Many, from experts to engineers agree that megapixel count has been promoted (by camera stores and camera companies) as a misleading marketing gimmick for years. My argument—and my test—maintains that 5 or 6 megapixels is plenty for enlargements up to, say, 16-by-24 inch posters.
There were still a few naysayers who don't believe the results. This one was typical: "Why do you insist in calling it a pixel myth? Other things being equal, 8 megapixels DOES give a higher quality than 5; you just can't see it."
(Um, dude? If you can't see any difference, then it's not higher quality.)
In this Article, I'd like to expound upon a couple of points that my print column didn't have room for.
First, one reason WHY a few more megapixels don't produce any visual differences in the print.
Let me tease you first with this question: How much bigger can I print a 10-megapixel photo than a 5-megapixel photo?
Most people answer, "twice as big" or even "four times as big."
But they're wrong. In fact, doubling the megapixels of a photo actually lets you add only 20 percent more area to each edge.
Here's the math. A 5-megapixel photo might measure 1944 x 2592 pixels. When printed at, say, 180 dots per inch, that's about 11 by 14 inches.
A 10-megapixel photo (2736 x 3648 pixels), meanwhile, yields a 180-dpi print that's about 15 by 20 inches—under three inches more on each margin!
Upping the resolution by even smaller amounts (from 5 to 7 megapixels, for example) produces an even tinier difference—too small to bother with.
Meanwhile, cramming more pixels onto a camera's sensor can actually LOWER the quality of the photo. A former Kodak manager wrote to explain it this way: "Too many megapixels can actually impair a camera's performance. For example, the typical sensor in a consumer camera is 0.5-0.7 inches. The more millions of pixels, the smaller each pixel must be—and the smaller the pixel, the less light-gathering efficiency it has, and the worse the camera performs in low-light or stop-action shots."
Now then: At the end of the Article, I pointed out that megapixels have become a handy crutch for consumers shopping for a camera. They'd come to rely on it as a letter grade that made comparison shopping easy—and camera makers exploited this fact. "Well, heck, this one has 10 megapixels! That's a lot better than this 6-megapixel model!"
But a million factors are far more important than the megapixels. The question is: Can we come up with a new one-digit crutch? Can we propose a more meaningful comparison factor?
Lots of you said yes, the sensor size is far more important. After all, it's undisputed that a 6-megapixel Nikon D40 digital S.L.R. takes better pictures than a 10-megapixel shirt-pocket camera, because its sensor is relatively gigantic. Its individual pixel sensors can be larger and soak in more light, even if there are fewer of them.
Unfortunately, the camera makers and salespeople aren't going to help you out here. You're not going to see starbursts in the ads saying, "3/4-INCH SENSOR"! But you should.
If you can do the math—you can find sensor sizes reported at camera-review Web sites, like steves-digicams.com, dpreview.com, and dcresource.com—you'll be well rewarded. There are a million factors to consider when you buy a camera, but this one's a fairly good predictor of picture quality.
"Incidentally, where the megapixel myth really goes berserk is with camera phones. Limited real estate forces the camera modules to be tiny, which means that the pixels get tiny--well under 2 microns--when the marketing people force the engineers to increase the pixel counts, because megapixels sell. Unfortunately, tiny pixels are noisy, work poorly in low light, and may not be utilized due to a physical phenomenon called lens diffraction. Engineers are well aware of the problems, and they keep butting heads with the marketing people.
There were still a few naysayers who don't believe the results. This one was typical: "Why do you insist in calling it a pixel myth? Other things being equal, 8 megapixels DOES give a higher quality than 5; you just can't see it."
(Um, dude? If you can't see any difference, then it's not higher quality.)
In this Article, I'd like to expound upon a couple of points that my print column didn't have room for.
First, one reason WHY a few more megapixels don't produce any visual differences in the print.
Let me tease you first with this question: How much bigger can I print a 10-megapixel photo than a 5-megapixel photo?
Most people answer, "twice as big" or even "four times as big."
But they're wrong. In fact, doubling the megapixels of a photo actually lets you add only 20 percent more area to each edge.
Here's the math. A 5-megapixel photo might measure 1944 x 2592 pixels. When printed at, say, 180 dots per inch, that's about 11 by 14 inches.
A 10-megapixel photo (2736 x 3648 pixels), meanwhile, yields a 180-dpi print that's about 15 by 20 inches—under three inches more on each margin!
Upping the resolution by even smaller amounts (from 5 to 7 megapixels, for example) produces an even tinier difference—too small to bother with.
Meanwhile, cramming more pixels onto a camera's sensor can actually LOWER the quality of the photo. A former Kodak manager wrote to explain it this way: "Too many megapixels can actually impair a camera's performance. For example, the typical sensor in a consumer camera is 0.5-0.7 inches. The more millions of pixels, the smaller each pixel must be—and the smaller the pixel, the less light-gathering efficiency it has, and the worse the camera performs in low-light or stop-action shots."
Now then: At the end of the Article, I pointed out that megapixels have become a handy crutch for consumers shopping for a camera. They'd come to rely on it as a letter grade that made comparison shopping easy—and camera makers exploited this fact. "Well, heck, this one has 10 megapixels! That's a lot better than this 6-megapixel model!"
But a million factors are far more important than the megapixels. The question is: Can we come up with a new one-digit crutch? Can we propose a more meaningful comparison factor?
Lots of you said yes, the sensor size is far more important. After all, it's undisputed that a 6-megapixel Nikon D40 digital S.L.R. takes better pictures than a 10-megapixel shirt-pocket camera, because its sensor is relatively gigantic. Its individual pixel sensors can be larger and soak in more light, even if there are fewer of them.
Unfortunately, the camera makers and salespeople aren't going to help you out here. You're not going to see starbursts in the ads saying, "3/4-INCH SENSOR"! But you should.
If you can do the math—you can find sensor sizes reported at camera-review Web sites, like steves-digicams.com, dpreview.com, and dcresource.com—you'll be well rewarded. There are a million factors to consider when you buy a camera, but this one's a fairly good predictor of picture quality.
"Incidentally, where the megapixel myth really goes berserk is with camera phones. Limited real estate forces the camera modules to be tiny, which means that the pixels get tiny--well under 2 microns--when the marketing people force the engineers to increase the pixel counts, because megapixels sell. Unfortunately, tiny pixels are noisy, work poorly in low light, and may not be utilized due to a physical phenomenon called lens diffraction. Engineers are well aware of the problems, and they keep butting heads with the marketing people.
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