Windows -- NEX-5N & Vivitar Series-1 28mm f1.9
Last time I wrote about my favourite wide angle primes, I didn't list the Vivitar Series-1 28mm f1.9. See, this is the problem of having too many lenses. In fact, The 28mm f1.9 is one of my favourites. I believe that when this lens was introduced, it was one of the fastest 28mm lenses on the market. Almost everyone else has the 28mm f2 or f2.8. Many consider this lens as one of the Vivitar Cult Classics, for a very good reason.
Fire Hydrant -- NEX-5N & Vivitar Series-1 28mm f1.9
Apart from its very fast maximum aperture of f1.9, its optical quality is also excellent. It's quite sharp in the center at wide open, and it has the strange and unique exploding bokeh, like this, and this. The build quality is also superb. Very heavy for a 28mm lens. A fantastic lens for full frame as a general use fast wide angle lens.
Very enjoyable lens to use, and worthy of a space in your camera bag (or lens shelf).