Multi-Aspect Sensor
Although the maximum output of the GH2’s sensor is 16.05 million pixels, the actual sensor has 18.31 million photosites. The reason for this is that the GH2’s sensor is actually slightly larger than a standard Four Thirds sensor.
The default aspect ratio of a Micro Four Thirds sensor is, of course, 4:3. Usually, any other aspect ratio a camera produces is merely a crop of this. For example, the maximum 4:3 image size of the GF2 is 4000×3000 pixels, and the 3:2 ratio is a crop of this, measuring 4000×2672 pixels. Note how the width is identical, but the height of the image has been cropped to produce the different aspect ratio.
However, the GH2’s larger sensor is able to produce a 4:3 image that measures 4608×3456 (15.9m) pixels, while 3:2 images are 4752×3168 (15m) pixels. Although the height of the image is different, the slightly larger sensor maximises use of the imaging circle so that 3:2 images are actually wider than the native 4:3 ratio.
The benefit of this is that images maintain a resolution that is still reasonably high. This can be seen by the difference in resolution when looking at 4:3 images and 16:9 images produced by the GH2 and GF2. There is roughly a two-million-pixel difference in the size of images when switching between 4:3 and 16:9 on the GH2. This means that 16:9 images have around 12.5% fewer pixels than the 4:3 images. However, the 16:9 images produced by the GF2 are more than three million pixels smaller than 4:3 ratio images. This is a 25% reduction in the number of pixels.
So, the multi-aspect sensor means that there is less reduction in image size when the aspect ratio is changed from the standard 4:3 ratio.
