Canon PowerShot G15 review
The most important change made to the PowerShot G15 is the inclusion of a 12.1-million-pixel CMOS sensor, although it measures 1/1.7in (around 7.6x5.70mm), which is the same as that on the preceding PowerShot G12. In addition to the extra 2 million pixels of resolution compared to the G12, the sensor has also shifted from CCD to CMOS technology in the G15. This switch to CMOS should help reduce power consumption and provide the quicker processing speeds required for faster frame rates and HD video. This is because some of the basic processing required for these tasks is done within the CMOS sensor architecture, whereas on a CCD sensor it is carried out by the camera's processing system.
Handling the camera's data is Canon's Digic 5 processing system. This isn't the first time we have seen a Canon PowerShot model with this combination of sensor and processor, as it was also used in the PowerShot S100 (see AP 3 December 2011). In fact, the G series is the last PowerShot line to receive the new 12.1-million-pixel sensor; both the S compacts and SX bridge cameras now have second-generation cameras that use this very combination.
The sensor is also one of Canon's HS units, which are backlit, meaning that much of the circuitry lies at the back of the sensor, allowing more of the sensor's surface to receive light. This is designed
to ensure that more light photons reach the photodiodes, which should result in reduced levels of noise and increased dynamic range due to more detail appearing in shadow areas. All this, in
turn, means the sensitivity range of the sensor is increased from ISO 80-3200 in the G12 to ISO 80-12,800 in the G15. Of course, this isn't all down to the new CMOS sensor - improvements in
noise reduction algorithms also have a part to play.
Optically, there have also been changes. The focal length of the G15's built-in zoom lens is still the same 6.1-30.5mm (28-140mm full-frame equivalent) range as its predecessor, but the maximum aperture has increased from f/2.8-4.5 to f/1.8-2.8. The number of elements remains the same as in the previous lens, with 11 elements in nine groups, but it now contains one single-sided aspherical lens, one ultra-low dispersion lens and two double-sided aspherical lenses.
The larger aperture should help low-light performance and allow for a faster shutter speed when using the maximum zoom, as well as creating a slightly shallower depth of field for portraits or close-up work. As before, the lens is optically stabilised, with Canon claiming a 4EV reduction in usable shutter speed.
Helping to make sure that your images are perfectly straight, there is also a new dual axis level that displays both side-to-side, and front-to-back tilt - so no more excuses for wonky horizons.
There are a number of other changes, including significant improvements to video capture, a fixed screen, faster AF and a redesigned body, but more on these later.