感光元件大小???

數碼相機的『 吋 』數，現在是指感光元件﹝ charge-coupled device (CCD) detector ﹞ 的類型，雖然某程度上可以作為大小比較指標，但不能準確反映元件的真實尺寸，所以現在通常用 『 TYPE 』表示，例如 type 1/1.7 吋 CCD，而少用『 SIZE 』的，減低混淆及誤導。這種命名方法乃參照傳統圓形的攝像管﹝ Vidicon tube ﹞，而 CCD 其實是方形的。

CCD Formats：
『 ‧‧‧common dimensions of CCDs result from their early competition with vidicon tube cameras‧‧‧Note that the "inch" designations do not correspond directly to any of the CCD dimensions, but represent the size of the rectangular area scanned in the corresponding round vidicon tube. A designated "1-inch" CCD has a diagonal of 16 millimeters and sensor dimensions of 9.6 x 12.8 millimeters, derived from the scanned area of a 1-inch vidicon tube with a 25.4-millimeter outside diameter and an input window approximately 18 millimeters in diameter.‧‧‧often used in reference to CCD "type" rather than size‧‧‧1/1.8-inch CCD that is intermediate in size between 1/2-inch and 2/3-inch devices‧‧‧』
http://www.microscopyu.com/articles/digitalimaging/ccdintro.html

http://www.dpreview.com/news/0210/02100402sensorsizes.asp

面積較大的 CCD 有利光學影像放大，對於影像品質，還是要同時考慮其有效像素的，因為相同『 吋 』數的CCD 有效像素可以相差數倍，CCD 的『 吋 』數只能由生產商提供，相信不會有消費者會把相機拆開量度，所以只要比較光學放大和有效像素即可。
『 ‧‧‧ The increased magnification can be beneficial in some applications‧‧‧For a given CCD size, the design choice regarding total number of pixels in the array, and consequently their dimensions, requires a compromise between spatial resolution and pixel charge capacity‧‧‧』
http://www.microscopyu.com/articles/digitalimaging/ccdintro.html

相關資料：
1/1.8 吋 CCD 解像度由 3.3 million 至 6.3 million Pixel count
http://www.dpreview.com/news/0312/03121702sharpsixmeg.asp

CCD：
http://en.wikipedia.org/wiki/Charge-coupled_device

CCD elements：
http://www.sony.net/Fun/SH/1-22/h5.html

CCD sensor sizes table：
http://www.dpreview.com/news/0210/02100402sensorsizes.asp

Vidicon tube：
http://members.chello.nl/~h.dijkstra19/page4.html

Getting the Right Digital Camera：
http://www.ftpplanet.com/digital_photo/getting_right_camera.htm

CCD or CMOS acts as films in digital camera, after it captures the images it will save to your memory card. 1/1.7吋 1/1.6吋 1/2.5吋, refer the the size of the 'film', the bigger the size the better it will capture the image. So a 1/1.7" CCD is bigger than a 1/2.5" CCD, hence better.