The PowerShot S90 is Canon's attempt at making a "serious" compact camera in shirt-pocket format. It's black, relatively expensive, not much bigger than a deck of cards, and it's really good at what it's made for, while being completely unsuited to doing what it's not made for. I like that in a camera, other than the expensive bit anyway.
FeaturesThe S90 packs a lot of features in its small body, and most of these are genuinely useful -- geared toward making the camera usable in a wide range of conditions, and giving the photographer lots of meaningful control over what it does. It has a bright (f/2.0 at the wide end) lens with a "human-scale" zoom range of 28 to 105 mm equivalent, it has all of the standard exposure modes, it is fully RAW capable, it has a largish sensor with a lowish (10M) pixel count, and it comes with pretty effective optical in-lens image stabilization. The LCD is large, bright, and pretty sharp, too.
It does standard-def video. I'm not much into video. We don't even have a high-def TV (although my computer monitor would certainly qualify). I only shoot short clips as "moving snapshots" in situations where I'd otherwise (and also) shoot regular still snapshots, and all I do with them is look at them occasionally and post them on Flickr where they're compressed beyond all recognition, which means I'd probably be happy with a cell phone camera for that purpose. Therefore, all I can say about that is that it gets the job done for me -- the few Christmas clips I took in pretty crappy light turned out quite nice, crisp, non-artifacty, without a whole lot of noise, except that the camera adjusts exposure in steps rather than smoothly, which made the picture brighten and darken a bit jumpily.
HandlingOne of the S90's selling points is that it puts as much photographic control behind physical buttons and dials as is possible in such a small package, and it makes the package customizable. The most innovative usability feature is the click-stopped ring around the lens. Its function can be changed with a button on the top of the camera, and it shifts to various purposes depending on the shooting mode. Together with the rotating thumb dial, the four-way rocker switch, and the programmable [S] button, this gives full control over any of the exposure parameters (shutter speed, aperture, exposure value, ISO) plus focus (manual, auto on half-press, auto with AF lock) in any of the shooting modes.
The way the controls reconfigure them in the different shooting modes is initially confusing, but once I got the feel for the logic with which this happens, it started to feel quite natural. I especially like the fact that the C(ustom) mode lets me preset both the focal length and focus to "street mode" -- i.e., medium-wide, wide-open, focus set to manual and more or less hyperfocal.
Three Way Traffic, Tokoinranta, Helsinki, 2009
The only real problem I have with the handling is that the rear dial isn't click-stopped. That means that it turns pretty much by itself, which means that I have to always check that I haven't accidentally nudged whatever it controls (usually exposure compensation) where it doesn't belong. A relatively minor problem, but a puzzling one as it's pretty damn obvious and would have been very easy to avoid -- and Canon has click-stopped rear wheels on their SLR's, and has had for decades.
Of course, a camera this small doesn't handle as well as a bigger one -- it's easy to put a finger on top or in front of the (surprisingly powerful) pop-up flash, it's not always easy to hit the right buttons especially with gloves on, the wrist strap will float in front of the lens if I'm not watching out, and so on -- but none of these things have obvious fixes that would not involve making the camera significantly bigger, which would sort of defeat the purpose of the design in the first place. I'm generally pretty fussy about ergonomics, but you have to make allowances for size.
Overall, I'd give the camera an A- for handling and accessibility of the shooting controls, when taking into consideration its size. In absolute terms, it'd be about a B- or C+: better than, say, the Sony DSC-V3, but of course nowhere near as good as any dSLR I've used -- or the Minolta Dimage 7i that I owned and loved for a while. That ugly, plasticky little monster is, in my opinion, still the best-handling non-dSLR digital camera that I've used.
PerformanceThe S90 is a solid performer, with no truly outstanding features but no huge flaws either. Metering is reliable and unsurprising, auto white-balance gets the job done well enough most of the time, auto-focus is precise and about average speed for a small compact like this. What's more, it's possible to assig AF lock to the [S] button, which makes pre-focusing a breeze, though, making focus speed not a concern for most situations. Shutter lag when pre-focused, either by half-pressing or with the [S] button, is virtually nonexistent making for very precise timing -- at least as good as with the film Leica CL I'd love to shoot if I could just put up with the bother of dealing with film.
