We loved Canon's HG20, even if it does lack one or two features which the video enthusiast could require. But Canon also offers an even more jam-packed model in the shape of the HG21. We put a sample through its paces to see how it compared.
There are essentially two extra features which the HG21 has that the HG20 doesn't. The most obvious is the viewfinder. Whereas the HG20 relies entirely on its flip-out LCD, the HG21 has a 0.27in eyepiece as well with a 123,000 pixel resolution. You won't find yourself using this very often, but it can still be useful if sunlight is washing the LCD out. It also extends for more comfortable use, unlike the viewfinder on Panasonic's HDC-SD100 and HS100. On the other hand, the HG21's LCD is the Multiangle Vivid version found on the HF10 and HF11, but not the HG20. This is brighter with wider angles of vision than the standard screen, making it easier to see in most conditions anyway.
The other major difference is the size of the internal hard disk. Where the HG20 offers 60GB of storage, the HG21 doubles this to 120GB. So where the HG20 can record a little over five hours of footage at the top image quality, the HG21 has room for over ten. You will probably find you can shoot multiple holidays and family events before ever having to consider clearing footage off - although we would recommend backing up sooner than that, as you don't want to lose cherished shots along with a lost camcorder.
A final difference is that the HG21 is black where the HG20 is silver, which is Canon's usual way of distinguishing a higher-end model from its more lowly but very similar sibling. Despite the viewfinder and larger hard disk, the HG21 hasn't increased in size over the HG20, but its weight is up by 25g. You probably wouldn't be able to tell the difference.
Other than these upgrades, the HG21 has identical features to the HG20 and HF11. It's built around a sizeable 1/3.2in CMOS sensor with a gross 3.31-megapixels, 2.07 megapixels of which are used when shooting video and 2.76 megapixels for photography. So footage is captured at a native Full HD resolution of 1,920 x 1,080, with digital stills up to 2,048 x 1,536 (with a bit of interpolation and a 4:3 aspect). The optical zoom is the same 12x, and Canon's excellent Super Range Optical Image Stabilizer is incorporated.