Pixels per foot.

[freqflyer]

I'm trying to determine how high of a resolution camera I need. I've been reading about sizing cameras by pixels per foot of the image being recorded.

I have read that 40 pixels per foot is sufficient for facial recognition. However, I have also read that 50 is required.

What do you guys suggest?

 

[nayr]

I suggest 100ppf minimum if you want any chance in hell at night.. 50 could get you by in the day, but bah.. I am @ 180-220ppf to get nice clean plate reads at night.

http://ipvm.com/calculator

 

[freqflyer]

How are you able to read a plate at night? I thought the reflective coating on the plate messed up the image.

 

[Kawboy12R]

You can read a plate visually under good lighting conditions below 40 ppf. Same thing with people you know. A good ID on a perp you don't know that you can't place on the scene? You really want 100ppf or better with good lighting and no blur.

 

[nayr]

I can only see plates at night with that camera, at 1/500 shutter speed its no longer an issue..

 

[freqflyer]

Please elaborate. With what camera? and what's no longer an issue. Is that with ir lighting on the camera or just what is coming from the car?

 

[nayr]

for this the camera dont matter, you have to change the exposure settings.. yeah thats with IR lighting @ ~170ft.

faster shutter = less light gets to sensor, the plates are being over-exposed.. so you decrease the amount of incoming light, everything goes black but bright light sources.. and man do they gotta be bright.

to read plates at night you have to simply increase shutter speed until plates come into readable form.. while sacrificing the ability to see pretty much anything else.

on my ptz's I have a controllable aperture, and I can close it to get plates readable without messing with shutter speeds.. but only parked, at the slow shutter speed they blur like hell in motion.