Z is for Zoom
A zoom lens is a camera lens that has the ability to change the focal length of the lens. It allows photographers to take pictures from great distances or get close up shots with just one lens. Zooms are popularly used in photography because they offer versatility and flexibility, but they can be more expensive than basic lenses which only focus at one focal length.
What is a zoom lens?
"Zoom" in photography is a term applied to lenses. We’re familiar with the effect of zoom lenses because we use the phrase “zoom in” in regular daily banter. "Zoom in" means get closer, but how does that work?
Lenses with longer focal lengths (telephoto lenses) are able to make the image viewed through the lens larger, which creates the effect of getting closer. In contrast, lenses with shorter focal lengths (wide angle lenses) make objects seem more distant.
What a zoom lens does is allow the focal length of a single lens to be changed allowing the photographer to choose how large the subject of the photo will be in the frame. This in turn allows the photographer a great deal of control on the composition of their final photograph.
Nikkor 28–200 mm zoom lens, extended to 200 mm at left and collapsed to 28 mm focal length at right. Credit: Marc Lacoste CC By-SA 2.5
How do zoom lenses work?
This is accomplished by having multiple elements within the lens that are moved to change its focal length. This is also why zoom lenses are so much more expensive than single focal length lenses.
The best zoom lenses have to be able to do the following:
- Allow zooming in and out without distortion or vignetting (darkening) of any area
- Have an excellent image quality throughout its entire zoom range, regardless of whether it's at the maximum or minimum focal length
What is the difference between optical zoom and digital zoom?
Multiple element lenses of variable focal length were the original zoom lenses. They require the physical movement of the various lens elements to alter the focal length. It's physics. It's optics. And it works in the absence of electricity and computers.
Digital zoom is a result of a application that enlarges the pixels in an image taken by a digital camera. The image quality is not as good as optical zoom but is included with digital cameras for convenience.
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