Shot-to-shot time is sufficient for my relatively deliberate shooting style, although someone who likes to grab a series of shots in a situation might feel differently. I haven't felt like I'm waiting for the camera in any situation, except when using the flash in cold temperatures -- it takes a few seconds to charge up. For comparison, the Sigma DP1 feels really, really sluggish; its slow shot to shot time is really my biggest single beef with it.
Battery life is one area where the S90 is noticeably worse than its predecessor in my bag (the Fuji F100FD). Where the Fuji would keep shooting for what felt like forever, the S90 will start warning about low battery after a couple of hundred frames. I hate shepherding chargers, and I really wish that camera manufacturers would do what phone manufacturers just agreed to do, and settle on a single, standardized charger. USB, for example.
Image qualityFirst, let's get something out of the way: this is not an SLR. It's a shirt-pocket sized small-sensor camera with a tiny standard zoom. In other words, if you're expecting it to deliver the same quality as, say, an EOS-5D with a nice prime like the 35/2.0, then you'll be disappointed. Nor does it come close to the maximum attainable image quality of the DP1 with its almost arrogantly sharp 28/4.0 equivalent lens.
However, for what it is -- a small-sensor, zoom-lens ultracompact --, the picture quality is pretty amazing, really. I'd say that it puts up a pretty good fight with an entry-level digital SLR using its kit lens, candela for candela... assuming you shoot RAW.
Sensor qualityI've left ISO on AUTO, which works well for me. The camera will bump up the ISO once the shutter speed drops to about half the 35-mm-equivalent focal length. It goes cheerfully up to ISO320 or thereabouts, and then drags it up from that more reluctantly up to ISO1600. From where I'm at, that strikes a pretty good balance between noise and blur for hand-held shooting.
When shooting RAW and tweaking the sharpening and noise reduction parameters in conversion, the camera produces a perfectly usable ISO1600 -- I'd say it's roughly comparable to ISO3200 pushed to ISO6400 on my EOS 5D, except without the pattern noise that sometimes starts to emerge. ISO800 looks more or less like straight ISO3200 on the 5D, and ISO400 is perhaps a bit better than ISO1600 on it. In other words, it's about a stop to two stops behind the 5D sensor, which has a roughly similar pixel count but is about eight times bigger.
Helsinki Venice, Hakaniemi, Helsinki, 2009
When sharpening and luminance NR both turned off, and chroma noise reduction turned up about halfway, the high-ISO photos come up looking grainy and slightly soft, but rather pleasant -- not unlike ISO400 color neg or slide, actually, and a great deal better than high-speed color film.
At lower sensitivities -- ISO80 to about ISO200 -- the S90 is remarkably clean, about comparable to ISO400 on the EOS 5D.
Trucks in the Mist, Hakaniemi, Helsinki, 2009
I haven't even attempted to measure the dynamic range of the sensor, but it seems decent enough -- I have to watch the highlights a bit more than on an SLR, but that's only to be expected for a small sensor. The Fuji F100FD with its high-DR, high-ISO modes is better in this respect, but then you can do the same thing by underexposing and pushing the RAW file a stop or even two (assuming you're metering at ISO400 or less).
Earth to Sea, Töölönlahti, Helsinki, 2009
That's pretty damn amazing for a small sensor, in my opinion. It's certainly the first small sensor I've come across that trounces the one on the Fuji F30, ISO for ISO: in practice, it's about a stop ahead for ISO400 and above. When converted with a gentle touch, the pictures come out looking very dSLR-like, with the fine detail, few artifacts, and subtle gradations I'm used to seeing from them. I have come across no sensor-related artifacts such as banding or other pattern noise when not pushing the sensor beyond the ISO80-1600 range it's built to handle.
