Image resolution is high, returning an excellent score of 2000LPH vertical and horizontal on our test chart. ISO performance is also excellent; if you're not pixel-peeping, shots up to ISO1600-2000 can look quite acceptable. At higher ISO levels, image softness and noise is more evident, but it's admirable how Canon has kept the noise to a fine grain, and how it's mostly luminance noise so colors aren't adversely affected. It wouldn't be a stretch to say that the S100 produces some of the lowest noise images to be found from a digital compact camera. Together with the punchy Canon colors, the S100 definitely takes great looking photographs.
If we do pixel-peep, we see noise reduction kick in quite early at ISO400, which already results in some detail loss at that stage. Even though eagle-eyed shooters will find a little softness from ISO400 onwards, a good balance between detail and noise can be found up to ISO1600, and that's an impressive feat for a digital compact when you're not looking at 100% view. If you want to retain more detail, you can set noise reduction to 'low' in the menu, or shoot RAW.
Here are some 100% crops of a real-world ISO test. Click to see the original full-resolution images.
Of more concern is the corner softness that some users online and ourselves have seen in our test shots. Generally speaking, the middle aperture values from f/4-6.3 seem to fare best, while images shot outside of these aperture values have softer details in the corners. But we want to emphasize that we mention this for the more discerning user, we believe most users won't notice the corner softness in real-world images. Instead, for an everyday user who just upgraded from a previous compact, chances are that they'll see above average images which look better than their previous camera.
Here are a few 100% zooms of the corners of our test scenes shot at f/2.0, f/4.0, f/6.3 and f/8.0, all shot at the widest focal length of 24mm and ISO200.
A wide aperture like the Canon S100's f/2.0 lets you do a couple of things. It lets you grab more light and thus shoot at faster shutter speeds in low light, compared to a smaller aperture which lets less light in. It also produces soft backgrounds, providing more emphasis to your subject. The S100's background blur - or bokeh - isn't as creamy as you'd get from a DSLR camera and its larger sensor. It won't blow you away, but it's a good option to have on a compact. At 24mm you get the widest setting of f/2.0, while at the furthest zoom of 120mm you get a slower f/5.9.
We want to mention the useful Handheld Nightscene mode, which takes multiple shots and combines them together, helping you get a sharp image shooting in the dark even without a tripod. It works very well, even when the lens is zoomed to maximum, which is when shaky hands are most likely to produce a blurry image. It's better for still subjects than for moving subjects though, as moving subjects will create trailing artifacts.