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Old Mar 19, 2006, 11:39 AM   #1
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Sirs, I am not an expert, so please explain to me....

What is the difference between, say, zooming in on a distant subject with a 5MP camera that has a 10X optical zoom, and taking a photo of the same distant subject with a 8MP camera (3x zoom) and then enlarging/cropping it on the computer??

Would the finished products have the same clarity (resolution). I am confused at the relationship between zoom and higher MP.
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Old Mar 19, 2006, 12:29 PM   #2
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Checking on a couple of sample cameras I see that 5Mp is 2592 x 1944 and an 8MP camera is 3264 x 2448 so all things being equal a 2592 x 1944 crop from an 8Mp camaera will have the same detail as a 5Mp camera. That's not giving you anything near a 10x zoom from a 3x zoom camera although x times zooms are fairly meaningless until you know where they start and end. For example a 50 - 500 mm zoom is a 10x zoom so is a 20-200 but they're very different lenses.

Also as I said it depends on all things being equal not all lenses are the same quality so a 5Mp camera may give far better results than an 8Mp camera. The other issue is that when it comes to MP more isn't always better, crowding 8Mp onto the same size sensor as 5Mp sometimes the result is a poorer quality sensor.


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Old Mar 19, 2006, 12:55 PM   #3
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arrowspace90 wrote:
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Sirs, I am not an expert, so please explain to me....

What is the difference between, say, zooming in on a distant subject with a 5MP camera that has a 10X optical zoom, and taking a photo of the same distant subject with a 8MP camera (3x zoom) and then enlarging/cropping it on the computer??

Would the finished products have the same clarity (resolution). I am confused at the relationship between zoom and higher MP.
This is a subject that has come up quite a bit. Consider that to double the size of an image at the same resolution requires 4 times as may pixels. This is because it is an area function, therefore the second power.

To crop an image and enlarge to give equivalent of 10x means using only 1/100th of the image.

8MP *3x zoom/ 100 will in no way give the same image as 5MP * 10x zoom.

Also, the zoom is only a ratio of shortest to longest focal length of the lens. In order to compare, you must know the actual focal lengths.

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Old Mar 20, 2006, 12:10 AM   #4
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Thanks for these very helpful explanations. You guys are digital while the rest of us are analog.
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Old Mar 20, 2006, 10:40 AM   #5
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This is a geocities site, so it's got advertisements and popups. But, you may find the chart (and links to Telephoto Figure of Merit articles) useful:

http://www.geocities.com/digital_ray...oomzoomv7.html

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Old Mar 21, 2006, 12:53 AM   #6
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OK, how about if the lens was able to zoom to the equivalent of a 35mm lens to 350mm? Nagasaki wrote
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Checking on a couple of sample cameras I see that 5Mp is 2592 x 1944 and an 8MP camera is 3264 x 2448 so all things being equal a 2592 x 1944 crop from an 8Mp camaera will have the same detail as a 5Mp camera. That's not giving you anything near a 10x zoom from a 3x zoom camera although x times zooms are fairly meaningless until you know where they start and end. For example a 50 - 500 mm zoom is a 10x zoom so is a 20-200 but they're very different lenses.

Also as I said it depends on all things being equal not all lenses are the same quality so a 5Mp camera may give far better results than an 8Mp camera. The other issue is that when it comes to MP more isn't always better, crowding 8Mp onto the same size sensor as 5Mp sometimes the result is a poorer quality sensor.

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Old Mar 21, 2006, 3:31 AM   #7
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Well in 35mm a 50mm lens has approximately the same field of view as the human eye. So a 35-350 zoom would give a moderate wide angle view at 35mm and a magnification of approximately 7 times what you would see with the naked eye at 350mm. How much actual detail you get in the image depends on the quality of the lens and sensor andan 8Mp camera would not necessarily produce better results than a 5Mp camera. It's well worth reading the reviews on this site and comparing the sample shots before buying.
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