Originally posted by: archcommus
Can I ask an honest question? I know nothing about photography but I hear people on here rave about lenses all the time. What's so special/important about the lens? What does a $600 lens do differently than the small one that comes in a standard digital camera?
The photographer makes the image, not the lens or the camera. Better equipment can make a particular job easier, but I heard a story from a guy once about a photo class. The instructor led a field trip for students to take pictures. They all had their SLR's, and the instructor used a disposable kodak or something. Several of his pictures turned out better than anything the students took. He knew his limits, and had to stay within them, which made it harder to take photos because he couldn't take what the camera wasn't able to properly expose, but he made a point that the camera isn't the most critical thing.
Now, the lens that I took this with is a $1700 lens. The reason I needed this lens is because it can shoot in low light. It has a 2.8 aperture through the whole zoom range and Image Stabilizer.
So if I'm shooting a wedding in a darker lit church, I can shoot at ISO 1600, 2.8, and 1/30th of a second, handheld, and still get a good sharp shot because of the IS. It just wouldn't be possible to shoot in that situation otherwise (without flash). That's a case where the lens is needed, and the cost justified.
I've seen some really great photos with the 18-55 Canon kit lens. If you know the limitations of it you can work around them and produce excellent images.
You just have to research and find good quality lenses which are not as expensive. Such as the Tamron 28-75mm Di XR LD - it's about $350ish, but has excellent optics and a 2.8 aperture though the whole range.
So to answer the question, the more expensive lenses usually are "faster" which means they have a lower f/number (aperture - the smaller the number, the larger the opening). They also usually are able to use the same lower aperture through the whole zoom range, while less expensive zooms must use a higher aperture number (smaller opening) at the long end of the zoom. The smaller the opening, the less light you can let into the lens which means you are limiting yourself as far as what conditions you can shoot in. You can still shoot indoors with not a lot of light, but you have to use flash. Sometimes in weddings, flashes are not allowed.
So there are many reasons why the more expensive lenses are needed - depending on what type of work you do. I have to spend the money. I do portraits and weddings and such, and my results need to be good. My 70-200 (the one I shot these with) allows me to shoot in low light without flash, as well as be unobtrusive. I can zoom in and catch details of a wedding without being right in everyone's face.
I also shoot a lot of shots with my 50mm f/1.4 prime. It's about a $300 lens. It doesn't zoom, but offers some of the sharpest results of any of my lenses, and lets me get a tiny, thin DOF @ 1.4 for creative shots. Canon also makes a 50mm f/1.8 prime which is under $100, and can also take amazing shots.
So no you don't need expensive lenses to take good photos. But they can help an already good creative posing and composition/exposure of photos by getting sharper and more properly color saturated results.
Bottom line is just that the photographer has to know the limits of the equipment, and be able to work within those limits. If he/she can do that, then some awesome pictures can be had.