I did, however, go out during the week to try out the Vivitar Series-1 35-85mm f2.8 zoom lens. I have had this lens for at least a couple of years but only took a couple of test shots after I bought it. This particular one came in Minolta MD mount, but I also have the M42 version, which is not in as good condition as the one in MD mount. Both behave similarly in optical qualities.
Sick Leaf -- NEX-5N & Vivitar S1 35-85mm f2.8. Click for larger.
The Vivitar Series-1 35-85mm f2.8 is one of the very early constant aperture f2.8 lens. I wonder if it shares any optical design from the Zoomar 36-82mm f2.8 lens. In any case, this is not a parfocal lens, meaning that it does not keep the focus when you change focal length. Instead, it uses a variable focusing, which makes the design simpler, but you have to refocus when you change the zoom position.
Art in the Park -- NEX-5N & Vivitar S1 35-85mm f2.8. click for larger.
We all know the zoom lenses have lots of compromises optically and they are complex to design. Early zooms were never really good, especially the cheap ones. This particular one was the premium zoom lens from the Series-1 line with VMC coating, and was/is considered one of the better lenses from the time this lens was introduced. In fact, this is one of the Vivitar cult classics. It's a pretty impressively made lens, but I don't like the zoom action. It's not very smooth. Optically, it's pretty soft at f2.8, but usable with some post processing if the subject of interest is in the middle of the frame. Stopped down to f8, it's actually quite good, especially for a zoom lens this old. It's just can't compete with today's modern zooms with similar focal lengths, but than again, the biggest selling point for this lens was the larger f2.8 maximum aperture through out the zoom range. This means in low lights, it means getting a picture or not at the safe shutter speed. In terms of the bokeh, it's kind of messy but not ugly.
Would you buy one of these lenses? I guess it all depends on how much you want to spend. I certainly wouldn't spend too much money for it and would consider a auto focus zoom, unless f2.8 is important to you and you can't afford an auto focus version. Others might buy this lens for nostalgia reasons, or for collecting. For practical use, a modern zoom lens is the way to go.
Bokeh -- NEX-5N & Vivitar 35-85mm f2.8 @ f2.8