# Cna someone help calculate the viewing angle for this lens?

**URL:** <https://boards.straightdope.com/t/cna-someone-help-calculate-the-viewing-angle-for-this-lens/486159>\
**Category:** In My Humble Opinion\
**Created:** [February 16, 2009, 8:37pm UTC](https://boards.straightdope.com/t/cna-someone-help-calculate-the-viewing-angle-for-this-lens/486159 "2009-02-16T20:37:20Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![olpeculiar](https://avatars.discourse-cdn.com/v4/letter/o/34f0e0/32.png) [@olpeculiar](https://boards.straightdope.com/u/olpeculiar)\
**Post date:** [February 16, 2009, 8:37pm UTC](https://boards.straightdope.com/t/cna-someone-help-calculate-the-viewing-angle-for-this-lens/486159/1 "2009-02-16T20:37:20Z")

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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

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**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [February 16, 2009, 11:23pm UTC](https://boards.straightdope.com/t/cna-someone-help-calculate-the-viewing-angle-for-this-lens/486159/2 "2009-02-16T23:23:55Z")

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You need to know the sensor size.

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**Author:** ![Jaglavak](https://avatars.discourse-cdn.com/v4/letter/j/85f322/32.png) [@Jaglavak](https://boards.straightdope.com/u/Jaglavak)\
**Post date:** [February 17, 2009, 8:20am UTC](https://boards.straightdope.com/t/cna-someone-help-calculate-the-viewing-angle-for-this-lens/486159/3 "2009-02-17T08:20:38Z")

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> **[Field of view](https://en.wikipedia.org/wiki/Field_of_view)**
>
> The field of view (FOV) is the angular extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to electromagnetic radiation. It is further relevant in photography.
> In the context of human and primate vision, the term "field of view" is typically only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles or virtual reality goggles. N...

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.”