Charade said:
I respectfully disagree that the number of megapixels has little to do with the overall image quality. Several brands (like Canon) make 3.2, 4, and 5 megapixel versions of essentially the same camera. Same optics, same image processor with the major differences being in the feature set.
If you were to make a 4x6 print of the same image from each of these similar models, most people would be able to see a difference. May not as much of a difference between the 3.2 and 4, but definitely between the 3.2 and 5. Especially with images like landscapes and scenes where the main subject doesn't take a up a large portion of the frame.
The problem is that most people don't care that much or don't know what to look for.
I will agree that *the* major component that contributes to image quality is the lens followed by the image sensor.
I'm not saying that the number of megapixels is the most important factor because I know that my 4 year old 2.1mp Oly 2100 (10x optical stabilized lens) takes much better pictures than some low end (mainly no name) cameras with many more megapixels.
The math does not support your contention
A tiny linear resolution increase results in a huge total pixel increase, since the total pixel count varies as the total area of the image, which varies as the square of the linear resolution. In other words, an almost invisible 40% increase in the number of pixels in any one direction results in a doubling of the total number of pixels in the image.
One needs about a doubling of linear resolution or film size to make an obvious improvement. This is the same as a quadrupling of megapixels. A simple doubling of megapixels, even if all else remained the same, is very subtle. The factors that matter, like color and sharpening algorithms, are far more significant.
To figure out how big a print you can make before you start to lose sharpness there is simple formula:
Long print dimension in inches = 4 x (square root of megapixels)
The biggest print you can make without losing sharpness at normal viewing distances is is 6 x 8."
Of course you can print much bigger, since sharpness isn't as important in color as most people worry. You can get great results from a 6MP camera at 20 x 30" if you want, since normal people view big images from further away.
Don't worry too much about this, since sharpness is not as important in color as it is in B/W. I have a photographer friend that makes 12 x 18" color prints all the time from 3 MP cameras and they look great.
I agree that plently of lower MP cameras can produce better photos than poorer quality cameras with higher MP's