4.4. High Pass
| 4. Filtri di miglioramento |

### 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.

#### 4.4.2. Activating the filter

You can find this filter through Filters → Enhance → High Pass….

#### 4.4.3. Options

Figura 17.31. «High Pass» filter options

Presets, Preview, Split view

  These options are common to GEGL-based filters. Please refer to Sezione 2, «Caratteristiche comuni».

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

Procedura 17.1. Sharpening

1. Open your image:

2. Duplicate layer:

   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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