Four Thirds System sensor at 26% of full frame, APS-H sensors (used, for example, in the Canon EOS-1D Mark III) at around 61% of full frame, and the original Foveon X3 sensor at 33% of full frame (although Foveon sensors since 2013 have been APS-C sized). Leica offers an "S-System" DSLR with a 30×45 mm array containing 37 million pixels. This sensor is 56% larger than a full-frame sensor. The resolution of DSLR sensors is typically measured in megapixels. More expensive cameras and cameras with larger sensors tend to have higher megapixel ratings. A larger megapixel rating does not mean higher quality. Low light sensitivity is a good example of this. When comparing two sensors of the same size, for example, two APS-C sensors one 12.1 MP and one 18 MP, the one with the lower megapixel rating will usually perform better in low light. This is because the size of the individual pixels is larger, and more light is landing on each pixel, compared with the sensor with more megapixels. This is not always the case, because newer cameras that have higher megapixels also have better noise reduction software, and higher ISO settings to make up for the loss of light per pixel due to higher pixel density. Depth-of-field control The lenses typically used on DSLRs have a wider range of apertures available to them, ranging from as large as 0.9 to about 32. Lenses for smaller sensor cameras rarely have true available aperture sizes much larger than 2.8 or much smaller than 5.6. To help extend the exposure range, some smaller sensor cameras will also incorporate an ND filter pack into the aperture mechanism. The apertures that smaller sensor cameras have available give much more depth of field than equivalent angles of view on a DSLR. For example, a 6 mm lens on a 2/3″ sensor digicam has a field of view similar to a 24 mm lens on a 35 mm camera. At an aperture of 2.8, the smaller sensor camera (assuming a crop factor of 4) has a similar depth of field to that 35 mm camera set to 11. Wider angle of view The angle of view of a lens depends upon its focal length and the camera's image sensor size; a sensor smaller than 35 mm film format (36×24 mm frame) gives a narrower angle of view for a lens of a given focal