What if someone told you that your 10 megapixel camera only has the effective resolution of 1 megapixels? Sounds like a scam – only that this is technical in nature. And at the end only those with a keen eye for details realize the difference. I’m over-simplifying but the topic warrants it.
The resolution is measured by the number of pixels on the screen. This can be the screen of a TV or a computer monitor or the camera sensor. Every pixel contains three sub-pixel components meant to handle three primary colors red, blue and green. So if you use a magnifier to see the detail on your computer’s LCD monitor, you’ll notice the three sections red, green and blue. The resultant color at the pixel is determined by the combined intensity of these three components. So for example when the red and green components are illuminated the resultant color is yellow. When all three are illuminated you get white.
However camera manufacturers play it smart. They simply quote the total resolution taking into count these sub-component pixels. So whereas it is supposed to be one pixel (with the three sub-components red, green and blue) they quote three pixels. In effect this means that your actual camera resolution has been blown up by a multiple of three and quoted on the specs. However only 1/3rd of this quoted resolution is the actual effective resolution.
How then do you still get the images at the quoted resolution? Here the Bayer Interpolation comes into play. Using an algorithm the missing pixels are artificially recreated to result in the quoted resolution. This is one reason why images resized and shrunk by a factor of three look more pleasing and natural to the human eye.
Bayer Interpolation is something that digital cameras can’t do without till the manufacturers stop quoting the multiplied resolution and quote the actual resolution like the computer LCD manufacturers. So we are down to the moral of the story – shoot at the cameras maximum resolution. When you are done, reduce your image to a smaller size. This results in the loss of the artifacts and the synthetic pixels while raising the overall density of the picture. But this is all when you have it at the back of your mind that there’s something called Bayer Interpolation happening and that you are loosing on the quality of the image (more on the factors affecting the image quality here). That said the algorithm is still smart to trick the naked human eye of course unless you are viewing the picture at 100%.
No, I’m not agreeing with the factor of 1/9th at all. I’m saying that the basic resolution of the sensor is just about what you would figure given the quoted pixel density accounting for the sensor size (FX, DX, or whatever). I add that one also has to consider the presence of any anti-aliasing filter, when those are built in, as in the case of most DSLRs. As to my blog, anyone can take it or leave it. I get to publish what I want there, including all kinds of math and figures that don’t work as comments.