Saturday, September 20, 2008

Megapixels Begone (Comparative Metrics That Won't Go Away)

When you see a digital camera for sale, the first thing listed is usually the megapixel count: the camera’s maximum resolution in millions of pixels.

It’s the most important attribute because more megapixels means better pictures, right? With today’s digital point-and-shoot cameras, the answer is somewhere between “not necessarily” and “no.”

I noticed this issue last year when shopping for a point-and-shoot digital camera. Various roads led to the Fuji FinePix F30/31 series, which Digital Photography Review described like so:

In the fast-moving, ‘bigger better faster’ world of the digital compact the Fujifilm FinePix F30 will be one of the rare few that are remembered after they have gone (the nearest this throwaway business gets to a ‘classic’). The reason this unassuming, blocky little camera stands out from the scores of other cameras launched last year - and why it has a mantelpiece covered in industry awards - is simple; image quality, or more specifically, high ISO performance. The F30’s low light capabilities come from a combination of clever technology (Super CCD and Real Photo Processor) and a ‘swimming against the tide’ attitude to specification, which means a bigger sensor with fewer pixels. The F30 also, against all the odds, actually sold pretty well, going against the conventional wisdom that consumers buy on pixel counts alone. Although it has its share of faults the F30 became the benchmark by which all compact cameras in the 6-8 megapixel sector were judged.

But at the time I was shopping, Fuji had moved on to the F50 series. Here is what DP Review had to say about it:

Fujifilm has finally caved under the pressure and joined the mainstream with the F50fd, doubling the F30/F31fd’s pixel count to squeeze a whopping 12 megapixel on the tiny 1/1.6in sensor....

The good news is that - forgetting the F31fd for a moment - the F50fd is an excellent point and shoot camera that deserves a place near the top of its class. Sure, Fujifilm listened to its marketing department and installed a 12MP sensor, but the F50fd’s high ISO performance is still surprisingly good. On a per-pixel basis it is certainly not on a par with its predecessor but on an output level, i.e. on a print of the same size or a computer monitor the difference isn’t huge. Of course it would have been a lot better with 8 million larger pixels, but I’m afraid even Fujifilm isn’t brave enough to launch a premium compact camera so ‘under powered’ in today’s market....

The replacement of the F31fd means the end of the line for a sensor that over four generations of Fujifilm compact cameras has shown that there is an alternative to pointless megapixel increases and noisy results at anything over base ISO. Whilst the F50fd still has a lead over its conventional CCD competitors that advantage has been cut down to little more than a whisker, and this is a regrettable and slightly depressing indication of where the compact camera manufacturers’ priorities lie.

In other words, the F50fd was among the best point-and-shoot cameras of its time for image quality. However, the cameras of its time all had taken the same step backward by squeezing too many pixels into a given size of sensor. Thus, all the newer models were inferior to the F30’s image quality, especially in less than perfect lighting.

So what happened? Over to photography blogger Micah Marty, from late 2007:

Here’s a first: a digital camera that has appreciated in value. That’s right: if you had bought a truck full of new Fuji F30/31 cameras and just parked it in a warehouse for a year before selling them, you’d have no problem paying those holiday bills. Contrary to conventional wisdom (“Digital cameras always decrease in value when the successor model is introduced”) those two discontinued Fujis have almost doubled in value since they were current.

This happened, of course, because a few months ago Fuji decided to forgo its primary edge over the competition (“Less noise”) in favor of being more like the competition (“More megapixels!”). As a result, discontinued-but-new F30s that once could be bought new for $230–260 are now up as high as $400 on eBay, while the discontinued-but-new F31s that once could be bought new for $250–275 are now approaching the $500 mark on the same auction site. Those two cameras each have six megapixels; their shiny new successor (the F50), with twice as many megapixels but also more noise—and, by the way, a shorter-lived battery—currently is selling for $228 new at B&H.

The persistence of megapixels as digital cameras’ key advertised feature is a case study in a particular flavor of numbers abuse: the comparative metric that won’t go away. Such metrics typically made sense at some point in the past but, as with megapixels, outlived their usefulness as descriptions of quality. Yet they remain because, like kids studying to the test rather than learning the subject, manufacturers keep designing products to excel at the metric—after all, it’s what the market (thinks it) wants.

Having designed their cameras for more megapixels, the manufacturers are then obliged to tout their new cameras’ excellence on that metric, thereby reinforcing the metric in consumers’ minds.

It’s a vicious cycle, and the fate of the Fuji FinePix line demonstrates how hard it is to stop.

[Sidenote: Technically, the megapixels issue is not about an absolute limit. It’s about the number of pixels in relation to the size of the sensor. Thus, digital SLRs (the pro-looking cameras with swappable lenses) can get better quality from, say, 12 megapixels rather than 8 megapixels because the 12-megapixel sensor is typically larger in the digital SLR. In contrast, point-and-shoot cameras’ smaller bodies resist larger sensors, so manufacturers have packed more pixels into the same sensor size—despite the evidence that, above 6 megapixels, it hurts more than helps. For more details, see Image Engineering’s 6 Megapixel site, a public-interest plea in the name of 6-megapixel point-and-shoot cameras.]

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