### 4.4. High Pass

#### 4.4.1. Overview

In sound processing, a high-pass filter filters high frequencies above a threshold. In digital images, frequency refers to sudden changes in brightness or color in neighboring pixels. The High Pass filter filters high essential details, and larger scale gradients are removed. This result, combined with the original image and "Soft Light" or "Hard Light" merge mode, is used to sharpen images. It enhances fine details.

#### 4.4.2. Activating the Filter

This filter is found in the main menu under Filters → Enhance → High Pass….

#### 4.4.3. Options

Figure 17.41. “High Pass” filter options

Presets, “Input Type”, Clipping, Blending Options, Preview, Merge filter, Split view

  | Note
  These options are described in Section 2, “Common Features”.

Std. Dev.

  Increasing this Standard Deviation lowers the filter threshold and more image details are taken in account for treatment.

Contrast

  Increase/Decrease contrast of treated details.

#### 4.4.4. Using High Pass Filter

Procedure 17.1. Sharpening

1. Open your image:

2. Use the Duplicate layers:

   command to duplicate your image. This duplicate layer becomes the active layer.

3. Open High Pass filter.

4. Change mode to Soft light (try Hard light also).

5. Settings and on-canvas view

4.3. Deinterlace |  | 4.5. Noise Reduction

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