It’s the biggest scam of the camera world. One that has been propagated through extensive marketing and consumer ignorance. And one that irks me to no end. I recently bought a Canon 5D Mark II, and the first thing anyone who sees it asks: “How many megapixels it that?”. My answer of “21″ causes much eye popping glee and a “Wow, that must be a good camera” as I inwardly roll my eyes.
Don’t get me wrong! I wholeheartedly agree. The Mark II is a great camera. But not because of its megapixel count. In fact, a lot of you might be surprised to hear that even though the Mark II supports up to 21MP, I usually set the output mode to sRAW which is just 10MP. Recoiling in horror yet? Read on.
Let me start off with an analogy. There was a time when a computer’s clock speed was all the rage. Manufacturers kept touting higher and higher gigahertz. But we all learned to look beyond that. A new laptop might have an insanely high processor speed, but if its RAM or bus (the circuit that connects processor to everything else) is slow, it will just keep the computer from high performance. Similarly, if a car has tricked out horsepower rating but a suspension that causes the thing to shake at high speeds, then you can’t really go that fast with it *cough* American cars *cough*.
In the same vein, while Megapixels are just one metric for gauging a camera’s performance, simply pumping up pixel counts does not necessarily mean a better camera. In fact, in some cases, it makes for a worse camera.
For simplicity, we’ll use an analogy. Lets think of a camera’s image sensor as an array of buckets. When the shutter opens, light comes in, it falls into the buckets, and the camera then counts the different colors in each of the buckets to produce an image. As you might have already guessed, each bucket represents a pixel. A 10MP camera would have 10 million of these buckets, all condensed into an area the size of a letter key on your keyboard.
Because of the escalating megapixel war, manufacturers have been cramming more and more of these buckets into the same sensor size (because image sensors are expensive). This means smaller buckets and hence smaller areas to capture light. Of course, these light detectors in the buckets are not perfect. That is because they are converting an analog signal (light intensity) to a digital signal (a pixel, defined by 16 bits of color). Sometimes they will mis-count the amount of the different colors of light.
In big buckets this is not a problem, because even if the camera counts one more or one less, the mistake is relatively small. For example, a bucket has 10 red balls and the camera counts only 9. Big deal, only a 10% error. On the other hand, smaller buckets capture less light, and hence are more error prone. A bucket with 2 red balls counted as 3 means a 50% error! This results in noise. It’s the annoying dots that appear in your images making everything look grainy.
Simply put, increasing the number of Megapixels on your camera, without advances in noise reduction technology, increases the noise on your pictures, reducing image quality. In fact, industry experts say that a point & shoot camera gains little performance beyond 6-8MP. For SLRs, since they have a larger sensors, the limit is somewhere in the 30-40MP range.
And it ended sometime early this decade. But it happened very quietly. In fact, some camera marketers don’t seem to know this either. They still want you to believe that gazillion megapixel camera is what you should buy. The truth of the matter, however, is that unless you want to make (insanely) large prints of your images, you don’t gain much beyond 12MP.
Make smarter decisions when buying your next camera. Drop the megapixel hype and concentrate on what really matters. Look for the image quality. Look for noise performance. Wider angled. Zooms (optical). Sensor size. Shutter lag. Image stabilization.
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