# The five-minute guide to Noise Ninja

For first-time users of Noise Ninja, this section provides a tutorial introduction to the noise reduction workflow. While it does not cover Noise Ninja in depth, it covers the most important points, and it should be enough to allow you to start using the tool productively within a few minutes.

## The big picture

The general procedure for removing noise from an image involves the following steps:

> 1. Click on the Profile tab. Load or create a noise profile. A profile characterizes the noise in different colors and tones for a particular camera or image. Noise Ninja provides several methods for creating and loading profiles.
> 2. Click on the Filter tab and adjust the filter controls. The effects of filtering are displayed in the Preview window in the upper right portion of the user interface. There are a number of filter controls, though most of the time you will only need to use one or two of them.
> 3. Click on the Noise Brush tab. Paint on parts of the image that you want to protect from filtering. Sometimes, this can save a lot of time compared to tweaking profiles and filter settings. It is also easier than trying to do the same thing with selections and layer masks.

These steps are described in more detail below.

## When to apply noise reduction

As a general principle, you should apply noise reduction as early as is practical in your workflow — ideally, before other editing operations like tone adjustment, color balancing, sharpening, or resizing. Adjustments like these can shift pixel values and distort noise levels in unpredictable ways, and this can make it more difficult for Noise Ninja to remove the noise effectively. Sharpening and resizing, in particular, should be deferred until after noise reduction when possible. (Modest amounts of in-camera sharpening are usually okay, however.)

If you shoot RAW: If you use a raw file format like Nikon NEF or Canon CRW, it might require some experimentation to determine the best way to integrate Noise Ninja into your workflow, and you also might have strong preferences regarding how you want to use the different tools. Raw conversion utilities differ widely in the way they treat noise, and they typically allow numerous adjustments to be made during conversion. Some users apply minimal adjustments during raw conversion, apply Noise Ninja, and then make other adjustments using Photoshop or some other editor. This allows them to profile their camera and re-use the noise profiles for each image. Other users make arbitrary adjustments during raw conversion, and then they use the manual or automatic profiling tools (introduced below) to create a noise profile for each image.

## Getting around the user interface

Viewing windows: The Noise Ninja plug-in dialog has two viewing windows. The window on the left is the "main window", and it changes in size when you resize the user interface. The main window is used for navigation and for profiling. The smaller area is the "preview window", and it shows how the filtered image will appear.

The Navigation Tool: The two viewing windows are linked through the Navigation Tool underneath the Main Window:

When you activate the Navigation Tool, it displays a green rectangle in the main window which indicates the location of the preview window. You can drag the rectangle to change the location of the preview window. Likewise, you can scroll and zoom in the preview window, and the rectangle will move to reflect the new position or size.

Zooming and scrolling: You can zoom with a mouse wheel or with the zoom buttons in both windows. The preview window is limited to magnifications of 100% or larger, so that the filter preview can be recalculated quickly. You can scroll in both windows using the scrollbars or the Hand Scroll Tool. The Hand Scroll Tool can be activated by holding down the Spacebar. To use the Hand Scroll Tool, drag with the mouse in the window.

The menu bar: The menus at the top of the plug-in provide access to a variety of functions for configuration, saving and loading filter settings, viewing, and help. See, in particular, the Preferences dialog in the Noise Ninja menu.

The License dialog: Choose the "Install and view license" command from the Noise Ninja menu to install a license key or to view the license agreement. Certain features of Noise Ninja are restricted or disabled unless you purchase and install a valid license key. If no license is installed, filtered images will be overlaid with a gray grid pattern.

## Step 1: Create or load a noise profile

Before you can remove noise, you need to create or load a noise profile. A noise profile specifies how much noise is present for different colors and tones in an image. For instance, a noise profile can represent the fact that there is more noise in shadow areas than in highlights, or more noise in blues than in yellows. Noise levels vary from one camera to another, and they are also influenced by ISO sensitivity and other camera settings. Noise profiles are the key to getting good results with Noise Ninja, because they help the filter distinguish between noise and detail.

Click on the Profile tab to activate the Profile page:

Next, do one of the following to load or create a profile:

- Click the Profile Image button to create a noise profile automatically from the current image. This will scan the image and select regions that appear to be uniform and detail-free, and it will measure the noise in those regions. The automatic profiler is convenient, but be aware of its limitations. It can be fooled by some textures. Also, some images have too much detail in certain tones or colors, making it hard to create an accurate profile. You might obtain more consistent results, and your workflow might be more productive, if you profile your camera and reuse those profiles when you are filtering images. (See below.)
- Use the manual profiling tool Click the Manual Profiling Tool button beneath the main window:
  Using the mouse in the main window, select regions of the image that are uniform in color and tone, and which contain no important detail. Each time you make a selection, the noise profile graph is updated. You can delete a selection by control-clicking or command-clicking inside of it. Try to select several regions covering a range of tones and colors. At a minimum, try to select a region in shadow, another in the midtones, and one in the highlights. Also, try to make the selections as large as possible without including edges or other detail. At any time, you can switch to the Filter page and make adjustments to the filter settings. Click here for an example and discussion of manual profiling.

