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Photography Question 
algan nustekin

member since: 7/1/2002
 

What Is"x" Zoom


Hi there,
Could any one tell me what does it mean 3x optical zoom 20x optical zoom, 5x digital zoom etc...

Ok, if I am not wrong optical zoom is set by changing the distances of the lenses in any objectives. But what is the digital 3x or 5x zoom what does it measure? For example, I have 28-80mm objective of my Nikon f55, so now 80 minus 28 is 52, so does it mean that it is 52x or what? What does the term "x" define?

7/1/2003 3:22:34 AM

 
Jon Close
BetterPhoto Member

member since: 5/18/2000
  "x" refers to the ratio or multiple of the zoom range. A 70-210 zoom is a 3x zoom (210/70 = 3). A 28-80 zoom is also approximately 3x (80/28 = 2.86). This ratio of focal lengths is also called the "optical zoom" because it is acheived directly with the lenses. It is also roughly equal to a magnification factor as objects view through 210mm lens appear about 3x larger than with 70mm lens.

A digital zoom achieves the additional magnification electronically by enlarging just the central portion of the image sensor. A 10x digital zoom simply enlarges the central 10% of the image sensor. There is some loss of resolution since the "zoomed" image has only 10% as much information as the full sensor image.

7/1/2003 9:12:24 AM

 

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