Like many old lenses, flare is a real problem, and this one is no exception. Stray lights entering from the front of the lens causes the picture to have a hazy effect. I am sure a proper lens hood will help immensely, but the thread seems like an oddball size of around 40/41mm, and I don't have the original. So, flare resistance is next to nil. You should avoid flare situations unless it's the effects you are looking for.
The lens has no vignetting on the NEX, but edge is still pretty bad, as it was designed for 16mm movie film. For those of us who like old cine lenses, edge to edge sharpness is not one of the criteria we are looking for. Bokeh, image rendering characteristics, and the fact that you can use a decades old lens that was not even designed for this purpose, on a digital body and make images with it, is kind of exciting to look forward to. Let's face it, modern lenses are so common. Anyone can go to a shop and buy one. Image characteristics from the modern lenses is the same as your next neighbor's lenses. What we are looking for is something different. We are not talking about image content, of course, just how the images are rendered.
Most cine lenses are very sharp in the center, and this 50mm f1.4 is no exception. I like how the images are rendered. Very smooth transitions for highlights without abrupt clipping. I have always been very partial to Kern-Paillard lenses for the bokeh. The Switar 25mm f1.4 was one of my favourite lenses and the bokeh on that lens is sweet and arresting, and I am VERY sorry I sold it and this is the reason I don't like selling my lenses.
I am hoping I can find an adapter that can make this lens focus to infinity, in order to use the full capability of the lens.
Switar 50mm f1.4 on the right, Pizar 26mm f1.9 on the left. Click to see larger.
Bokeh -- NEX-5 with Kern-Paillard Switar 50mm f1.4. Click to enlarge.
Ryan -- NEX-5 with Switar 50mm f1.4. Click to see larger.