Mirrorless Camera Sensor Sizes
Sensor size comparison
Mirrorless cameras are becoming increasingly popular as consumers look for something better than compacts or for a more portable replacement (or supplement) to a DSLR. At the moment, mirrorless is the fastest growing segment in the digital camera market.
Broadly defined as interchangeable-lens cameras with no mirror box or optical viewfinder, mirrorless cameras tend to combine the best parts of DSLRs, like interchangeable lenses, with the best parts of compacts, like small size. They are usually thought of as cameras with DSLR-like sensors, but that's not always the case. Sensors can range from compact size to APS-C and even full frame, although the majority of models come with either Four Thirds or APS-C sized sensors.
Olympus and Panasonic - the two companies that started the whole mirrorless business back in 2008 - use Four Thirds sensors (17.3 x 13 mm), Nikon uses 1" CX sensors (13.2 x 8.8 mm), and Sony, Samsung, Fujifilm, and Canon use APS-C sensors.
Here is a graphical comparison of different sensor sizes (included are all mirrorless cameras from 2008 to 11/2012):
Broadly defined as interchangeable-lens cameras with no mirror box or optical viewfinder, mirrorless cameras tend to combine the best parts of DSLRs, like interchangeable lenses, with the best parts of compacts, like small size. They are usually thought of as cameras with DSLR-like sensors, but that's not always the case. Sensors can range from compact size to APS-C and even full frame, although the majority of models come with either Four Thirds or APS-C sized sensors.
Olympus and Panasonic - the two companies that started the whole mirrorless business back in 2008 - use Four Thirds sensors (17.3 x 13 mm), Nikon uses 1" CX sensors (13.2 x 8.8 mm), and Sony, Samsung, Fujifilm, and Canon use APS-C sensors.
Here is a graphical comparison of different sensor sizes (included are all mirrorless cameras from 2008 to 11/2012):

Side by side comparisons
For a more in-depth examination of sensor differences (pixel pitch, pixel density, etc.), take a look at a few side-by-side comparisons of popular mirrorless cameras: