# Introducing noise profiles

Before you can remove noise from an image, you need to load or create a noise profile. Noise profiles are the key to getting good results with Noise Ninja. A noise profile characterizes how noise varies with parameters like ISO, brightness, color, and resolution. For instance, they allow Noise Ninja to "know" that noise in an ISO 1600 exposure is very high in the shadows but low in well-exposed highlights, or that the blue channel in a film scanner has more noise than the green channel, or that luminance noise is stronger than chroma noise for a particular camera. Noise profiles thus provide crucial information for distinguishing noise from detail.

While profiles might sound a little technical, don't worry, they are very easy to work with. Usually, you only need to click a button or two to work with profiles.

## Loading an existing profile

If you already have noise profiles that characterize your camera or scanner, you can load one of them using the Open command in the Profiles menu. By default, noise profiles are stored in the NoiseProfiles folder in the Noise Ninja installation directory. You can change this location in the Preferences dialog.

You should load a profile that most closely matches the image that you are trying to filter. At a minimum, try to find a profile for the same camera model, image size, and ISO sensitivity.

> Note: You can download profiles for many cameras from www.picturecode.com/download.htm These profiles are typically created for "generic" settings for in-camera sharpening and other parameters. While they yield good results in many cases, if you use substantially different settings in your camera you might obtain better results by creating a custom profile. For instructions, click here.

> Note: Noise Ninja also includes an automatic profile loader that selects a matching profile when you open an image, based on annotations in the profiles and EXIF data in the image. Click here for details.

## Profiling your camera or scanner

If you don't already have a suitable profile for your camera or scanner, then you can create custom profiles yourself. It is easy to do and it only takes a few minutes. For instructions, click here.

## Creating a profile from a noisy image

If you don't have access to the camera that produced an image, or if you are simply in a hurry, then you can create a profile directly from the image that you are trying to clean up. This will often yield acceptable results, but it should not be relied upon too much, because it usually takes more time than loading a pre-defined profile, and because many images have too much detail to allow a good profile to be made.

### Automatic profiling

The easiest way to create a profile from the image is to click on the "Profile Image " button on the Profile page. Noise Ninja will automatically scan for detail-free regions in the image and measure the noise. However, the auto profiler is not infallible. It includes a number of heuristics for detecting detail-free regions, but some textures look like noise to it. So, the auto profiler may overestimate the amount of noise in the image. Also, some images have too much detail in some brightness or color ranges, so the auto profiler will not be able to select patches in those areas. In such cases, the profile may over- or under-estimate the noise in parts of the image that it cannot analyze.

There is also a Profile Chart button. This is recommended for use with profiling charts, which are used for creating camera profiles.

### Manual profiling

The second way to build a profile from a noisy image is to select patches manually. To do this, toggle the manual profiling button to the "on" position:

Use the mouse to select patches that do not contain any detail and which are uniform in color and brightness, Try to select enough patches to cover a range of brightness levels and colors. Noise Ninja will force each patch to be at least 16x16 pixels in size. Where possible, you should select patches that are larger, around 100x100 pixels. Avoid extremely dark or extremely light patches where clipping might have occurred. Click here for an example and discussion of manual profiling.

Control-click or command-click on a patch to remove it. Click the red arrow to reset the profile and start over.

You can also use the manual profiling tool to fine-tune profiles created with the automatic profiler.

## Annotating profiles

If you intend to reuse a profile with other images, it is a good idea to annotate it with the camera model, settings, and other information that might be relevant. Certain annotations are required if you wish to use the automatic profile loader. Click here for details about profile annotations.

## Saving a profile

Click on the Save button to write the current profile and filter settings to disk.