- Load an existing profile Choose the Open command from the Profiles men to load an existing profile. You can download profiles for many cameras from www.picturecode.com/profiles.htm You can also create your own profiles quickly and easily using a profiling chart that is included with Noise Ninja. Click here to learn how to profile a camera or scanner. Creating your own profiles allows you to customize them to your particular preferences regarding camera settings and other variables. It only takes a few minutes, and it is simple to do.

For the moment, you can just click the "Profile Image" button. When you have time, you are encouraged to read the chapter on noise profiles to learn other techniques that might be more productive or effective.

## Step 2: Remove noise

After you have created or loaded a noise profile, activate the Filter page. The filter uses the noise profile to suppress noise from the image:

Adjust the sliders until you like the results shown in the preview area. Each time you adjust a slider, the preview will be updated to show the effect of the adjustment. You can press and hold the View Original Pixels button on the right side of the preview window to see the unfiltered pixels:

There are three groups of sliders on the Noise Filter page. The Luminance group affects filtering of noise in the brightness component of an image. This component usually contains the most information in an image. The Colors group controls filtering of color noise, which is often the most displeasing noise. The Sharpness group enhances edge sharpness using an unsharp mask.

> Strength controls how aggressively the filter is applied. This is the control that you'll normally want to adjust if you don't like what you see in the preview window. If you move it far to the right, the image may look too smooth. If you move it to the left, it will look more grainy. Often, the most natural-looking results are achieved when you leave a modest amount of grain in the luminance channel.

> Smoothness increases or decreases the noise levels estimated by the Noise Profile. Usually the default setting is adequate, but if you see isolated specks in smooth areas, try increasing the smoothness setting to see if they go away.

> Contrast applies a scaling factor to edges, similar to an unsharp mask, but at several resolutions simultaneously. You probably won't need to adjust this in most situations.

> Sharpness amount and sharpness radius apply an unsharp mask to the filtered image. Some people prefer to set the amount to zero and do sharpening later in the workflow. However, even in that case, it can be useful to preview the sharpening effect to see how it interacts with the noise reduction. The unsharp mask calculation includes a halo suppression feature that helps to eliminate unnatural highlight artifacts that can occur when high sharpening levels are used.

Here is a simple strategy for adjusting the sliders that usually yields good results:

> 1. Move the Luminance Strength slider all the way to the right

> 2. Set the Luminance Smoothness slider to the lowest level that results in a smooth area without obvious speckling.

> 3. Reduce the Luminance Strength slider until you like the balance between noise reduction and detail preservation.

## Step 3. Refine results with the Noise Brush

After you have adjusted the filter settings, activate the Noise Brush page:

The Noise Brush allows you to partially or completely protect regions of the image from being filtered, by simply painting with a brush-like tool. The effect is shown immediately in the Preview window. The Noise Brush can be useful for preserving hair or fine texture that is close to the noise threshold. Instead of spending a lot of time tweaking profiles and filter settings to optimize results, you can often get the results you want with a few quick strokes of the brush. Also, using the Noise Brush is generally easier and quicker than trying to do the same thing using Photoshop selections and layer masks.

The Noise Brush creates separate masks for the luminance and chroma components of the image. Most detail in an image is contained in the luminance channel, while the ugliest noise is often in the chroma channels. By applying the Noise Brush only to the luminance channel, you can preserve detail while eliminating color noise.

The Mode radio buttons control whether the brush increases or decreases the masking effect when it paints. The Channel selector determines whether the brush is applied to luminance, chroma, or both mask components. The Brush traits controls change the size, strength, and style of the brush. The Erase mask button clears the filter mask for the entire image.

Tip: You can press the "." and "," keys on the keyboard to increase and decrease the brush size.

The mask created by the brush remains in effect until you erase it or quit the plug-in. So, you can go back and make further adjustments to the profile and filter sliders after using the brush.

## Step 4. Filter the entire image

When you are finished making adjustments, press the Okay button to apply the filter to the entire image. This will hide the plug-in dialog and execute the filter on the entire image. Filtering can take anywhere from a few seconds to several minutes depending on the speed or your computer and the size of the image that you are filtering.

## Beyond the basics

Once you've gotten comfortable with the basic operation of Noise Ninja, here are some other features and capabilities that you should explore:

- Pop-up help: Click on one of the Overview buttons to view pop-up help describing the most important tools and concepts in Noise Ninja. In addition, you can click on the "Whats This?" button and then click on an individual item in the user interface to view pop-up help for the item. The descriptions are generally more detailed than the tooltip help that displays when you hover the mouse over a control.

- Configuration The Preferences dialog in the Noise Ninja menu contains a variety of settings for controlling the performance, behavior and appearance of Noise Ninja.
- Actions You can use Noise Ninja as an action in Photoshop. This makes it possible to process multiple images automatically in a batch. Click here for details.
- Selections, layers, and channels Noise Ninja filters the layer or channel that is currently selected in Photoshop. In addition, it it only filters the area that is selected. In addition, you can use Photoshop's layer masks and brush tools to selectively mask noise removal after applying Noise Ninja to the entire image. (However, you might find that many of these tasks can be accomplished more quickly and easily using Noise Ninja's built-in Noise Brush feature.)