On Sun, 9 Nov 2003, Robert Gonzalez wrote: > John Francis wrote: > > Ah, but we *do* know for a FACT that the sensor is being cleared. The > > sensor is used to provide live preview on the LCD display, and needs to > > be cleared before being used to capture the real image. > > Interesting. I know that it must clear the sensor array, that is a > given, otherwise the sensor sites, which are tiny capacitors, would > saturate. And this probably takes place (I'm speculating) for every > frame it puts out while providing a live image. I'm wondering whether > it needs to do a separate, special clear before it captures the image, > and if so why? And if so, how long? Any ideas? My suspicion is that > the frame rate to the LCD live display sets the mininum clear time and > that there is no "special" clear, only a longer or shorter, post-clear, > capture, which reflects the "shutter speed" of the image.
When the cameras are showing the live display they are running in a lower resolution "movie" mode. They also don't clear the sites as well, on most cameras you can see this as blooming or smearing if the camera is aimed at a bright light in an otherwise dim room. It is at least true on the CCDs in the Sony DSC-F717 (also used in most other 5mp "prosumer" cameras) and the Sony DSC-S75 (used in the Canon G1 and many other 3mp "prosumer" cameras from that era). When it is time to take a real picture the CCD is switched into a full resolution still mode and all of the sensors are cleared. This is also the only time that the shutter on the camera is closed. I cited documentation on this a few weeks ago if you want to browse the archives. I don't have time to find it again right now though. alex
