Photoshop lessons

Noise reduction in images using Photoshop

In this lesson we will consider such a popular feature of the Photoshop reduce noise in the image, including luminance noise, color noise and even jpeg artifacts. All this is possible with Reduce Noise, first introduced in Photoshop CS2. Please note that the filter only reduces noise, but does not remove it. Even such a powerful editing tool like Photoshop is not able to completely remove noise in the photo. Of course, often at low coverage, we have to shoot using high ISO values, so images are obtained with a large amount of noise. To remove the noise on pictures, use a Photoshop program, and also look at the effect of their removal.

Уменьшение шума на изображениях с помощью Photoshop

Take the image that was shot a couple of years ago during a walk in the Park Animal Kingdom in Disney World. The image was not edited, just applied the crop tool.
There are 3 types of filters to remove noise in Photoshop, and Reduce Noise is one of them. This color noise, usually composed of red, green and blue dots.
Photo taken with an inexpensive camera (“soap”), and if we increase the gorilla, you will notice a lot of red, blue and green colors in her fur, especially around the edges between the shadows and light areas:
Let’s see how you can reduce noise using a filter. To access the filter, go to menu “Filter”, select “Noise” and then click “Reduce Noise”:
Dialog box
Dialog reduce noise contains a large preview area on the left, so we could clearly see what actions we perform over the image (although we can also see what we’re doing in the document window), and various sliders and options along the right side of the window. Although it is not so obvious, the column on the right is actually divided into separate sections, each of which affects a different type of noise.
From top to bottom are the first two sliders: the power of the tool and preserve the information about the image (colored in green), they are used to remove luminance noise, which we will consider in the near future. Then comes the function of reducing color noise (yellow slider), which, as you may have guessed, reduces color noise. Below is the slider, we are not going to disassemble, the accuracy of the details (not the color slider), because it has nothing to do with noise reduction. The sharpness of the image, which is an analogue of this function is better handled by one of similar in Photoshop the sharpen filters, such as Unsharp Mask or Smart Sharpen (sharpen), so I would recommend lowering the sharpness to 0% Finally, the last paragraph – Remove JPEG Artifact – reduces the appearance of artifacts of jpeg compression:
To get the most reduced level of the noise filter, it is better to start off with the filter, so it had no effect on the image. But this option in Photoshop is not, so we can do the same thing, just drag all the sliders to the far left, which sets each option to 0. Also, make sure that you disable the option remove JPEG artifacts .
Navigation pane preview
To increase and reduce the image in the preview area, click on the plus icon ( + ) and minus ( – ) button at the bottom. The current scale is displayed between them. Click and drag in the preview area to move the image as needed:
Color Noise
The first type of noise that you want to check for and reduce is color noise (red, green and blue dots) in the image. Use the preview window in the dialog box to increase the area that contains the color noise. Start with the reduce color noise set to 0%, then slowly drag the slider to the right until the color noise will not fit into the picture. Preview the preview area while dragging the slider to find the results of your actions:
To quickly get access to view the original image and its changes, just click and hold the mouse button inside the viewport. This will show looked like the original version of the file. Release the mouse button to see the effect of noise reduction. In this case, the color noise looks satisfactorily with a reduced value of about 60%. We see in the preview that the red, green and blue dots have been removed. The values you ultimately use will directly depend on your image, so it is important to analyze the preview area at the time of his changes:
Luminance noise
Once you have taken care of color noise, it’s time to reduce luminance noise. Unlike color, which consists of different colored pixels, luminance noise contains dots of varying brightness levels (black, white and gray). I’m going to switch to another image, where the noise brightness easier to see. Usually, of course, working on the same image. Here is a photo shot in a dimly lit Museum with ISO 2000 with Canon 5D Mark II:
Despite the fact that the camera does a great job, it is impossible to keep noise to a minimum at such high ISO values:
Noise removal brightness – this is a simple two-step process, but remember that we must have realistic expectations from their pictures. In my case there is no way to make the shot at ISO 2000, similar to the clean and smooth as if it was made at ISO 100 or 200. All we can do is try to make the image better than it was originally. First, start with a power with values 0%, then slowly drag the slider to the right, analyzing the image in the preview area, until most of the luminance noise is removed. Press and hold down the mouse button inside the preview area to see how the image looked originally, then release the mouse button to see how to apply the filter. Once you have removed all the noise you can start to drag the slider to the right to return the details of the image. This is a great balance between noise removal and maintenance of parts of the picture, and values, which will vary for each image:
Additional options
If you think that noise reduction will not succeed without wasting a significant amount of image detail, try the advanced settings that will reduce the noise level on the basis of channels. First, drag the top slider back to 0, then select Advanced at the top right of the dialog box.
Most of the images consist of three color channels – red, green, and blue is a very common picture. One of these channels contain more noise than others. By reducing noise on the basis of channels, we can apply noise reduction on the channel that needs it most, leaving more image detail in the clean channels.
Switch the tab to Per Channel, using the option channels beside the preview of additional parameters. Adjusting sliders and selecting channels from the list, you can get acceptable results:
Once you have done all the operations in each channel, switch on the main controls by clicking on the General tab on the left, then try again to modify the sliders to adjust the result:
JPEG artifacts
Whenever you work with images in jpeg format, regardless of whether you are shooting in JPEG format on a digital camera, or the image was saved in this format, you will encounter artifacts of compression. They depend on the degree of compression, as well as how many times the image has been saved. Every time you re-save in jpeg, the quality gets worse. To reduce the appearance of compression artifacts, select Remove JPEG Artifact:
Make sure you have checked the image when you select this option, as it can lead to loss of too many details. As with the luminance and color noise, it’s always a compromise between noise reduction and preservation of image details. When you are finished, click OK in the upper right corner of the dialog box to apply all settings and exit filter to reduce noise.