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Old Mar 5, 2003, 12:54 PM   #1
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Default How does optical zoom work?

I was wondering how far optical zoom goes. I see cameras that use 2x, 3x, etc... optical zoom and I don't understand what that means. How far does each optical zoom go to getting closer to the image. I hope my question makes sense because I am a little confused :?


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Old Mar 5, 2003, 1:26 PM   #2
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Think of it this way (this is a way simplified explanation): 3x optical zoom will magnify the object in the viewfinder three times as much as it would at the widest angle the lens can provide. If, at the widest setting of the camera (= no zoom), an object is 10 pixels tall, then at 3x optical zoom, the same object will be 30 pixels tall.

Keep in mind that the act of zooming in will reduce what can be captured on the picture frame. Things will get bigger, but what you can capture will become narrower.

Typically you'll see something like this on a digital camera lens:

Olympus C-4000Z: AF Zoom 6.5-19.5mm

6.5 - 19.5mm is the zoom range of the lens in the C-4000Z camera. 19.5 divided by 6.5 = 3, therefore the C-4000Z has 3x optical lens.

The 2x, 3x, 4x designations are almost all used exclusively with consumer digital cameras and camcorders. SLR lenses (digital and film) will state the range of the zoom lens and not the magnification factor. For example, one of my Canon EF lens for a film SLR camera is: 28-105mm f/3.5-4.5. In digital terms, this is a 3.75x optical zoom (105 divided by 28).

Want to get really confused? The 6.5-19.5mm lens on the digital C-4000 can't be compared directly to the 28-105mm on the Canon EF lens. Because of the different size of the sensors in digital cameras and SLR cameras (and even within SLRs, there's a difference between film and digital), manufacturers and reviewers will throw in "35mm equivalent" values for their digital lenses. In 35mm terms, the 6.5-19.5mm lens on the C-4000 is 32-96mm. Again, 3x optical zoom.

Hope this clarifies a bit!
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Old Mar 5, 2003, 1:35 PM   #3
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Optical zoom is merely the difference between the camera's widest angle and the narrowist telephoto position. Using the 35mm focal length equivalents (so there's a common reference):

Canon Powershot S30 35-105mm=3x zoom
Fuji finepix 4800 36-108mm=3x zoom
Kodak DX4330 38-114mm=3x zoom
Nikon Coolpix 990 38 to 115mm=3x zoom
Olympus C-3030 32 to 96mm=3x zoom

Obviously some rounding going on, but you can't say you got a 2.9832345x zoom!

Someone in another forum with a 10x zoom camera complained that they only had 7.6x zoom because they were only measuring from the standard eye focal length of 50mm; they were only measuring how much zoom in (or telephoto) they had while forgetting about how much zoom out (or wide angle) they had...so in fact they did have a 10x optical zoom.

You have to really compare the 35mm focal length equivalents of the cameras you're looking at, the zoom factor doesn't say it all. For instance in the list I posted (if I was shopping around) I may want the Olympus because it has the widest wide angle of the bunch...I'd put up with the lower telephoto since I can crop and do some digital zooming on the computer.

My own camera is an Olympus C-700 which I mention because it is a 10x zoom and it has a range of 38-380mm (with digital it can go up to 1000mm, but it's best to do that on the computer later when you can control things more).

Did that get your question answered?
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Old Mar 5, 2003, 2:15 PM   #4
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Thanks guys,

I think that answered my question


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