Regarding Viv S-1 glass. There are numerous (8) Series 1, 70-210 lenses. However, for the sake of discussion, we will deal with the first five. The 4th & 5th editions are nothing to seriously consider, so we will concentrate on the first three editions, which are the good one's. The 4th & 5th editions are also 2.8-4 variable aperture model's, but lacking in construction quality (Cosina built). Due to the fact that the third one is a variable aperture lens, (2.8-4) it will be somewhat sharper than a fixed aperture lenses. It is much easier to design and build a quality variable aperture lens.
The first edition was designed by Vivitar (Ellis Betensky of NASA Optics fame,had a hand in it) and built by Kiron. (67mm filter-macro engagement collar) It is a professional caliber lens, with a 1:2 macro feature built into it. It was the first zoom, designed with the aid of computers, that truly rivaled the OEM lenses of the time. That was in "76." It is a very high quality zoom, that will deliver professional quality results.

The second edition (my personal favorite) was built by Tokina, per, Vivitars specs. It too, is a fixed 3.5 aperture, but smaller, lighter and sharper. (62mm filter size). I really like it because of the fixed 3.5 aperture which is nice for focusing in dim light and long range flash work. However, not a true macro, 1:4 life size. However, it deliver's extremely good results!

The third edition was made by Komine, and like the first two, is very well built. It is a 2.8-4 variable aperture lens, and the sharpest of the bunch. It has 1:2.5 life size macro from 100-210mm's, with a working distance of about two feet. Which can be quite useful,too prevent your own shadow from falling onto the subject, or when shooting fractious crittures. (Rattlesnakes) Been there, done that. Can you see a discernible difference in slides taken with either one of them? Probably not! Don't get caught up in bench tests. Any of the first three editions will give you professional-publishable images. I really like this lens, and in time, may become my favorite.

Personally, I recommend the second or third edition of the line. I have and use all three of the first editions, and can highly recommend any one of them. Superb optics and construction.

Also, the Kiron 70-210 f/4, is an excellent performer that deliver's professional caliber results. The Kiron 70-210 f/4, also has a great zoom-lock feature, that locks the zooming collar in place, so that there is no zoom creep or slippage.

If you have anymore questions about the Vivitar or Kiron lenses, or want more detailed information on a particular lens, please don't hesitate to ask. I also have the the production code for the Vivitar lens line, which enables me to identify the manufacturer, and date of manufacture, for any of the Vivitar lenses. Are you aware of the Viv S-1 28-90 the Kiron 28-85 or the Kiron 28-105? As for Kiron glass, well that's another discussion.....

Kiron Kid