Many images not only have the need for sharpening, but many have pattern reduction needs that supercede the sharpening demands.
When to Perform Noise Reduction and Sharpening
The workflow order of sharpening is easy: you should always perform this task at the end of your workflow. This is because sharpening reduces the range of tonal values that are available for editing functions.
Noise reduction should occur early in the workflow process. If the noise patterns are severe, you should perform noise reduction right after you resize/resample an image. Noise reduction, unlike sharpening, tends to enhance the range of tonal values available in an image, thereby providing more data for image editing. You certainly want to remove any unwanted patterns prior to any cloning and retouching, because this will only spread the unwanted pattern, which in turn might be further increased by the printing process. As a general rule, always remove unwanted patterns early in your image-editing workflow.
You will often perform noise reduction and sharpening enhancements on the same images, but you should always apply noise reduction first. When you apply noise reduction, you will want to be cognizant of how much the noise reduction is softening the overall image, especially the highcontrast edges. Be thinking about how you can minimize this and return some of the focus of the image by sharpening prior to printing. Removing a pattern in an image means softening. Photoshop offers many softening tools, including obvious ones such as the noise reduction methods found under the Filter --> Noise submenu. Photoshop’s Blur filters can also be used effectively as smoothing, pattern reduction tools. If you choose to use the Blur filters, you should use them with restraint, because they can quickly oversoften an image. Sometimes, as with the descreening project featured later in this chapter, you may want to use the noise and blur tools in concert. With practice you will become familiar with how each tool softens an image, and learn which tools to use where and when.
To remove noise without oversoftening an image, it is important to understand that in many cases, the noise may be concentrated in one channel (often the Blue channel). In the beach image, the three channels reveal the noisiness of the image in composite RGB view. Now activate the Channels palette (Window --> Channels) and click each of the three (Red, Green, and Blue) channels. Carefully view the background sky and beach. You will clearly see that most of the noise is indeed in the Blue channel. In a case such as this, you will want to focus your pattern reduction on the Blue channel. When you can focus your softening on one channel, you can push that channel pretty hard in terms of softening to make sure you remove all the noise, without oversoftening the image. This is because the other two channels hold the focus in the image together. You will find that even if you have only one channel that is fairly clean, it can often be enough to retain the overall sharpness of the image. After noise reduction is applied, you can then follow along with some sharpening to help boost the image focus (review the descreening example later in this chapter for a lesson in sharpening the Luminance channel in Lab mode, which can also help retain image focus).
Creating Duplicates and Maintaining Untouched Originals
Here is a really good habit to adopt: As soon as you open an image, reduce the onscreen dimensions of the untouched original image and place it in one of the corners of your monitor (type F/Ctrl+–), so that you can refer to it as you work. Then make a duplicate by choosing Image ➢Duplicate (you can create a keyboard shortcut to regularly accomplish this). This duplicate will be your working copy. This process both retains and protects the integrity of the original image, and keeps it onscreen for comparison purposes. This is a very useful habit to adopt for all your projects.
Lab Mode
Lab mode, like RGB, is a three-channel mode for color images. However, unlike RGB, Lab separates all the tonal values (Luminance/Lightness) and places them in one channel—the L, or Lightness, channel. By doing so, it allows you to apply a variety of neutral adjustments, such as blurring and sharpening, without any danger of affecting the color or chrominance values.
When to Perform Noise Reduction and Sharpening
The workflow order of sharpening is easy: you should always perform this task at the end of your workflow. This is because sharpening reduces the range of tonal values that are available for editing functions.
Noise reduction should occur early in the workflow process. If the noise patterns are severe, you should perform noise reduction right after you resize/resample an image. Noise reduction, unlike sharpening, tends to enhance the range of tonal values available in an image, thereby providing more data for image editing. You certainly want to remove any unwanted patterns prior to any cloning and retouching, because this will only spread the unwanted pattern, which in turn might be further increased by the printing process. As a general rule, always remove unwanted patterns early in your image-editing workflow.
You will often perform noise reduction and sharpening enhancements on the same images, but you should always apply noise reduction first. When you apply noise reduction, you will want to be cognizant of how much the noise reduction is softening the overall image, especially the highcontrast edges. Be thinking about how you can minimize this and return some of the focus of the image by sharpening prior to printing. Removing a pattern in an image means softening. Photoshop offers many softening tools, including obvious ones such as the noise reduction methods found under the Filter --> Noise submenu. Photoshop’s Blur filters can also be used effectively as smoothing, pattern reduction tools. If you choose to use the Blur filters, you should use them with restraint, because they can quickly oversoften an image. Sometimes, as with the descreening project featured later in this chapter, you may want to use the noise and blur tools in concert. With practice you will become familiar with how each tool softens an image, and learn which tools to use where and when.
To remove noise without oversoftening an image, it is important to understand that in many cases, the noise may be concentrated in one channel (often the Blue channel). In the beach image, the three channels reveal the noisiness of the image in composite RGB view. Now activate the Channels palette (Window --> Channels) and click each of the three (Red, Green, and Blue) channels. Carefully view the background sky and beach. You will clearly see that most of the noise is indeed in the Blue channel. In a case such as this, you will want to focus your pattern reduction on the Blue channel. When you can focus your softening on one channel, you can push that channel pretty hard in terms of softening to make sure you remove all the noise, without oversoftening the image. This is because the other two channels hold the focus in the image together. You will find that even if you have only one channel that is fairly clean, it can often be enough to retain the overall sharpness of the image. After noise reduction is applied, you can then follow along with some sharpening to help boost the image focus (review the descreening example later in this chapter for a lesson in sharpening the Luminance channel in Lab mode, which can also help retain image focus).
Creating Duplicates and Maintaining Untouched Originals
Here is a really good habit to adopt: As soon as you open an image, reduce the onscreen dimensions of the untouched original image and place it in one of the corners of your monitor (type F/Ctrl+–), so that you can refer to it as you work. Then make a duplicate by choosing Image ➢Duplicate (you can create a keyboard shortcut to regularly accomplish this). This duplicate will be your working copy. This process both retains and protects the integrity of the original image, and keeps it onscreen for comparison purposes. This is a very useful habit to adopt for all your projects.
Lab Mode
Lab mode, like RGB, is a three-channel mode for color images. However, unlike RGB, Lab separates all the tonal values (Luminance/Lightness) and places them in one channel—the L, or Lightness, channel. By doing so, it allows you to apply a variety of neutral adjustments, such as blurring and sharpening, without any danger of affecting the color or chrominance values.
Reducing Noise and Artifacts in Photoshop
![Reducing Noise and Artifacts in Photoshop]()
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