CCTV Design Lens Calculator

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Camera View area

 

A dimensional figure in shape of a near-pyramid* with vertex abutting the camera lens and bisector, coinciding with the main optical axis of the camera lens.

Any object within the view area will be displayed on the screen, if it is not shaded by other objects on the scene.

 

View area has the form of a regular pyramid only if lens distortion is negligible. The lens distortion complicates the form of the view area.

 

* View area of panoramic cameras occupies half of space.

 

View area projections

 

Projections to horizontal and vertical planes of a view area part, which is residing between the view area upper and lower bounds specified in parameters in the View area tab.

 

View area horizontal projection is calculated according to the rule:

 

A point on the horizontal projection is considered visible if a vertical segment, formed by this point in the range of heights from the view area lower bound height to the view area upper bound height, is visible wholly.

 
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Image sensor size and size of active area of the image sensor

 

The Image sensor size implies the size of the entire light sensitive area of the image sensor, which can form an image with the maximum number of pixels horizontally and vertically.

 

Active area of the image sensor implies an area of ​​image sensor on which in a given mode of the camera the image is formed. The sizes of the active area may be less than or equal to the image sensor size. Active area can differ in different modes of operation of the same camera.

 

Exactly the active area size and lens focal length determines the angles of view, and through them influences on the results of camera modeling. Accuracy of specifying the active area size greatly affects the accuracy of modeling the camera.

 

Aspect ratio of the active area of image sensor is identical with the aspect ratio of the output image of the camera, but can differ from the aspect ratio of the image sensor.

 

On the figure on the right you can see the image sensor size and the active area of the image sensor in case of the image sensor has aspect ratio of 4:3, but the output image from the camera has aspect ratio of 16:9.

 

See also: Specifying active area size of the image sensor

 

Field-of-View

 

 

A flat* figure limited by view area bounds and residing in a plane, perpendicular to the main optical axis of camera lens.

 

The field of view has rectangular form only if lens distortion is negligible. The lens distortion complicates the form of the field of view.

 

* Field of view of panoramic cameras is  hemisphere shaped and has a bound in the form of circle.

 

Field-of-view horizontal and vertical sizes in dependence of the distance from the camera and camera view angles are calculated on the Pixel density tab, in the column Field-of-view.

 

 

 

 

Pixel density (spatial resolution)

 

The number of pixels which cover one unit of linear size (meter, foot) of the field-of-view at a given distance from the camera.  It is measured in pixels / meter, or pixels / foot.

 

The actual detail of the object's image is limited not only by the pixel density, there are also other factors which are difficult to be taken into account: compression, lens resolution, contrast, noise, etc.

Thus the pixel density determines the maximum achievable details of an object on a digital image. The real image of the object may be less detailed.

 

 

Camera tilt angle

 

A calculated parameter and can not be edited. The camera tilt angle is an angle between the main optical axis of camera lens and a horizontal.

 

Though in most of the cases the camera tilt angle is not interesting to designer, CCTV Design Lens Calculator is displaying it for information.

 

Camera tilt in CCTV Design Lens Calculator is determined not by the tilt angle but by the following three parameters:

 

 

 

 

 

Standard camera position

 

The most widespread camera position, when the Height of installation is more than the View area upper bound height.

 

 

 

CCTV Design Lens Calculator can correctly calculate all possible camera positions not only the standard one. For example:

 

 

 

For details about other camera positions see: View area parameters