Sony showed off their VCL-DH1757 Telephoto Lens for the DSC-HX1 at the Photo Imaging Expo in Japan recently, and it looks pretty slick. Made specifically for a Cyber-shot DSC-HX1 digital camera, this durable lens features a classic black housing and delivers crisp detail even at the edge of the image. The VCL-DH1757 high-grade 1.7x tele-angle conversion lens for DSC-HX1 Cyber-shot camera will be available in early May for $230USD.
Telephoto and other long-focal-length lenses are best known for making distant objects appear magnified. This effect is similar to moving closer to the object, but is not the same, since perspective is a function solely of viewing location. Two images taken from the same location, one with a wide angle lens and the other with a telephoto lens, will show identical perspective, in that near and far objects appear the same relative size to each other. Comparing magnification by using a long lens to magnification by moving closer, however, the telephoto shot appears to compress the distance between objects due to the perspective from the more distant location. Long lenses thus give a photographer an alternative to the type of perspective distortion exhibited by shorter focal length lenses where (when the photographer stands closer to the given subject) different portions of a subject in a photograph can appear out of proportion to each other.
Long lenses also make it easier to blur the background more, even when the depth of field is the same; photographers will sometimes use this effect to defocus the background in an image to “separate” it from the subject.