High Megapixel Compact Digicams May Be Worse than We Thought

Dan Knight - 2008.02.21

Last month we looked at the megapixel myth. As we noted then, "in the rush to market megapixels, images can actually be worse with a high megapixel camera than from a lower megapixel one."

The sad truth is that it's worse than we thought.

Mason Resnick of Adorama has exposed another issue caused by an unhealthy fixation on megapixels: As compact digicams include more and more megapixels on their tiny sensors, something has to give. In Stop the Megapixel Madness!, he says,

"...each pixel has its own microscopic lens, and each lens is separated by a microns-wide wall, or septum, to prevent light from falling from one pixel into the next and thereby reducing image quality . . . to make room for eight, nine, or (heaven help us, again) ten million pixels, those septums get either unusably thin, or are removed altogether."

The result of removing the septum? Spillover from one pixel another, which can cause fuzziness and increase noise (the digital equivalent of film grain).

As we've said before, 3 megapixels is all you need for a great 5x7, and most people can't tell the difference between an 8x10 from a 3 MP image or a 6 MP one. A 6 MP digital will easily give you a 12x18 print that looks very sharp indeed.

So why the fixation with megapixels? It's not quality, it's marketing. If 3 MP is better than 1.3 MP, and 6 MP is better than 4 MP, then 12 MP must be even better.

While it's true that more megapixels means better images that can be printed even larger on digital single lens reflex (DSLR) cameras, that's not always the case with compact digital cameras. Beyond a certain point, the small imagers with their increasingly small individual pixel sensor get small enough that digital noise becomes a factor. Your photos may have more pixels, but they are also likely to have a lot more grain.

Make the pixels small enough, and the septum (the dividers between the individual sensors), no matter how thin you make it, ends up cutting off some light, further increasing grain. The solution? For some manufacturers, it's removing the septum, which means that light can spill over to adjacent pixels.

The result is a lower contrast, grainier, fuzzier image, as Adorama clearly shows on its website. Too many megapixels in a compact digicam can mean worse images, not the better ones you would expect. And none of the manufacturers are going to make a point of telling you if they don't have a septum on their imager.

Don't believe it? Check out the comparison images that Adorama has posted (reduced even further below). Even when greatly reduced to 0.15 MP for use on the Web, those shot with an 8 MP DSLR look gorgeous, as everyone would expect. Those shot with an 8 MP compact camera look horrid: low contrast, washed out colors, more grain, and blurring of details. And there's nothing you can do in Photoshop to fix those problems.

You can, however, make matters even worse by shooting at a higher ISO setting. Again, it's something DSLRs can do well with their larger sensors, but as far as compacts go, it's going to further increase noise and graininess in your images.

DSLR vs. Compact
Comparison of 8 MP DSLR vs. 8 MP compact (reduced from Adorama website)

As Resnick notes, "You may be able to make big blow-ups with your 12MP compact, but they won't look as good as manufacturers want you to believe."

Don't buy a camera based on specs. All imagers are not created equal. All lenses are not created equal. And all 8 MP images are not created equal, and 8 MP may be more than you need. Kudos to Adorama, a camera retailer, for pointing out the truth.

Look at the images the camera creates. That's the true test, not the number of megapixels in its images. LEM

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