Tech] Help determining which lens on security camera
Got a fixed lens security camera used. they made two different lenses for it:
The 2042 mini-bullet was available with:
4mm - Horizontal field of view: 83°
6mm - Horizontal field of view: 55.4°
Nothing on camera or lens to indicate which lens it is....
Camera is installed already....
I am trying to determine which lens the camera has.... So I can determine what the next camera I purchase should have -- 4MM or 6MM?
Can someone help me with the math?
If I know the aspect ratio of the image I'm looking at: 16x9
And I can measure the WIDTH of the image I see on a 16x9 display in the yard in feet as:..... "X"
And I can measure the DISTANCE from Lens to what I measured (as X) in feet as:..... "Y"
And I know the lens is either 4MM (83 Degrees) or 6MM (55.4 Degrees)....
What would the mathematics be to determine which of the two lenses that I have based on the WIDTH I calculate???
Thanks...