While many people get excited about what new features are on the latest dSLR, any film photographer will tell you that the lens choice is more important than the camera choice. So let’s talk about how you would go about choosing the best lens (and that’s a subjective term).
First off, you want something light. No matter how sharp or fast, if the lens is too heavy then you won’t take it out of your camera bag all that often. If you’re like me, switching lenses is part of the enjoyment of having a dSLR, but I tend to keep the same lens on most of the time — a small, light and super fast Nikor 50mm f/1.4. When I had a Canon film camera, I carried a Sigma 10 – 20mm super-wide angle along with the Canon 50mm f/2, and that’s all I carried, because both lenses where sharp and had qualities/personalities that were very distinct and I loved the imagery I was getting from those lenses. When I switched to Nikon, I picked up a Nikkor 28-80mm f/3.5 – 5.6 for maybe $175, which I use as a workhorse lens… it’s light (made of plastic), reasonably sharp . I keep wanting to replace it though with faster lens, because I have a penchant for low-light and/or high contrast subjects and I need a faster lens.
Part of what you need to do to select the lenses that are right for you is rent several zooms over 5 or 6 weeks (or weekends), and see which lens you use to get the majority of your pictures. You’ll find that a certain zoom provides you with the majority of images that you want to show off (maybe it’s that 10 – 20mm or maybe its a 80 – 200mm or maybe a 18 – 55mm).
Lens sharpness needs to be a critical and deciding factor when you’re selecting what lenses to use. So is speed, unless you’re a pro photographer, you can get away with not having a zoom with a continuous f/2.8 through-out the range of focal length (as opposed to one that goes from f/3.5 – 5.6 as you zoom. You’ll save at least $800, and still get the shots that you want.
You also need to know where you work best (or at least find yourself predominantly taking photos) in terms of focal length. If you’ve rented a lens for a week, and taken a lot of photos and notice where you work at the longer end of the range (over 100mm), then it makes sense to carry a telephoto zoom. Sigma makes a 70-300mm f/4 – 5.6 that many claim is the best bargain out there for an inexpensive telephoto zoom, you should rent it and find out for yourself. I work by the mantra laid out by Robert Capa, if your photo isn’t compelling enough then you’re not close enough, so I’m not afraid to get close (too close some subjects would say) to what I want to photograph, but I do so with a normal or wide-angle lens; that’s my aesthetic. Once you know what your aesthetic is, it becomes easier to choose what lens you want to have.
Unless you’re a pro, you’re only carrying two or three lens for 95% of the shooting that you’ll do. At the end of the day, there are three lenses that you’ll probably own — a wide-angle zoom, a 50mm prime and telephoto zoom.