I am considering buying my first DSLR.
How do I know whether I need a 18-200 lens, 17-85, or 18-55? Or something else?
Lens questions are probably the hardest gear recommendation questions to answer.
It's unclear if you're a seasoned photographer, or just starting out, so my question is geared towards a person new to photography.
Don't think about it. Buy a lens that fits in your budget. Make it easy and get the kit lens (the lens that is packaged with a camera body).
It won't have all the fancy bells and whistles, but it will be general purpose, won't break the bank, and will let you concentrate more on taking pictures and less about gear.
The bad habit I see with so many photographers who have an online presence is that they sweat the minute, technical details. It's fun to do, but it's also orthogonal to the real goal (imo): producing great photographs.
So, keep it simple. Get the kit lens. Learn what goes into make a great photograph (SUPRISE: IT HAS NOTHING TO DO WITH CAMERA GEAR!), and have fun. Then when your kit lens starts holding you back, come back and ask away.
I think it depends largely on whether you know what you want to take photos of or not. I think if you do then this will have an influence over the lens you choose, in terms of reach, maximum aperture and stabilisation.
I'd also consider a fast prime, such as a 50 f/1.8 that can be bought cheaply for most cameras, as a possible first lens. It's certainly the lens that improved my photography the most once I'd worked out what all of the controls did.
That depends entirely on what kind of shots you are most likely to make and how much weight you are willing to carry.
Assuming you are going for only one lens, the above mentioned lens would be better for:
Other than that, you may want to check the maximum aperture of the lens. The smaller the number (say 2.0, 1.8 or even 1.4) the better the lens for low light situations and portrait shots.
As already said here, the lens choice depends on your needs but I would suggest two alternatives, either:
If you intend on shooting people and portraits - especially in situations with limited natural light available - I suggest you go for the 50mm/1.8 (or a similar lens). It can still produce great photos in situations where your 'kit zoom lens' requires really long exposures and thus produces blurry, out-of-focus photos. Furthermore, the shallow depth-of-field makes portraits look much better.
I'd stay away from the 18-200 lenses. In general, that kind of do-it-all lenses tend to be compromises. If you're going to join the Nikon side, the Nikkor 18-200mm is said to be a good lens but then again its no bargain either. I think there isn't a decent 18-200mm lens for Canon.
my 2 cents,
I don't know if this factors into your decision at all, but one of the things I've been pretty surprised about is how well used equipment (especially lenses) tends to hold its value. It's very possible that you could get into a lens today and decide you want to change to something else in a year and sell the lens without taking a big bath.
You might find that the most effective way you can answer this question is to get any lens at all (of halfway-decent quality), and then shoot with it until you know why you've absolutely got to have something else!
Andre's answer is good. My experience is:
I started with a 18-70 one (3.5-5.6) and later when I learned what I liked to shoot I bought additional lenses.18-200 is usually very expensive to buy for a first lens when you are not sure what kind of a photographer you are.
After playing around with some friend's cameras, I chose the 18-200 in the exact same situation. It is a bit pricey, but I love the flexibility of the lens. I have since picked up a couple more lenses, including a big heavy 70-200 f/2.8, and still like the 18-200 for a lot of situations. Especially when I was just getting started with the DSLR world, I didn't want to have to mess around with changing lenses and miss the shot.
The lens also seems to hold its value pretty well, I picked up mine for $600 and I see other folks selling them on Craigslist for $550, so if you end up deciding to go another way you won't have lost all that much money.
I think a lot of the folks here like primes, but I wouldn't recommend them to someone just getting started. They are great once you understand the basics, and they are cheap enough to get into later (some of them at least!)
It depends on what you want to take pictures of:
If you want to shoot small bugs and other macro stuff, obviously you need a macro lens.
If you want to shoot architecture or landscape, you'll probably want the widest lens possible.
If you want to shoot wildlife, you'll want a long lens (200+).
Probably, as a starter, you don't even know what you will take pictures of. In that case you might buy anything and start with that until you learn what you need.
As a starter I loved long lenses. 200mm and more. For me (and a lot of other fotogs I know) this wears off after a while.
Nowadays I take nearly all my pictures with a fixed 50mm lens. I do own 24-85, 18-200 and a few other zooms, but I just love working with the fixed lens more.
If I'd need to choose just one lens for the rest of my life, it would be a fixed 50mm.
The 18-200mm lens is a great walk around lens. It allows you to have a pretty wide working area for a fairly low price. I shoot on Nikons and just love my Nikon 18-200mm VR. The 18-55/17-85 are good ranges too but they just don't have the same reach. It really comes down to your budget and needs. As a side note before I bought the 18-200mm I had an 18-55mm kit lens and a 55-200mm lens. Getting the 18-200 meant I could take more photos faster with less change of dust and sand getting into my camera body... and that's a really good thing :o)
You may want to think to put more money into your lens collection because new bodies will come out every few years. And as long as you take care of them your lenses should have no problem out living your bodies. Assuming the manufacture doesn't change the mount on you. (The Nikon F-Mount hasn’t changed much since it came out in 1959.)