cameras - Black (Model 2183)
125 Review
Black Canon EF 24-105mm f/4L IS II USM Lens - Model 1380C002
78 Review
Canon EF 40mm f/2.8 STM Lens - Fixed Black (6310B002) for US Cameras
76 Review
Canon EOS SLR Camera Lens EF 24-105mm f/4 L IS USM
124 Review