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The original title: "too much noise?" Ps stack noise reduction tutorials and principles, photographers are using lossless noise reduction skills! "

Noise is a thing that often deals with photographers, according to the current photography technology, as long as it is a photo, there must be noise, but it is a question of more or less.

Noise reduction has become a common link in the later stage, and noise reduction often encounters a problem: if you make great efforts to reduce noise, the noise will disappear, but the details of the photo will also be lost; if you gently reduce the noise, the details of the photo will be preserved, but there are still a lot of noise.

Today, let's learn a lossless noise reduction method often used by photographers-stack noise reduction.

Stack noise reduction ① first of all need to take multiple photos (about 4-9 photos, less effect is not obvious, too many are not very useful, I usually shoot 4-6 photos), the position of shooting can not be changed, if it changes, it should be aligned later. Let's take a look at the picture and see if there is a lot of noise.

② then opens ps, selects "File"-- "script"-- "load the file on the stack", clicks "Browse" to open a group of photos just now, and the photo is opened as a layer.

③ selects all layers, right-click, and convert them to smart objects, which becomes a layer.

④ selects "layer"-"Smart object"-"Stack Mode" in the menu bar, and for noise reduction, we have to choose the median or average.

The following picture of ⑤ shows the effect of the original image, the average noise reduction and the median noise reduction.

Let's take a look at the enlarged picture. The first picture is the original picture, and the second picture is the average denoised picture.

As you can see, the noise reduction effect after the stack is very obvious, and the most important thing is to retain the details of the picture. Because of these two points, stack noise reduction is favored by numerous photographers, especially in dark light photography such as starry sky photography, stack noise reduction is almost a necessary step to ensure the image quality of photos.

Stack noise reduction principle stack, literally, is to stack many photos together to generate a new photo. Noise is randomly generated and will appear anywhere in the photo. If four photos are taken, only one photo has noise in the middle, and none of the other three photos appear, and the noise will be weakened at the back of the stack.

Average stack: ① has 4 images, 3 are all white, and 1 has a black dot.

② uses the average stack, and the black dot at the back of the stack becomes 255255255100, then divided by 4, and eventually becomes 216. the black dot is weakened and closer to white.

02, median stack: ① has 4 pictures, which are all white, gray, gray and gray.

② now uses the median stack, and the point behind the stack becomes 100-150, then divided by 2, and the result is 125. when I look at it with the ps color picker, it actually becomes 126, which is not much the same.

In noise reduction, it is possible to use both average and intermediate values, and you can also compare them to see which is better. In addition to noise reduction, the median stack also has the function of eliminating debris. For the four images in the first group, if you use the median stack, the black spots will be removed directly.

This article is from the official account of Wechat: photography Research Society (ID:shoujiPhotography), by Zhang Xiaozhang.

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