Guide to Identifying or Recognizing a Face: Resolution, Focal length, and Megapixels
If you have ever said "I need to ID a face at ___ distance, what camera should I buy?" then this guide is for you.
This guide covers a person in full daylight who is looking towards the camera and is organized by resolution and lens focal length (more commonly called "zoom"). As you zoom in, your field of view narrows.
Identify vs Recognize vs. Detect
These three terms, although sounding similar, are actually different. Let's define them before proceeding.
Detection is the most basic of the three terms and refers to being able to detect that a human face is in the picture. Industry standards state that you can tell a face is a face if it is at least 4 px in size.
In the picture to the left, you can detect that a person is in the frame, but you cannot recognize or identify who they are.
Recognizing a face refers to being able to say "I have seen that person before," even if you don't know or can't place who it is. Industry standards state that you can recognize the face of someone you have seen if it is at least 20 px in size.
In the second picture to the left, you can recognize the person in the frame (You might say "I know I have seen him before, but I don't know where" or "That's the guy from the SCW website!"), but without having the other photos on this site as a reference, you couldn't really do anything. As long as you can recognize someone in a picture or video while they are committing a crime, you can press charges, but you will need to have identified them previously.
Identification is the most involved term and refers to being able to make out identifiable marks with enough certainty to make a claim. Industry standards state that you can identify a face if it is at least 40 px in favorable conditions and 80px in challenging ones (twilight, a rainy day, the person not looking at the camera, etc).
In the third picture to the left, you can identify this face and a police sketch artist should be able to draw it.
Distance for Recognition, Quick Nav
From 10 Feet Away
1080P at 2.8mm
110 degrees view
2.8mm lens setting
Most cost effective-camera: Deputy 2.0
From 20 Feet Away
From 50 Feet Away
From 75 Feet Away
4MP at 4mm
81 degrees view
4mm lens setting
Most cost appropriate camera: Warrior 4.0
From 100 Feet Away
From 125 Feet Away
From 150 Feet Away
From 175 Feet Away
4K at 12mm
35 degrees view
12mm lens setting
Most cost effective-cameras: Judge 8.0 4K or Gladiator 8.0 4K
From 200 Feet Away
From 400 Feet Away
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