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Bayer Interpolation — Does Your Camera Really Have The Quoted Resolution?

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%.

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7 comments… add one
  • O Dec 9, 2011 @ 5:45

    Well Shivanand, I disagree with Mama’s tone but the substance is correct. The Bayer Filter is 50% green, 25% red, and 25% blue. Now, what makes vertical AND horizontal resolution 1/3 each? Even IF the colors had equal share of 33.3% it would mean that 1/3 of the cesor area is dedicated to each color, so the unenterpolated resolution would be 1/3 overall – not in each direction. read more here: http://en.wikipedia.org/wiki/Bayer_filter

  • Shivanand Sharma Dec 9, 2011 @ 13:45

    Cool. I stand corrected.

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