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Canon PowerShot G15 Digital Camera Review$499.99
There are three high-ISO noise reduction options on the G15, but much to our chagrin, none of them is "off." By default, the camera is set to Standard NR, but there are also Low and High options available. With the default setting, noise levels start at 0.49% at ISO 80 and don't top 1% until ISO 1600. Even at ISO 3200, noise is kept to an impressive 1.69%, and the real-world results look just as good. In short, the G15's noise reduction algorithms are among the best we've seen in this class at maximizing detail while minimizing noise. Things do fall off substantially at ISO 6400 and the maximum setting of ISO 12800, however, where you'll notice the camera taking more time after each shot to complete its processing.
At these higher settings, the images aren't really usable for more than drastically downsampled web shots, but up to ISO 1600 you should be able to get perfectly usable shots for most purposes. Compared to the competition, this is a very solid result. Of the cameras in the comparison chart below, the G15 is one of only two that offer a full-resolution ISO 12800 option (the other being the Samsung EX2F), and it's no coincidence that those two have the lowest scores. They're suffering there for their extended sensitivity range, but at like-for-like ISO comparisons they perform at least as well as the Panasonic LX7 and Canon G12. More on how we test noise.
Uncommonly for a compact camera, the G15 offers 1/3-stop ISO settings throughout its entire range. Starting at ISO 80, it goes all the way up to 12800, with a total of 23 options. The Auto ISO mode lets you choose your max ISO range, but limits it to ISO 1600 at the high end (which is likely the sensor's native high-ISO limit, the others being simulated in software). You can also set the Auto ISO mode's rate of change, choosing between slow, standard, and fast. This option determines how aggressively the mode reacts to lighting changes.