Best Compact Digital Camera: A review of the Canon S90

Ok, let’s get one thing out in the open. The Canon S90 is expensive -- MSRP is $430.  But what we’re sure of is that this is currently the best “pocketable” digital camera on the market, bar none.

The megapixel race: An unfortunate history
For years, digital camera manufacturers have realized that “megapixels” sell.  When the average consumer is faced with a choice between “Model A” at 10 megapixels and “Model B” at 15 megapixels, all else equal, guess which gets chosen?   Camera manufacturers have long known that megapixels are the single most important “spec” for uninformed buyers, so they play the game. Today, point-and-shoots with megapixel counts in the mid-teens are commonplace. But the question is, does image quality rise with the increase in pixel count, as the typical buyer assumes?

Mega Megapixels: More harm than good
It’s true that up to a point, more megapixels will yield higher resolution photos. But as megapixel count increases, overall image quality eventually begins to degrade. To better understand, let’s consider an image sensor of a given size. A typical Canon “Powershot” camera might be equpped with a sensor that’s 0.28 square centimeters in size. A few years ago Canon might have squeezed 6 megapixels into that sensor size. But today, 12 megapixels (or more) might be squeezed into that same sensor – this means that the size of each pixel “site” is half of what it was previously.  And the problem is that, all else equal, smaller pixels are “noisier.”  The image (or “signal”) that the sensor intends to capture is watered down by addition of more random noise than would be the case with a sensor with larger pixel sites. Greater noise causes color, saturation, and contrast to suffer. And perversely, because most digital cameras are designed to combat noise partly by averaging signal across adjacent pixels, even resolution can suffer. 
In low light, the sensor’s noisiness becomes particularly apparent because as less light hits the sensor, our “signal” becomes attenuated, while the level of digital noise stays constant.  A sensor with a poor signal-to-noise ratio is more easily revealed for what it is in low light (where “noise” begins to dominate), than in bright light (where the “signal” dominates over noise).
Wait, I’ve got the solution!
 “Easy,” you say, “since small pixels are noisy, rather than try to squeeze more pixels into a small area, let’s just make the sensor bigger.” “If we want to double the megapixels, we'll just double the area of the sensor! That way pixel size stays constant!” Good thinking, mostly. The problem with this logic is that in order to avoid optical distortion, bigger sensors require bigger lenses and bigger camera bodies. This big-sensor solution you've just dreamed up already exists.  It’s called a digital SLR.  Here though, we’re talking about pocketable cameras, so there’s unfortunately a limit to how much you can increase sensor size, but you’ve got the right idea.
Enter the Canon S90
The Canon S90 attacks the too-small pixel problem from two directions. First, Canon bravely decided to actually drop megapixel count relative to competing products, choosing a relatively modest 10 megapixels for the S90. Second, Canon increased sensor size to 0.43 square cm versus the typical 0.28 sq cm it generally uses in a camera of this size. The result is a bigger sensor with fewer but larger pixels.  These two "improvements" togther give the S90 larger pixels than any compact digital camera currently on the market. In fact, Canon hasn’t put out a camera with comparably large pixels since 2006, when the produced the 6-megapixel SD700IS, which is a minor cult classic (for reasons not-unrelated to its generously-sized pixels). 
Most point-and-shoots do a solid job outdoors in bright light. This Canon does too – there’s none that's obviously better. The pictures are sharp and punchy, as you’d expect. But bigger differences emerge indoors and, more generally, in less-well-lit situations.  Most compact cameras take frankly mediocre pictures when the scene is no longer well lit; grainy and washed images are par for the course. The S90 is different. As hoped, those large pixel sites make indoor pictures shockingly good. They’re not DSLR-good, mind you, but they’re like nothing you’ve seen out of of the compact you're shooting with now.
Design-wise, the S90 is encased in a brushed black aluminum with a bright high-resolution 3.0" display.  The overall look is somber and somewhat uninspired. Considering the high MSRP, one might have hoped for a product that looks more reflective of its price.  But construction quality feels a cut above other compacts, even Canon’s own, whatever its aesthetic qualities.
We applaud Canon for focusing on overall picture quality, not megapixels.  We’re comfortable pronouncing the S90 the best pocketable digtal camera on the market today.
In terms of image quality, there are no other alternatives at this "pocketable" size.  If you're willing to go larger, you should certainly consider the S90's big brother, the Canon G11, which is based on the same fine sensor.  The Olympus EP-1 (and upcoming EP-2), and the Panasonic GF1 are others to consider  -- they've also been designed by engineers that have experienced large-pixel "enlightenment."  As a group, these cameras mark a detente in the megapixel arms race.  Score one for the digital photography enthusiast crowd, but this is an advance from which everyone will benefit.