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MX Cameras

3-8 Vicon MX Hardware System Reference

resolution frequencies given in MX Camera Specifications on page D-2, the

sensor area is reduced due to vertical windowing, as described in Field of View

on page 3-4.

Aperture and Depth of Field

Another significant factor in choosing a lens type is the aperture (also

known as the f-stop value, f-number, and F#), which refers to the

speed with which the lens can pass light in a given time.

The aperture is the ratio of the focal length of the lens to the diameter

of the lens opening, which determines the amount of light that can

pass through the lens in a given time. Smaller f-stop values (e.g. f2,

f2.8) represent wider apertures that allow more light to pass through,

while larger f-stop values (e.g. f11, f16, f22) represent narrower

apertures that allow less light to pass through. Typically, faster lenses

have larger diameter optics that can pass more light.

Each f-stop value changes the lens opening from the next f-stop by

a factor of 2. For example, decreasing the aperture from f11 to f8

allows twice as much light to pass through. Increasing the aperture

from f11 to f16 allows half as much light to pass through.

The aperture and magnification affect the depth of field, that is, the

portion of the image that has sharp focus. Immediately surrounding

this area, there is a region in which the image remains in focus.

Outside of this area, moving towards or away from the lens, the focus

becomes progressively less sharp and the image appears out of focus.

Thus, as the aperture and focal length decrease, the depth of field

increases. Conversely, as the aperture and focal length increase, the

depth of field decreases.

Camera Lens Filters

In order to optimize the performance of the MX Cameras, each lens

is fitted with an optical filter to attenuate wavelengths of light other

than those emitted by the light emitting diodes (LEDs) in the MX

strobe unit and reflected back from the markers to the camera.

Shuttered MX Cameras are less susceptible to interference from

background light levels. These cameras are fitted as standard with

low-pass absorptive filters (allowing low-frequency light to pass)

appropriate for each of the Visible Red (VR), Near Infrared (NIR), and

Infrared (IR) strobe units available.

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