# Filter Objects by Size

Media Server can reduce the number of false positive results, by checking whether the size of an object, in pixels, corresponds to the real-world size of such an object at the relevant distance from the camera.

To configure this, set the configuration parameter `MaxPerspectiveError` in your object class recognition or vehicle model recognition task. This specifies the maximum percentage difference, between the size of a recognized object and its expected size. For example, to ignore objects that are more than 100% smaller, or more than 100% larger, than the known dimensions for their object class:

    [ObjectClassRecognition]
    Type=ObjectClassRecognition
    Recognizer=MyRoadUsersRecognizer

    // Perspective features
    FieldOfView=75
    WorldDimensionsMetadata=dimensions(m)
    MaxPerspectiveError=100

Micro Focus recommends that you allow a relatively large margin of error. Rectangular bounding boxes rarely fit perfectly around real-world objects, and the dimensions that you set are the average dimensions for all of the objects in a class. Even a relatively large `MaxPerspectiveError`, such as 100%, is likely to eliminate false positives that would not be excluded without taking perspective into account.

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