Performance is the weakest aspect of the S90, and, overall, it's not that bad. It's just that if you're expecting the fast performance of a digital SLR, you'll be disappointed. From powered off to first shot is 1.8 seconds and it's the same from shot-to-shot when shooting in high-quality JPEG; shooting raw the time extends to 3.4 seconds. Continuous shooting and saving in JPEG is about 1 frame per second. The S90's shutter lag is likely to be the sticking point for some because it's really no better than an average point-and-shoot: 0.5 second to focus and capture in bright conditions. The good thing is that it's nearly the same in low-light conditions at 0.6 second.
The S90's photo quality is impressive for a compact camera. However, like most of Canon's PowerShot line, ISO 400 is about the limit before you start seeing softening of fine detail. On the other hand, its photos have minimal noise and its noise suppression isn't heavy to the point of destroying all detail until ISO 3,200. The S90 lives up to Canon's improved low-light performance claims. Its colors are also consistent through to ISO 1,600 so usable photos at small print sizes are possible.
The lens is sharp and consistent from edge to edge. There's a small amount of barrel distortion at the camera's widest 28mm-equivalent position. The zoom is short on this camera--3.8x--so there was no reason to expect to find any pincushion distortion and there wasn't any. What was visible was some chromatic aberration that was a below average amount in high-contrast situations where you expect to see it, but it's noticeable in prints of 8x10 inches or larger (especially if you're sensitive to seeing it). Its color quality was excellent for coming from the little compact. Also, exposure and white balance were also generally very good from the S90, though as typical from pocket cameras there was highlight clipping.
Canon markets the PowerShot S90 as "the perfect everyday camera for people who are serious about great photography." This is close to on point, though I would change it to perfect everyday compact camera. The lens, controls, and shooting options make it a fine choice for enthusiasts. The S90's photo quality is on par with the best PowerShots, too, which is to say generally excellent. However, the S90s performance makes it best suited for portraits, landscapes, and the like--but not for fast-moving subjects.
(Shorter bars indicate better performance)
|Time to first shot||Raw shot-to-shot time||Typical shot-to-shot time||Shutter lag (dim)||Shutter lag (typical)|
(Longer bars indicate better performance)
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