As an aside, Canon's DPP does a pretty good job of the conversions and is, in its current incarnation, quite pleasant to use. However, Adobe Lightroom 3.0 Beta produces better pixel-level quality. In particular, DPP occasionally produces odd moiré-like "patterns of smear" in areas with high-frequency detail such as gravel, fabric, or vegetation; Lightroom renders them beautifully. None of this is visible in 20 x 30 cm prints, though; I imagine you'd have to print at least A3 size for it to show up even under close examination.
Lens qualityThe lens on the S90 is about as good as an entry-level or mid-range dSLR standard zoom. It's not bitingly sharp and is a hair lacking in contrast, and it gets a bit soft toward the corners wide-open at the wide end, but then it's not really bad at any focal length or aperture either. Center sharpness is pretty good and very consistent all through the range. It has a bit of lateral chromatic aberration, and some purple fringing towards the corners; the former can be very effectively addressed in post-processing, and the latter is about what you'd expect in a standard zoom.
The lens has a quite a bit of barrel distortion at the wide end. However, the camera's JPEG engine, and Canon DPP, will automatically correct this if you let it. Adobe Lightroom 3.0 beta won't (although I understand that the final version will).
One area where the lens does rather well is flare resistance. The occasional flare spot does show through in extreme conditions, but they're relatively dim, relatively rare occurrences, and the camera does not show veiling flare -- washed-out shadows in contrasty conditions -- very easily.
Sunlight through Plexiglas, Tokoinranta, 2009
The interesting thing is that the lens is bright: at f/2.0, that's a stop more than most other compact digital cameras and nearly two stops more than a typical standard zoom (say, the optically comparable Canon 28-105/3.5-4.5 USM I have in my bag somewhere). That goes a long way to making up for the sensitivity advantage large dSLR sensors have -- at the wide end, anyway.
What's it good for?The PowerShot S90 is just about the best take-anywhere camera currently on the market. Compact size is of paramount importance in this mission, and while there are cameras out there that are smaller, none of them offer easily accessible full photographic control or anywhere near the kind of low-light capability the S90 has. It has a few correctable usability niggles (in particular, the spinny rear dial), but in my opinion no truly glaring flaws; its control scheme is unusual enough to require a bit of practice to learn to use and appreciate. It's not a camera for complete photography novices, though, although it does work perfectly competently in auto-modes as well; the number of buttons and dials and the number of functions they control will seem confusing to start with.
With reasonable camera technique and gentle RAW conversion, the S90 will get the picture in the box just about as well as a dSLR with a kit zoom, even if it can't match the image quality of a larger-sensor camera with a truly exceptional lens, such as the Sigma DP's or the micro-4/3 cameras from Olympus or Panasonic paired with their fantastic pancake primes. This is a camera for photographing human-scale subjects at human distances, not stuff like wildlife or sports, and it excels in that mission. The combination of a bright lens with a sensor that holds up well at high sensitivities, and Canon's tried-and-true image stabilization, means that taking indoor situationals without a flash is no problem at all. With the greater depth of field afforded by the small sensor, I'd go as far to say that it works better for this mission than my EOS-5D with a bright lens -- it's harder than you might think to get focus on the nose with an f/2.0 or brighter lens.
Tower, Christmas, 2009
The Canon S90 takes the single, big advantage of a small sensor -- compact size -- and squeezes the maximum of photographic capability out of it, particularly tailored for low-light human-scale shooting. Significantly pushing its limitations would inevitably impose a bigger body. This is what the S90's bigger sibling, the PowerShot G11, does. It is significantly more capable in many ways, but at that size and price, why not go the extra mile and go with an EP-1, EP-2, or GF-1, or perhaps one of the Sigmas if you don't mind doing the work needed to get it to produce the magical quality of which it's capable?
I still think that my ultimate take-anywhere camera would be something like the Sigma DP2 done right, with truly responsive performance, a good LCD, and consistent image quality that you don't need to jump through hoops every time to get. This doesn't appear to be on the cards right now, at any price; even the Leica X1 is significantly limited in many of the same ways as the Sigma DP's. The S90 comes closer to that ideal than any digital camera I've yet used, and I have a feeling that it'll be a quite a while before something even closer to it comes along.
Red Yarn Package, Kaisaniemi, Helsinki, 2009