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Optical Zoom...
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One of the most frequently mentioned features on any digital camera is the zoom lens. Get a Sunday newspaper or check out some ads on the internet. What features do you see mentioned over and over again on every ad?
Besides the obvious ones like the manufacturer and the model of the camera, probably the main highlighted feature is the camera's resolution, or "Megapixels." After that, however, you will generally see prominently displayed either
"Digital" and/or "Optical" zoom. Let's examine:
- What is it?
- Why should I care?
What the heck is the difference between
Optical and Digital zoom?
In a word...everything! Optical zoom is the "real deal." The same concept is used with a telescope or binoculars. If you want to see something more clearly that is far away, it has to be magnified.
If you look through a 50mm camera lens, there is no difference in magnification than if you were looking at the subject with your naked eye. However, the greater the lens size (100mm, 200mm, etc), the greater the magnification.
The sailing ship above was taken with a 28mm focal length lens from approximately 400 feet away.
From that distance and focal length, you can see that the bottom of the boat is green, with a black layer above, topped with a white layer having what appears to be black squares in it.
The second photo is the same ship taken from the same distance, using a 200mm focal length lens. We can now make out the detail and thus realize that the black "squares" are actually cannon ports.
Digital zoom is completely different! After you take a photo and want to check it out, you look at the LCD screen on your camera.
Since most LCD screens are not much bigger than 1 square inch, it's somewhat difficult to pick out any meaningful detail.
If however, you want to "move in" on little Jimmy's adorable smile by moving the camera's digital zoom control, the camera's brain analyzes and expands a small part of the picture.
You will notice that the more you digitally move in, the more distorted looking the picture becomes. The distortion is caused by the image becoming "pixilated."
Why should we care?
When going to buy a digital camera, you will probably see something like the following zoom figures:
- Optical = 4X
- Digital = 8X
- Combined = 32X
The only figure to pay any attention at all to is Optical. Ask them what the equivalent factor is in mm of the lens. Remember that 50mm is equivalent to the naked eye, and there are digital cameras on the market with a 10X magnification (approximately 400mm equivalent).
Digital "Z--m" (I'm taking a stand and refuse to even use the word here) means almost nothing. My personal theory behind the creation of "Combined Z--m" is that marketing folks had WAY too much time on their hands. It's worse than meaning nothing; it's MISLEADING.
When you buy a car, does the salesman try to impress you with the car's "dollar pound" calculation? (That's when you multiply the cost of the car by its weight.) Of course they don't... you'd laugh your way right out of the showroom. If a camera salesman tries it with "Combined Z--m," I suggest you do the same.
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