Difference between 18-55mm and 18-200mm lenses?

[batmura]

Please excuse me if this is a stupid question, but I'm a beginner who's had his first DSLR for only a month (D3100). I have the 18-55mm kit lens and have read quite a few posts both on this forum and places that carrying an 18-200mm lens does not necessarily ensure better picture quality. Since I'd like to carry only one camera and lens at this time, I'd like to know how an 18-200 differs from a kit lens except that it allows you to zoom in more. I know many people still favour the 50mm lenses to shoot even if they have the 200. If I shoot a pic at 55mm on the 200 will the pic be different from the one on the kit? If yes, I'd like to know the reason.

Also what is the reason for owning 55mm prime lenses? I assume those are the ones that do not let you zoom in or out at all except for changing f-numbers. Wouldn't it be better to have a 18-200 and just set to 55 and the desired f number?

Finally, can anyone tell me about the 17-55mm? How is it different from my kit?

Thanks a lot!

 

[Yantropov]

Obviously, the 18-200mm will provide a longer range... The 18-55mm will be at f3.5g at 18mm, f4.8g at 35mm and f5.6g at 55mm. The 18-200mm will be at f3.5g at 18mm, f4.2g at 35 mm and f4.8g at 50mm which means that the 18-200mm will be able to let more light pass through during an exposure than the 18-55mm at equivalent focal lenght.

Image Quality should be the same on a 18-55 and 18-200 (I have not tried any of those). If you like to travel with only "one" lens, the 18-200 would be more appropriate...

The 17-55mm f2.8g will remain at f2.8g (fix aperture) from 17mm to 55mm. This is what they call a "fast" lens.

 

[KmH]

10x+ zoom range, 18-200+ mm zoom lens are known as a super zoom lens.

To achieve a 10x+ zoom range, a lot of lens design compromises have to be made. Consequently, most superzoom lenses have some image quality and other performance issues, particularly when used at or near any of it's limits of focus distance, focal length, or aperture.

Nikon's 18-200 mm zoom has severe and almost uncorrectable barrel distortion at 18 mm. The barrel distortion diminishes as the lens is zoomed to longer focal lengths and changes to pincushion distortion at about 35 mm.
Focus is soft at 18 mm, improves with focal length, and then starts getting soft again as the 200 mm focal length is approached.
If the Nikon 18-200 is zoomed to 200 mm but then used near it's close focus limit, it only provides the magnification normally delivered at about 135 mm.

Many people value the convenience of a superzoom lens, and are willing to accept the image quality issues. Lems makers sell quite a few superzoom lenses.

 

[otto0713]

Most pictures that make magazine pages are shot with a 50 mm lens, that being said, its probably the most common lens out there and because of its fixed mm (millimeter), its considered "prime" and usually has a large aperture of f1.4 or f1.8. The bigger the aperture, the "faster" the lens is. By faster I mean that the shutter speed will not need very much time to lapse for a decent exposure. They tend to allow faster shutter speeds and hence easily captured moving objects or "freeze movement".
The 18-200 mm lens has to deal with huge magnification factors and therefore may "barrel" the image down near the 18 mm range. Think about it like this. A "prime" lens doesn't have to amplify the scene; as it has only one lens-whereas the telephoto may have several "groups" of lenses, each with many smaller specialized optical lens used in its own function used to "amplify" the scenery to capture a portion of your "field of view." Anytime that light is deflected or refracted to any degree, you will have some distortion. The less amount of "glass" that an light beam has to encounter, the better the image. Although most camera shooters know this, they still use their long telephoto lenses to "pull in" their picture, rather than moving closer to the scene or object, usually resulting in a less than ideal capture.
By the way, no question is stupid.