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Old Feb 5, 2006, 12:51 PM   #1
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Three years ago I bought a Nikon Coolpix 2500 with 2 megapixels. Last month, for half the price, my son bought a Canon Powershot A95 with 5 megapixels. I thought it would be interesting to take some photos with both and make comparisons.

Usually the photos made by both cameras looked just as good when viewed at ‘fit to screen' size. But when I zoomed in on parts of the photos at 100% or greater the Canon photos were superior. In the Nikon photos some straight lines and flat planes became untidy, but were still clear in the equivalent Canon photo at the same magnification.

But there was one important exception to this rule: photos taken in art galleries without flash or tripod. I do this a lot; it's permitted in this country. Of course camera shake is a problem. If 40% of my photos are reasonably sharp I'm happy to discard the rest. I found by experiment that in order to achieve this kind of hit-rate I had to set the Nikon and the Canon to ISO400 sensitivity.

Used at ISO400 under these conditions most photos contained some degree of noise (ie picture breaking up into dots, often of irrelevant colours; breakup into irrelevant regular shapes). Although just about acceptable, at ‘fit to screen' size, there was more noise apparent in the Canon photos. As soon as I zoomed in, I could see that the Canon photos were much noisier than the Nikon.

From the above I drew the following tentative conclusions:
  • In general, other things being equal, the more megapixels a digital camera has, the HIGHER the quality of the image - provided the camera is not used at ISO400 or higher. [/*]
  • But when used at ISO400 or higher, in general, other things being equal, the more megapixels a digital camera has, the LOWER the quality of the image.[/*]
I'd be really grateful if anyone could tell me if these conclusions make sense. If they do, then I can reason a bit further. But first I'd like to know what you think of the above.
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Old Feb 5, 2006, 3:29 PM   #2
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The conclusions make sense possibly, but just for these two cameras under those specific conditions. It is impossible to make such a blanket comment from a sample size of just two cameras. There is much more to the equation. One of the biggest issues influencing noise is just getting proper exposure. Nailing the exposure will go a long way in reducing the amount of noise...underexposure creates a lot of noise, and its very easy to underexpose under the conditions you mention. Different cameras use different processing algorithims, levels of sharpening, color rendering etc, all of which can also influence noise and picture quality. You also have to consider lenses, maximum aperature, etc. I guess the key phrase is all things being equal, but often when comparing cameras, all things are never equal.
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