Monday, 1 August 2011

Mine's bigger than yours . . .the Megapixel Myth

Well, I've taken the last photographs of the Australian National Indoor Cricket Championships, now there's just a few days of editing and publishing photos on the website to go (read my posts on the Australian National Indoor Cricket Championships and see photos of the four Australian Champion teams HERE).

I've been asked a lot this past week about photographing sport, camera gear, websites, selling photographs, how to get started in photography, and the most asked question: "how many megapixels is that camera?".

Okay, in this post I'm going to try to address that last question--well, more specifically, I'm going to address why that last question is totally meaningless. But if you know all about the Megapixel Myth, perhaps you'd like to put the kettle on and have a cuppa while I carry on.

Not long after buying my Nikon D700, I had to concentrate and specifically remember exactly how many megapixels my camera had. Not because it's all that important (trust me, it's NOT ALL THAT IMPORTANT), but because I got asked it so many bloody times and people thought I was lying when I replied "I don't know" and/or "number of megapixels isn't important". I still say that, but I then add the number to make folk happier. There are a host or reasons why the number of Megapixels is not important. I'll concentrate on the most obvious.

Comparing number of megapixels in different cameras is about as helpful as comparing number of seats in different cars. It doesn't help determine which camera/car is "better" than another camera/car. Let me explain: car A is better than car B because car A has 6 seats, whereas car B only has 4. So car A has to be better, right? Okay, what if car A has those 6 seats crammed into a car as big as a tiny little BMW Mini, and car B has its 4 seats in a body as big as a Land Rover? As far as comfort for its passengers, which car is "best"? And what about road-holding? Speed? Cornering ability? Fuel economy? The number of seats tells you pretty well nothing other than . . . the number of seats.

So it is for megapixels. Please note, the following discussion takes some small liberties with exact scientific definitions, but it is accurate, so please, no scientific arguments on the exact nature of such matters.

Pixels are tiny little electronic receptors that "see" light. Individually they are just a dot in a photo, but put them all together and you have your photograph. Aha I hear you cry, so the more of them you have, the more detail in a photograph. Well no, not quite.

Pixels are located on what is known as a "sensor". For those who know what I'm talking about, the sensor can be considered the same as a piece of "film". So 5 megapixels is 5 million pixels (no, "mega" doesn't just mean "big", technically it means "million"). Sensors come in a wide range of sizes . . . you can see where this is leading, right? Good, read on.

To accurately record the light they "see", pixels need to be a very particular and exact shape. The smaller they are, the harder it is to make and arrange them accurately. The more you fit together on a sensor, the smaller they become. It reaches a point where they become so small that they lose some of their accuracy and do not give you as sharply detailed a photo.

Another thing about pixels is that each and every one of them is connected electronically to the camera's processor. Like all electronic devices, pixels give off electronic "interference", and in turn are affected by electronic interference of nearby appliances. Operate your power tools next to your television and you may just see what that interference looks like on your tv screen.

With pixels, if they are too close together, they too suffer from the interference generated by their neighbours. In digital cameras, that "interference" shows itself as "noise" . . . take a photo in very dark conditions and you will see ugly blotches of colour especially in dark areas of the photo. This is "noise", and is caused by the electrical interference of one pixel on another. So again, if you have too many pixels on too small a sensor, you will suffer from extreme noise on your photos, making them almost useless.

Back to the two cameras I used to photograph the indoor cricket this week, a Nikon D700 and a Nikon D3s. Both are "only" 12.1 Megapixels. On hearing this, I have had many people look aghast and snootily inform me that their small point-and-shoot has 20 Megapixels. Guess what they mean is that their camera is "better" than mine. And in some ways of course it is: you can put a small camera in your pocket, you can't hide mine in a pillowcase; small cameras weigh nothing, mine weighs a ton; small cameras are easily smuggled into concerts, mine has been smuggled in many times but it necessitates carrying a huge jacket (get strange looks in the middle of summer) and wearing a very loose shirt; for pick-up-and-take-a-snap photography, small cameras do a fantastic job. And large sensors are extremely expensive to make, so cameras with small sensors are much cheaper. But the smaller cameras have one major drawback: they have a tiny, tiny sensor. So all those zillions of pixels they have are crammed onto a sensor sometimes smaller than your fingernail. Whereas my "only" 12 megapixels are comfortably spread out over a sensor measuring a whopping 36 x 24 mm. This means two very important things: the pixels on my camera are much, much bigger (less pixels on a much larger sensor) and therefore more precisely accurate in construction, and the pixels on my camera are much further away from their neighbours (again, less pixels on a much larger sensor) leading to a dramatic lessening of electrical interference (and therefore much less "noise"). So the 12 million relatively huge pixels on a relatively huge, HUGE sensor will give a much more detailed, noise-free image than the same amount (or more) of Megapixels on a smaller (sometimes tiny) sensor. Even with other professional-quality Digital SLR cameras, the number of Megapixels in itself is not a basis for any meaningful comparison between cameras. A $10,000 24 megapixel Nikon or Canon will not shoot as "clean" in low light as either of the two 12.1 megapixel cameras I used at the cricket (which is exactly why I used those particular cameras).

I shot the indoor cricket at ISO 5000, which allowed me to shoot at shutter-speeds of between 1/250 to 1/1000th of a second. Even that $10,000 24 megapixel camera cannot match the outstanding lack of noise and accurate details at ISO 5000 as these two Nikon cameras . . . even with their "only" 12.1 megapixels. Of course, for some different uses the 24 megapixel cameras would be the better choice, and for others, the small point-and-shoot would be perfect -- but it's the use you are putting a camera to that defines its suitability and whether or not it is "the best" or "better", NOT the number of Megapixels.

So the next time you hear someone ask "how many megapixels does your camera have", you might mentally add "what size sensor are they crammed onto?" . . . .

Like I said, number of Megapixels is not all that important, and should NEVER be used to judge one camera against another.

Unfortunately the fact that most punters still think camera A with 5 megapixels is better than camera B with only 4.5 megapixels is proof that advertising works--even if it's actually sprouting bulldust.

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