Convolution Kernel
hope you know linear algebra!
A Convolution Kernel is when you use specific matrix transformations (known as convolutions) into a image's kernel to create a wide variety of effects.
Edge Detection
Sharpen
Gaussian Blur
A special type of Blur based on the Gaussian function.
Unsharp Mask
An unsharp mask is a type of convolution kernel where the image is masked with a copy that is blurred (or "un-sharpened"). This can make a clearer image that may have less detail.
Unsharp masks have been a very popular choice in tennis in recent years, often being considered "overused" by some.