Busting the Megapixel Myth

So the Average Joe just bought another digital camera. He saw the fourteen megapixels advertised for a compact digital, and immediately emptied his wallet. Had he known a little bit better, he could have bought something more worthy. Though if you are thinking that he could have saved some money too, that does not happen in the digital camera world. Good things come for a price, and his wallet would have been emptied regardless. However, there is one irrefutable fact. That there are worthy products available to suit wallets of all sizes.

The digital camera marketplace is a tough place to be at for the customer. The multitude of manufacturers and their countless products do not make for a customer centric market where the customer has a lot of choice. It only goes on to confuse a prospective customer so much that he more often than not ends up getting a product that does not serve the purpose to begin with. All this happens because of numbers. Numbers are a very big and very strong part of all advertising. The general perception is that if any product sports a bigger number than some other competing product, its gotta be good. And as a result, the advertisements focus primarily on numbers. And imagine the impact that a number that runs into the millions has on a customer and this is where the megapixels come into play.

Back in good old film days, we just had film frame sizes. There was large format film for the serious professionals and the nuts, there was medium format film for the smart professionals and the enthusiasts. And there was 35mm film for professionals whose job demanded extreme flexibility. And the same 35mm film was also for the rest of us. For years, nay decades the 35mm film ruled all family, amateur and photojournalist photography. Film was just film, an analog medium with no specific method to calculate the resolution in terms of megapixels.

Then came along the digital age, and as with all things digital, there were numbers attached to the size of the image that you could make with a camera. Starting off in the kilopixel domain, over time these reached the megapixel domain. And then began the megapixel wars that still continue to the day.

Before we delve deeper into megapixels, let us understand what a pixel is - a picture element. One pixel represents a colored (and in olden days a grayscale or even a monochrome) dot. And the entire image is made of a huge number of these pixels. Whether it is your computer monitor, or a digital camera photograph, or even a digital print - all are made of thousands or millions of these pixels. And if ya get together a million of these pixels together, it makes for a million pixels - or a megapixel. And if the total numbers of pixels that are contained in the output file from your digital camera is about ten million, the manufacturer will proudly call it a ten megapixel camera. Now these eight million pixels are often arranged in some accepted aspect ratio form factor - such as 3:2 (the classic 35mm film full frame) or the 4:3 or 5:4 ratios that some other people prefer. And thus those ten million pixels that are crammed onto the digital imaging sensor of the camera would be arranged into a 3650pixel by 2750pixel grid for a 4:3 ratio, or some grid with other vital stats for different aspect ratios.

Now there might be a six megapixel camera, an eight megapixel camera, a ten megapixel camera, a twelve megapixel camera, a fourteen megapixel camera and even a twenty-one megapixel camera. Now, the Average Joe who is doped heavily on the camera advertising will immediately pick the twenty-one megapixel one, see the price & have a near heart attack, then pick the fourteen megapixel compact and get going, laughing on all those who are lining up for the larger in size and much costlier camera that has just "twelve" megapixels. Little does the Average Joe know that Not all pixels are created equal. Heck he perhaps doesn't even know that the six megapixel camera that he did not even look at might net him much better pictures.

All this megapixel craze has significance perhaps only in the digital age. Back in the film days, the primary factor was what film were you using, and equally important was the quality of the glass. And more importantly, you just took the photographs, and then got them developed on a decent sized paper. You did not blow them up to insane sizes of pixel to pixel magnification on your 24 inch monitors. And even if you wanted to use those images on the computer monitors, would you actually put them at pixel to pixel zoom, or fit to the screen. And in fitting to the screen, there is not a single monitor available on the market that has more resolution than the cheapest camera available on the market.

The camera was practically not a big factor in image quality, unless somehow a bad camera messed up with some of the exposure parameters and killed your photograph, or exposed the film from some stray light that entered into the camera from somewhere that it shouldn't have. But in the digital age, they messed with all that. What with the image sensor being a part of the camera and that they created all sorts of smaller sensors to enable having smaller optics and as a result more and more compact cameras. What they effectively did was that the physical size of the pixel became smaller and smaller to allow for small sensors and large resolutions. And with that, while the continuously improving technology allowed for each increased resolution (i.e. smaller pixels) to not get completely messed up, the small sensor compacts can not at all match the picture quality pixel for pixel and thus of the photographs taken by the larger sensor DLSRs. Heck sometime what may even happen is that a lower resolution compact may have a better image quality than a higher resolution one because the megapixel count resulted in pixels so messed up that well, the entire image is messed up.

To understand that more clearly, we might have to go a bit deeper into how the digital camera image sensor works. Each one of those millions of pixels of the digital sensor is a photosensitive site, and as light falls on it, it generates a signal which is stored into the memory as the photograph. Of-course there are things like micro-lenses and color filters and Bayer filters are involved, but that is a discussion for another day. So if you cram a lot of megapixels on a small sensor, each pixel gets smaller and smaller, and thus it has lesser and lesser area for light photons to hit the pixel and as a result the response of the sensor to low light takes a solid hit, as does the per pixel clarity due to a variety of factors including diffraction.

Now suppose that you have two cameras, both of the same resolution, say ten megs. One is a compact with a super shrunk sensor, the other is a APS-C SLR. The ratio of the size of each pixel sites on those cameras is perhaps close to ten, or even more than that - means that atleast 10 times more light goes into making each pixel of even an entry level SLR than a compact. Couple that with the larger pixels that require less lens resolution per unit glass area, and it means that the flaws in glass are not so pronounced. What finally results out of the SLR sensor is a picture that has much more per pixel detail and sharpness, and hence the phrase "Not all Pixels are created equal".

So the next time you go out to empty your wallet at the cameras store at the mall, just think for a while what you actually, and how big prints would you actually be making, or for that matter, even the resolution of your computer monitor. Just don't go out and buy the highest megapixel pusher you can, take a look at what kinda pixels it spews.