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How Motion Detection Cameras Work

8 points by abennett 17y ago

ilamont 17y ago
"However, CCD produces higher quality images. Thus, security cameras generally use CCD technology." Assuming this statement is true, then why is it often difficult to make out suspects in security camera footage shown on TV news reports? The classic example is a case involving a theft or other crime at a mall -- facial features are never clear. Banks, however, seem to always have good images available when robberies take place. Is it an issue of placement, older technologies, or something else?
- MattF 17y ago
  There are a few reasons. There are still a lot of systems that still record to tape, typically in your local minimart, garage, etc. Cameras in malls have a large field of view and cover a large area, so there are very few pixels on target. And as the article implies, lighting plays a big role - it changes a surprising amount even in indoor installations. This is a very tricky problem and there is a lot of work being done in this area. Surprisingly one of the biggest issues is getting customers to realize that there is a real benefit to upgrading their cameras.
- brk 17y ago
  This article is actually very poorly written. For starters, one of the best CCTV image sensors on the market is from a company called Pixim, and it is CMOS, not CCD. The vast majority of CCTV cameras sold today are D1 (VGA) resolution. They are also often covering fairly large fields of view, so you end up with a few dozen pixels on target of someones face, or a license plate. It's impossible (other than on TV) to extrapolate that into useful detail. The "motion detection" systems described in this article are also false-alarm generating garbage in most cases. You need a camera that can definitively recognize and detect people, plus have some ability to a behavior analysis (direction of travel, loitering,etc.). An example from an actual camera on my driveway (with the Pixim CMOS sensor): http://www.youtube.com/videoiq#p/u/6/FbAWYB24Qdw http://www.youtube.com/videoiq#p/u/6/FbAWYB24Qdw Track the person. Not the dogs, not the water, not the shadows.

8 points by abennett 17y ago

"However, CCD produces higher quality images. Thus, security cameras generally use CCD technology." Assuming this statement is true, then why is it often difficult to make out suspects in security camera footage shown on TV news reports? The classic example is a case involving a theft or other crime at a mall -- facial features are never clear. Banks, however, seem to always have good images available when robberies take place. Is it an issue of placement, older technologies, or something else?

MattF 17y ago
There are a few reasons. There are still a lot of systems that still record to tape, typically in your local minimart, garage, etc. Cameras in malls have a large field of view and cover a large area, so there are very few pixels on target. And as the article implies, lighting plays a big role - it changes a surprising amount even in indoor installations. This is a very tricky problem and there is a lot of work being done in this area. Surprisingly one of the biggest issues is getting customers to realize that there is a real benefit to upgrading their cameras.
brk 17y ago
This article is actually very poorly written. For starters, one of the best CCTV image sensors on the market is from a company called Pixim, and it is CMOS, not CCD. The vast majority of CCTV cameras sold today are D1 (VGA) resolution. They are also often covering fairly large fields of view, so you end up with a few dozen pixels on target of someones face, or a license plate. It's impossible (other than on TV) to extrapolate that into useful detail. The "motion detection" systems described in this article are also false-alarm generating garbage in most cases. You need a camera that can definitively recognize and detect people, plus have some ability to a behavior analysis (direction of travel, loitering,etc.). An example from an actual camera on my driveway (with the Pixim CMOS sensor): http://www.youtube.com/videoiq#p/u/6/FbAWYB24Qdw http://www.youtube.com/videoiq#p/u/6/FbAWYB24Qdw Track the person. Not the dogs, not the water, not the shadows.