FOV Lense Calculator

Distance to Object			ft
Lens Size
Focal Length			mm
Field of view (H x V):
ft x ft
Calculate

This handy FOV calculator will help you in determining which lens is right for your application. Simply enter the distance to the object, camera format Example: 1/4, or 1/3 , and focal length of the lens. Click "Calculate" to see the field of view you can expect with that lens. It also works in reverse. If you know the field of view you need, enter it in and the distance to the object along with camera format to find the focal length you will need to get the field of view desired.

Surveillance Camera Lens Chart
(approximate values)

Lens Size	Viewing Angle		Field of View (in feet)
Lens Size	Viewing Angle		5 feet away		10 feet away		15 feet away		25 feet away		50 feet away		100 feet away
(mm)	Width	Height	W	H	W	H	W	H	W	H	W	H	W	H
3.6	74	55	7.5	5.2	15.1	10.4	22.6	15.6	37.7	26.1	75.4	52.1	151	104
4.0	69	49	6.0	4.5	12	9.0	18	13.5	30	22.5	60	45	120	90
4.3	65	45	5.6	4.2	11.2	8.4	16.7	12.6	27.9	20.9	55.8	41.9	111	84
6.0	42	32	3.8	2.9	7.7	5.7	11.5	8.6	19.2	14.4	38.4	28.7	77	57
8.0	32	24	2.9	2.1	5.7	4.3	8.6	6.4	14.4	10.7	28.7	21.3	57	43
12.0	22	17	1.9	1.5	3.9	3.0	5.8	4.5	9.7	7.5	19.4	14.9	39	30
16.0	19	15	1.5	1.2	3.0	2.5	4.5	3.6	7.2	6.1	14.4	12.2	28	24

Here is something which is very important to remember and is a very easy way of thinking about the right Focal length lens. It is easer to understand this whole field of view thing if you think about it this way. A wide angle lens at 25' would have a Horizontal field of view of 33.3' a persons face is only about 8" wide, 8" of a 33.3 foot field of view is only about 2% of the pixels on that Horizontal line which means, in the area of the face you only have about 10 pixels . If a face were 8x8" that's 100 dots. This is about the limit for facial recognition.

So here is a short cut below. I have identified the major concerns of people and I have listed the widest horizontal (H) view which is acceptable given the typical resolution of these cameras.
(if you use a camera with a higher resolution then 270,000 pixels you will have better recognition performance.

People are usually concerned about four major objects they want to identify. I have broken them down here.
#1 Facial Recognition. = 25' Horizontal Field of View
#2 Body Recognition (the ability to Identify someone by how tall they are, if they are male or female, long or short hair and adult or child =25' to 45'
#3 Licenses Plate Recognition (the ability to actually read the license plate number) =10'
#4 Car Recognition (the ability to type or make of car) = 60'-75'

The function of the lens is to collect light reflected from the scene and focus it into an image onto the CCTV camera sensor. Most CCTV applications use a fixed-focal-length (FFL) lens, which, like your eye's lens, covers a constant angular field of view (FOV). S a Fix focal length lens always has the same magnification. A large variety of CCTV camera lenses are available with different focal lengths (FLs), which will provide different FOVs (magnification) . Wide-angle 3.6mm, medium-angle 6.0mm, or narrow-angle lenses 12.0mm produce different magnifications and FOVs.