Choosing a lens for taking pictures

Often we are faced with a bit of confusion when will buy a used lens for photographing. Before buying you should know will be used to capture whether the lens which we will buy it. To be able to produce good image is the lens selection also gives the role his own.
There are several ways in selecting a lens:
1. Make sure the warranty is from a distributor lens brand.
2. When you buy a second lens make sure it is done first test
3. Check the market price and its new price of a distinguished website accurate,
if possible buy who is still under warranty.

And a little extra in choosing a lens for taking pictures:
1. Photographing Landscape use wide lenses (eg 10-22mm)
2. Photographing Human Interest use zoom lenses (eg 18-135mm)
3. Photographing models use a prime lens (eg 85mm)
4. Photographing the macro using a macro lens.

Furthermore, the core of the story this time in choosing a lens:
Things to consider in selecting a camera lens for underwater photography is FOCAL LENGTH. Clearly, focal length is the distance focus point of the camera sensor that determines the magnification factor of a lens. The human eye has a magnification factor equal to the 50mm lens, so the 50mm lens is also called Normal. If we use a 50mm lens, the enlargement does not occur at all against what was seen using a camera and viewed directly by eye. Smaller than the 50mm lens would give a negative magnification factor or in other words reduced accordingly under the 50mm lens is often called a wide-angle lens / wide angle. Similarly, a lens with a focal length above 50mm lens also called Tele for long distances because of the enlargement.
Nikon 50mm f/1.8D AF Nikkor Lens for Nikon Digital SLR CamerasCanon EF 75-300mm f/4-5.6 III Telephoto Zoom Lens for Canon SLR Cameras