Using the Digital Camera Noise Removal Filter

The tiny, non-uniform speckles that can sometimes appear in digital photos are referred to as "noise." These unwanted image artifacts usually derive from inevitable sources such as JPEG file compression, or even as a result of electronic fluctuations inside a digital camera. A good example would be a photo of a clear blue sky. Zooming in may reveal tiny specks of color that you know are not present in the sky. You can use this filter to identify and remove noise while preserving detail smaller than the noise itself.

In addition to scanning and identifying three potential noise regions (in the highlight, midtone, and shadow regions of the image), the Digital Camera Noise Removal filter lets you target additional image areas for noise removal. This filter works on the entire image, or on a selection.

Camera Presets and Standard Presets

This filter gives you the option of creating a Camera preset. When a Camera preset option is checked, the Presets drop-list will only display these special types of presets. When you load a camera preset, the image is not sampled at all, but instead the camera preset settings are applied. You can still create additional sampling regions, however. Using a camera preset is recommended when your camera produces consistent noise patterns across each image. Camera presets tend to work well on similar photos, such as photos of people.

When you do not use a camera preset, the filter will scan your image (or selection) and determine potential areas needing correction by placing sampling regions in the highlight, midtone, and shadow regions.

Like other dialogs and tools, you can also save and load standard presets for this filter. When you load a standard preset, the filter will use the preset's dialog settings, but will still scan the image and place the three sampling regions.

Typical Uses for this Filter

Here are some scenarios in which this filter could be an ideal solution:

• For photos you know are going to contain excessive noise (such as a video whiteboard capture), use the filter with low settings to help make the overall image clearer without excessive blurring.

• For photos taken with normal settings yet still having image artifacts surrounding the subject area, use this filter to target just these key areas needing correction.

• For photos taken with the same camera that tend to have noise in the same area, use this filter to create a camera preset that can be applied to all images from the camera.

• For higher-end photography, use the options in the filter's Protect Image tab to specify the color ranges to preserve or discard.

• Lower-end cameras tend to produce more noise than higher-end cameras.

• Note that in some cases, using the JPEG Artifact Removal filter before using this filter (or instead of using this filter) can yield good results. Be aware also that the Digital Camera Noise Removal filter is not designed to remove moire patterns.

Accessing and Using the Filter

1. Choose Adjust > Photo Fix > Digital Camera Noise Removal.

2. Note the three crosshairs placed on the image preview in the Remove Noise tab (not in the normal preview area in the top half of the dialog). These represent noise samples (as determined by the filter) located in the image's light, midtone, and dark areas.

3. Click a crosshair to view its sampling region in the upper left preview window.

4. To move a crosshair, hold down the right mouse button and drag the crosshair to a new position. The sampling region will move accordingly.

5. To create more crosshairs, go to the left preview pane in the upper half of the dialog, and then drag the cursor over the areas you want to apply correction. A correction box will encompass the area you dragged, and in the Remove Noise section's preview box, a crosshair will appear over the area. (Note that you may want to maximize the size of the dialog and zoom in appropriately (in the upper left preview window) to help identify image areas with noise artifacts.) You can have a maximum of 10 sampling regions.

6. Avoid sampling an image edge (this will result in excessive smoothing), and avoid sampling pure black and pure white regions of the image.

7. To make a sampling region's box active in the upper left preview window, click its associated crosshairs in the Remove Noise section's preview box.

8. To remove a crosshair, go into the upper left preview pane and drag a corner of the correction box onto its diagonally opposite corner.

3. In the Remove Noise tab, set a level for the Small, Medium and Large details correction settings. These settings denote the amount of correction in its respective spatial noise band. Mark the Lock check box to adjust these settings in proportion to each other.

4. Use the Correction/Blend setting to determine the percentage of the corrected image to blend in with the original. Values range from 0 percent (no noise reduction) to 100 percent (full processing of the entire image), and the default is 70 percent.

5. Use the Sharpening setting to define the percentage (if any) of sharpening to apply to the image after the noise reduction is applied. The default value is 0 percent.

6. To save the current settings as a preset specific to this image and camera, mark the Camera preset check box, and then save the preset by clicking the Save button found in the Presets drop list at the top of the dialog. Note that when the Camera preset option is checked, the Presets drop list will only display previously saved Camera presets, not the standard presets.

7. To save the current settings as a standard Preset, uncheck the Camera preset option, and then click the Save button found in the Presets drop list at the top of the dialog.

8. Click OK to apply the correction.

Using the Protect Image Tab

For more advanced correction, click the Protect Image tab. The options in this tab allow you to define regions of color and texture that can be protected from noise correction. For example, you may want to protect skin tones in a photo from having any correction applied to them. You can define as many regions to protect as you like. To define a protected region:

1. Select the Protect Image tab.

2. In the dialog's upper left preview window, pan and zoom as necessary so you can view the region you wish to protect.

3. Hold down the Ctrl key and drag the cursor to over the region you wish to protect. Note that by holding down Ctrl you will not create a corresponding crosshair in the Remove Noise tab's Sampling Regions preview area.

4. In the Protect Image tab, the Hue and Range settings will reflect the area you sampled. Click here to see an example. You can manually adjust the Hue knob by dragging it inside the ring, or by adjusting the Hue and/or Range settings.

5. Optionally, you can drag any of the seven graph handles downward to progressively diminish the noise reduction (apply less correction/smoothing to that segment of the hue range). For example, dragging just the middle graph handle all the way to the bottom of the graph will completely suppress the midtone of the current hue range. Note that you cannot drag the graph handles laterally.

6. To completely remove all color adjustments (essentially starting over in this tab), click the Reset All button. To remove color adjustments for the current color range, click the Reset Current button.

7. Click OK to apply the correction.

Related Topics

Removing Artifacts from JPEG Images

Using the Chromatic Aberration Removal Filter

Improving Saturation

Improving Colors

Using the Fill Flash Filter

Using the Backlighting Filter