Good specs for facial recognition?

[mensb 0]

Hi, these be good specs for facial recognition (day or night)?

 

1/3-inch digital color CCD cylinder camera. 540 TVL, 12VDC, NTSC

 

Lens Type: Internal 4mm - 9mm Varifocal

External Adjustment: Yes

Sensor Type: 1/3-inch Sony Super HAD™ CCD

Effective Pixels: 768 (H) x 494 (V)

Scanning System: 2:1 Interlace

Horizontal Resolution: Color: 540 TV Line

Iris Control: Auto

CCD Shutter Speed: 1/60 - 1/10,000 second

Auto Iris: DC

Minimum Illumination: 0 lux:LED On, 1.0 (F/1.2):LED off

S/N Ratio: >48dB

Automatic Gain Control: Auto

Electronic Shutter Control: Auto

White Balance Mode: Auto

White Balance Range: 3200 ~ 10000 ºK

Sync Type: Internal

Signal Processing: Digital Signal Processing (DSP)

IR Range: 30M 35º

[NotoriousBRK 0]

Your camera (any camera) has a fixed number of pixels.

 

If you spread those pixels over a very wide area, then each pixel is taking a large amount of square-footage area and storing it as a single averaged pixel/color.

 

If you spread those pixels over a very small area,then each pixel is storing a smaller amount of area, which yields better detail.

 

This is usually discussed as "pixels per foot", or how many pixels are spread over 1 foot of real-world area.

 

To get good object detail (faces, license plates, etc.), you usually want at least 70 pixels per foot, and more like 80-100. You also need good light at night. This usually means a real light source (floodlight or real IR illuminator), not 12 cheap LEDs sprinkled around the lens.

 

The pixels per foot math is easiest to do on the horizontal axis. The camera you quoted has 768 pixels on the horizontal axis. We want to have at least 80 pixels per horizontal foot.

 

So: 768 / 80 = 9.6

 

As long as you keep the shot less than 10 feet wide, you'll be getting very good detail. As you go wider than 10 feet, object detail will start to fall off. More than 20 feet wide and it will be very noticeable.

 

You can then use a standard lens calculator to tell you that at 4mm the shot becomes 10ft wide 10 feet from the camera. At 9mm it becomes 10feet wide about 22feet from the camera.

 

So, keep the camera within 20 feet of where you want to detect faces and you should be able to zoom it in enough to get good detail.