Cna someone help calculate the viewing angle for this lens?

[olpeculiar]

I am looking at a digital surveillance camera with the following lens specifications:

Lens Type: CS mount, f=6.0 mm, F1.8, Fixed

Is this enough information to calculate the angular field of view for this camera? If so, what would the angular field of view be? I found one calculator online, but it gave me a diagonal angular field of 148°, which seems ridiculously wide for a surveillance camera. I mean, wide viewing angles are good, but the fisheye distortion would be so bad you wouldn't be able to make out anything.

Can anybody help with this? (Use small words, I don't know much about photography and lenses and such...) Thanks!

- OlPeculiar

[beowulff]

You need to know the sensor size.

[Jaglavak]

http://en.wikipedia.org/wiki/Field_of_view

The "FOV formula"

{o / d} = {i / f}

where:

* f is the film distance (from lens to film plane). When the lens is focussed to infinity, this distance is equal to the effective focal length of the lens. Treating f as equal to the focal length is adequate for most purposes.
[8 mm in your case]

* d is the object distance (or "working distance" from lens to object along the optical axis).
[You choose. Often given at 100 ft]
* o is the object dimension (or "field of view" perpendicular to and and bisected by the optical axis).
[This is the unknown variable in your case]
* i is the image dimension (or "field stop" perpendicular to and and bisected by the optical axis).
[How big is your sensor?]



[Field of view] = [Working distance] * [Sensor size] / [Focal length]

"So for example, a 35 film frame has i dimensions of 36 mm horizontal by 24 mm vertical and 43.3 mm diagonal. Thus, the horizontal field of view using an 50 mm lens would be d × i / f = d × 36 / 50 = d × 0.72. At a working distance of 10 metres, the horizontal field of view is therefore 7.2 metres; at a distance of 100 feet, the horizontal field of view is 72 feet, etc."