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Do our cameras have too many megapixels?

image sensor
Devin Coldewey / msnbc.com

When buying a camera, one of the few things the average consumer reliably looks at is the megapixel count, a measure that has been rising steadily for years. But are those megapixels really making for a better picture? Or could they in fact be doing the opposite?

On Thursday, Nikon announced a new entry-level camera for photographers perhaps buying their first DSLR. It has a nice new screen, a wide variety of lenses, and, surprisingly, a whopping 24 megapixels.

Devin Coldewey / msnbc.com

Now, that's a lot of pixels -- more, in fact, than many professional-level cameras out there. And while they're certainly useful for some things, like keeping a nice big image after cropping down a shot, that many pixels packed onto a modestly sized sensor also has some drawbacks.

For one thing, the kit lens that ships with the D3200 probably isn't the greatest, and many new photographers won't think to pick up a different one. It's not that it's a bad lens -- but no lens is perfect, and when you have that many megapixels, you can really start spotting the flaws, like the blurry areas at the edges or color distortion at the edges of bright objects.

But the D3200 is still a good camera with a good lens. The same can't usually be said for the lens and sensor in, say, a point-and-shoot camera or smartphone. Imaging companies like Omnivision and Sony are packing more and more megapixels onto tinier and tinier sensors, and as an engineering feat it's impressive, but it probably isn't making for better pictures.

The problem is that, when taking a photo, you need a clear image and plenty of light. Big, "fast" lenses gather lots of light and transmit it efficiently and with great clarity to the sensor, because compared to the size of the lens, small optical flaws and slight misalignments of elements don't produce that much of an effect. But imagine in a tiny camera system like one found in a smartphone. Everything is so small that even a tiny flaw in the lens have a major effect on the image.

Devin Coldewey / msnbc.com

And it's more than just that. Because the light-sensitive pixels that make up sensors are so small on these tiny sensors, the image coming through the lens needs to be even more clear than on bigger cameras! Think of it this way: you print a big photo at 8x10 inches, and it has a certain amount of detail. Now say you want to print that same exact amount of detail onto a picture the size of your thumbnail. Imagine how precise the printer would have to be!

An image that's high in megapixels can still be low in detail. It could be out of focus, for one thing, but even if it's "in focus," the lens may not ever be able to resolve a clear enough image to give you your money's worth out of those 20 megapixels.

Lastly, there are other things companies could be doing with those pixels. Instead of making the pixels smaller and packing more onto the same size sensor, they could make them bigger and more sensitive, improving the camera's performance in low light. Or they could change the way the camera detects and interprets color, to give a more vibrant and reliable look.

Apple

The iPhone 4S's camera is a good example of how improving the camera means more than just upping the megapixels. It uses a new and better way of organizing the image sensor and has a genuinely decent lens on it -- and those contribute far more to the quality of the camera than the extra megapixels. Likewise, Fujifilm's latest pro camera doesn't beat the competition on sheer pixel count, but claims better image quality due to a more advanced way of organizing the individual blue, red, and green pixels on the sensor.

More megapixels isn't inherently a bad thing. But it can be, and there are trade-offs every photographer should be aware of, especially if they are thinking of buying a new camera.

Devin Coldewey is a contributing writer for msnbc.com. His personal website is coldewey.cc .