Vivitar Series 1 90 f/2.5 macro. is it any good ?

That particular Vivitar has a very good reputation. I believe that all 90/2.5 macro lenses were of the first generation of Vivitar Series I optics, which were as good as were available.

Now, that particular lens may have been dropped or something and not be up to par, but I think you can reasonably expect it to be very good.

I've owned one of these lenses since 1978 or thereabouts. I don't own a Nikon D-SLR (yet) so my comments only apply to film work. The lens is well-built and yields sharp, flat-field images. My only complaint is that there's a lot of glass, especially with the 3-element macro corrector/extender, so you have to be careful about internal reflections; use a lens hood when possible. With the D70's lens magnification factor your effective focal length may seem long for macro work?

I use to own one and it's very sharp. Unfortunately it also suffers from excessive flare and ghosting in adverse lighting. Under good lighting conditions though, it's great.

At the time it came out; it was the sharpest lens the photo mags had ever tested. It tested at 109 line pairs/mm at F11 and F16; on axis; AND the corners; at a 1:9.7 Mag. This lens was designed by an USA design optical design team in the North east I think. The one I have is a nice lens; with a quick focus. Many of these lenses were sold; they are way more common than the 105mm F2.5 VIVITAR Series lens.

There is also a VIVITAR 90/2.5 macro of the same era; that is NOT a series 1 lens; that is decent; but has somewhat more corner darkness wide open. These lenses where made at the same time; and may not have been made by the same maker.

I had this lens for two decades and it was a wonderful performer on a series of Nikon cameras. Most often I kept a 2X (Nikon) TC with it and the resolution still held up. After more than 20 years of hard use, the lens barrel started to get a little wobbly and the diaphragm blades began to get a little out of alignment, so I'd check those items on your potential purchase. But it's a great lens.

I borrowed it briefly, and though I finally went for the 105/2.5 because it goes to 1:1 by itself, I can vouch that both these lenses look blisteringly sharp to my eyes.

-A

I had one years ago. Very Sharp. I have a 16X24 hand held enlargement made on K64 that really is good. Mine finally wouldn't stop down past F:16. I finally sold it when most of my copy work was handled better by a 60mm Nikkor (flat objects). I never used the 1:1 converter so I can't comment on that. The lens is heavy to carry, but as I said, super sharp.

I agree with the veteran users of this lens who have posted above.

This lens made me retire most of my micronikkors.

It is an optical gem without any parallels.