- 35mm film - consumer grade autofocus zooms from system and third-party (cheap construction, small minimum aperture, mediocre image quality).
- 35mm - some fixed-focal length ('prime') autofocus lenses from system and third-party (better construction, better image quality, slightly bigger minimum apertures).
- Medium and large format, 1 or 2 manual focus prime lenses from the system manufacturer (excellent quality, heavy, bigger minimum apertures).
- Digital - pro-grade autofocus zooms (fast, excellent quality but big and heavy, not very discrete).
- Today - a mixture of ~30-year old prime manual focus lenses at the shorter end (fast, excellent quality, compact, light, great value secondhand, superb tactile-feel), Nikon's superb tilt-shift PC-E lenses, with a pro grade autofocus zoom and super telephoto at the longer end (see comment to 4. above).
That zoom mentioned in 5., the Nikon 70-200mm f/2.8 VR was the only zoom I owned. However, the D7000 now forces me to re-evaluate things at the wide end. Whilst my 270g 20mm f/2.8 AiS does just fine for me on a D3, the equivalent 30mm on the D7000 is just not wide enough.
Trouble is, anything ultra-wide tends to be quite heavy (400-500g or more), and/or does not allow the use of filters, (which is essential to me) or gives massive amounts of distortion. The solution? Turns out to be quite simple, and with a little bonus item as well.
Enter the Tokina 11-16mm f/2.8 DX, effectively 16.5-24mm. OK, so it's failed already on my first point, weighing in at 560g - but, hey, you don't get a lens built like this without it packing a few grams! Seriously, this is one well-built lens for the money. It's at least as good, if not better, than any recent Nikon zoom near this price point. The focus ring has a good feel, and the simple clutch to engage/disengage autofocus by moving the focus ring back and forth works better than expected (I'll probably leave it on manual though).
It's a 'G' type lens in Nikon speak, which means there is no aperture ring, the aperture has to be set on the camera. Focus and zoom orientation is the same as Nikon's own lenses. Comes complete with a hood, and the filter thread is 77mm, just like Nikon's own pro-zooms and PC-E lenses. I've tried a Lee wide-angle adapter and 2-slot holder and it doesn't vignette even at 11mm.
How about that weight though? Well it is a bit of a lump, but lighter than a couple of ultra-wide primes and although there are lighter ultra-wide zooms out there from Sigma and Tamron, it's nearest competitor is Nikon's own 10-24mm, which is only slightly more expensive. The Nikon does weigh 100g less, but that's reflected in the build quality.
But what about that bonus item? Well, the Tokina lens also works on full-frame! Obviously this is not what it was designed for, so there is vignetting at the wider end, but at 15 or 16mm it works just fine, if stopped down. You can even go a little wider if you crop to 5:4 (thanks to Ken Rockwell for pointing this out!). This in itself was enough to persuade me to Tokina away from the Nikon 10-24mm, which only manages 18mm on full frame, according to Ken. Obviously if you never intend to shoot full-frame then you may be better served by the Nikon, but it you truly 'never-say-never', then may be the Tokina is a better long-term investment, coming as it does, with a 'free' 15/16mm full frame lens.
Back to my evolutionary journey to photographic nirvana: save yourself some money, ignore the first three in my list above: we're in the age of digital now and none of these cuts it in my opinion any more. Which leaves you with 4 or 5, pro-grade zooms or pro-grade primes, same as it's always been really.
The choice here comes down mainly to what you shoot and where you shoot it. I don't need autofocus for many things, and I don't need to switch from one focal length to another in an instant: but if you're a sports or wedding photographer, these things are probably vital to you. The important point is buy the very best glass you can afford: treat it as an investment that should span the lifetime of many digital bodies!
One more thing, if the budget is tight, then a beaten up old fast prime, as long as the optics are good (and it's so easy to test now with digital), is worth 10 slow plastic 'kit' zoom lenses, any day. Can't get the exact focal length you want or is not having a zoom the end of the world to you? Try using your legs.