Unsharp Mask is a sharpening technique that selectively enhances the edges of an image, while preserving the overall smoothness of the image. It is commonly used for portrait photography because it can help to define the subject's features and create a more visually appealing image.

The primary goal of sharpening in portrait photography is to enhance the edges and details of the subject, such as the eyes, lips, and hair. This helps to create a more visually appealing image and draw the viewer's attention to the subject.

The Unsharp Mask filter has three parameters: Amount, Radius, and Threshold. Contrast is not a parameter of the Unsharp Mask filter.

Increasing the Amount parameter of the Unsharp Mask filter increases the overall sharpness of the image by enhancing the edges and details more strongly.

Increasing the Radius parameter of the Unsharp Mask filter increases the size of the area that is sharpened, which can result in a more noticeable sharpening effect.

Increasing the Threshold parameter of the Unsharp Mask filter decreases the amount of detail that is sharpened, which can help to reduce noise and grain in the image.

The High Pass Filter sharpening technique is best suited for images with a lot of fine detail because it selectively enhances the high-frequency details in the image, while preserving the overall smoothness of the image.

The primary goal of using a High Pass Filter for sharpening is to enhance the edges and details of the subject, such as the eyes, lips, and hair. This helps to create a more visually appealing image and draw the viewer's attention to the subject.

The High Pass Filter has two parameters: Amount and Radius. Contrast is not a parameter of the High Pass Filter.

Increasing the Amount parameter of the High Pass Filter increases the overall sharpness of the image by enhancing the high-frequency details more strongly.

Increasing the Radius parameter of the High Pass Filter increases the size of the area that is sharpened, which can result in a more noticeable sharpening effect.

The Median Filter sharpening technique is best suited for images with a lot of noise or grain because it selectively reduces noise and grain while preserving the overall sharpness of the image.

The primary goal of using a Median Filter for sharpening is to reduce noise and grain in the image while preserving the overall sharpness of the image.

The Median Filter has two parameters: Amount and Radius. Contrast is not a parameter of the Median Filter.

Increasing the Amount parameter of the Median Filter increases the amount of noise and grain that is reduced, which can result in a smoother image.

Increasing the Radius parameter of the Median Filter increases the size of the area that is sharpened, which can result in a more noticeable sharpening effect.