A Live-Preview Digital camera (LPD) is a camera that uses a conventionally generated digital image (live-preview) on an electronic screen as its principal means of framing and previewing before taking the photograph. With the exception of very few live-preview dSLRs, any digital camera that has live-preview falls into this category.Many modern LPDs have a movie mode, and a growing number of camcorders can take still photographs. However, even a low-end LPD can take far better still pictures than a mid-range video camera, and mid-range LPDs have much lower video quality than low-end Video cameras. In addition, some newer camcorders record video directly to flash memory and transfer over USB and FireWire. Among digital LPDs, most have a rear liquid crystal display for reviewing photographs. They are rated in megapixels; that is, the product of their maximum resolution dimensions in millions. The actual transfers to a host computer are commonly carried out using the USB mass storage device class (so that the camera appears as a drive) or using the Picture Transfer Protocol and its derivatives, in addition firewire is becoming more popular and supported among more digital cameras. All use either a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor or novel sensors based upon either of those two principles, i.e. chips comprised of a grid of phototransistors to sense the light intensities across the plane of focus of the camera lens. CMOS sensors are differentiated from CCDs proper in that it uses less power and a different kind of light sensing material, however the differences are highly technical and many manufacturers still consider the CMOS chip a charged coupled device. For our purposes, a chip sensor is a CCD.
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