Only features with keypoint.hessian larger than that are extracted.
good default value is ~300-500 (can depend on the average local contrast and sharpness of the image).
user can further filter out some features based on their hessian values and other characteristics
Namespace: Emgu.CV.Features2DAssembly: Emgu.CV (in Emgu.CV.dll) Version: 2.2.1.1150 (2.2.1.1150)