I love it when people ask me questions - saves me having to rack my brain about what to write about! :) B asked a question on yesterday's post about lenses for travel photography. She mentioned the fact that lenses are expensive so she wanted to buy the right one.
The lens is, without a doubt, the most important bit of equipment you will own. Now I know that's a pretty bold statement but the camera really is just a box with buttons. Yes some have more megapickles and some have better noise and faster shutter speeds and blah, blah, blah. But at the end of the day that all means zip if your images aren't sharp, punchy and full of life. And a good lens will do that for you (everything else being equal).
The first thing you need to do is think about focal length. If you pop on over to the little Search box on the right hand side there and type in something like telephoto vs wide-angle you'll find a heap of posts I've written on these types of lenses and their different use.
You need to know what kind of things you like to shoot and make your lens choice from there. No point buying an expensive macro lens if you really don't feel like photographing little things.
It might seem a good option to go for a lens that does everything. A super zoom that covers from like 18mm all the way through to 200mm. These are nice, light lenses perfectly suited for travel photography but there is a trade-off in quality. I'm sure you all knew it but no one-fit all is going to do everything for you if your aim is to get the best you can.
In terms of having a sharper image you would be better going for two or three lenses to cover the same range. Bulkier? Sure is. More expensive? Most likely? Better quality? Without a doubt. And with the resolution of digital cameras going up and up these days you're not making full use of your sensor if you're not using really good optics.
Once you've worked out the focal length you want there are a few other things to consider. Do I want a zoom or fixed focal lenth? For most travel photography you would probably be better off with a zoom (a personal opinion anyway) just because it gives you the ability to frame pictures really quickly in situations where you can't move for whatever reason.
If you decide on a zoom you need to decide if you're going to shoot it in low-light, or whether you like the really shallow depth-of-field look. If you do then be prepared to hit the wallet because fast f2.8 zoom lenses are expensive, bulky and heavy. But the images are beautiful. An alternative might be to choose a slightly slower aperture - say f4. Any slower will mean that in low light you will have to bump up your ISO to get fast enough shutter speeds to handhold the lens. Of course vibration reduction (image stabilisation or whatever the manufacturer calls it) can help a lot but you'll still have slow shutter speeds which doesn't help with moving subjects.
Another alternative is fast fixed focal length lenses. The old standard 50mm is a favourite - especially when you put it on a crop-DSLR to make it an 80mm or so.
So in short my answer to B would be to figure out exactly what you want to shoot. That should tell you the focal length you're going to need. Once you know the focal length then my advice would be to buy the fastest (largest aperture f2.8, f4) lens your budget will allow. Don't restrict yourself to only your camera manufacturer's brand because independent lens companies make excellent lenses.
When you've settled on to a lens you're interested in head on over to a site like DPReview or Photo Net and see what the forums have to say.
For the record I use four lenses - all Canon. A 10-22mm f3.5 - f4.5 wide-angle, a 28-70mm f2.8, a 70-200mm f2.8 and a 400mm f5.6. I don't always carry all of them with me because when I do I need to go to the gym for a few days beforehand to work up to it! But I do use all of them regularly. Hope this helps B and if anybody else has a question about anything please feel free to post them in the comments.