It seems like I've been doing a lot of "comparing things" recently. I just posted a long article, as a result of a lengthy (and not always happy) exploration of film scanning, over in hybridphoto.com, with results that surprised me at first and on further thought, educated me about what kind of photographer I am (or at least informed me about the medium I work in.) I suffer from a severe case of G.A.S., and as a result I tend to think of myself as a gearhead. I'm also trained as a scientist, and I think of myself as a technically-oriented photographer. Then Kiron Kid asked me what I thought of a particular lens -- the Vivitar Series 1 28-105 -- and I thought, well, I'll just go out and shoot a bit with it (which I did) and since I had just bought a Nikkor AF35-135 to go with my new (to me) F5, I followed up with a few shots with it as well (both lenses on my D700, so I could see the results quickly and easily.) The results were, well, different. There are things I can say technically about the two lenses -- the Vivitar has enough light falloff that you'd probably call it vignetting, at least at some apertures and focal lengths while the Nikkor has none that I can see. On the other hand, both lenses have distortion at the ends of their focal ranges, barrel at the wide end, pincushion at the long end, at it's actually worse on the Nikkor at both ends. Either that or my brick wall is doing some strange things. The Nikkor's also sharper in the corners wide open (honestly, stopped down, too) and probably a tad sharper overall wide open. It's also more contrasty throughout, but that actually made the one shot I made in macro mode (of a single orange blossom) look better -- less washed out and showing more detail -- with the Vivitar than with the Nikkor. The corner sharpness was irrelevant in this one shot, and the slight vignetting actually worked with this image. It seems to me that I could get a tad closer with the Vivitar, too, but honestly I wasn't making measurements.
But the thing I noticed most was how differently I worked with each of these lenses, which on the surface are very similar. Part of it was that I tended to be more involved with the Vivitar, maybe because it's manual focus I was just more hands-on in general. I'm still learning what the F5 can and cannot do and with the Vivitar (which I had used before on older Minolta gear) I maybe just reverted to my older set of manual everything skills. With the AF Nikkor, I tended to let the camera do what it wanted to. I think in retrospect, I could have gotten better exposures with the Nikkor if I had been more involved, like I did with the Vivitar, and perhaps controlled the contrast better in the macro shot. Or maybe not.
Anyway, even if the Vivitar isn't as "good" a lens as the Nikkor, it's still an interesting and "useful" tool. It'll probably find a home on my FG (or my new Nikomat EL) and get some use. See, I've mentioned 4 cameras in this post, three of them new acquisitions. I really am a gearhead!