Resolution for face recognition?

[claustro 0]

I am totally noob in this field , and I am trying to make a very basic surveillance system in my house.

I already wrote here http://www.cctvforum.com/viewtopic.php?f=19&t=30492 something about it, but I would like to ask:

what resolution is needed for face recognition in the 3-4 meters range? ( 13 feet away)

 

 

Thank you

Andrea

[Soundy 1]

Axis has a good article on pixels required for recognition and identification: http://www.axis.com/edu/identification/resolution.htm

 

In short, they say a face should be 17 pixels wide for recognition or 40 pixels for identification.

 

Based on this calculator: http://cctvlenscalculator.com/: 4CIF/D1 resolution, 1/4" sensor, 4mm lens, camera mounted 3m high at 4m distance, faces will be about 20 pixels wide. To get to 40 pixels (identification), you'd need to go to an 8mm lens.

[claustro 0]

Thank you very much for you answer .. very exaustive

.

[ssmith10pn 0]

FBI recommends 90 Pixels per foot density.

[buellwinkle 0]

Actually the Axis course I took said the head should be 40 pixels tall to recognize a known person, 80 for others but consider this, there are shadows, odd lighting, cameras have sharpening and noise reduction artifacts that dimish effective resolution. Then add noise at night and focus may not always be where you want it for the subject so 80 pixels tall is a bare minimum.

[thewireguys 3]

This is a good reference but keep in mind this is under idea lighting conditions

 

 

[ak357 0]

Actually the Axis course I took said the head should be 40 pixels tall to recognize a known person, 80 for others but consider this, there are shadows, odd lighting, cameras have sharpening and noise reduction artifacts that dimish effective resolution. Then add noise at night and focus may not always be where you want it for the subject so 80 pixels tall is a bare minimum.

 

Tall ?

[akelley 0]

This is a good reference but keep in mind this is under idea lighting conditions

 

Being from Jersey I take offense at the Jersey plates. Are you implying that there are more criminals in Jersey that need surveillance? And that guy could easily be mistaken for my cousin "Vinny", if you know what I mean.

 

[buellwinkle 0]

Yes, tall pixels, don't like using short pixels

 

It's easy to take a nice posed photo with perfect lighting but that's a lousy example. Take a real world shot from a surveillence camera and use that to make your comparisons. I have video clips from Jersey in my latest review on my blog, place where quality surveillance is well appreciated.

[torrance 0]

I shoot for 80, that is a pretty good picture. It depends what you are trying to do, if it's the neighbor's kid 40 may be adequate...Best is to get two cams one wide, the other on a spot where people always walk through (door etc).