How to remove noise from photos using stacking | Lesson | Photo, video, optics

Photo noise often becomes a big problem when shooting in poor lighting conditions without a tripod. Sometimes it simply reduces the quality of photos, making the picture less beautiful and «thoroughbred». There is a technique that allows you to make a clean picture at high ISO values. To use it, you will need continuous shooting, Photoshop and our instructions.

Situations where stacking can be used to suppress noise
What is stacking and how to remove noise with it
How to Reduce Drone Noise with Stacking
Noise reduction in smartphone photos
Other ways to get rid of noise. Pros, cons, comparison with staking
Results

If you have ever held a camera in your hands, you have probably encountered the problem of noise in the photo. Perhaps you tried to clean up noisy images in different ways. And you probably know that there are cases when the noise is so strong that when using noise reduction, small details disappear. For example, the eyelashes of a model or the texture of masonry on buildings.

Stacking noise reduction is interesting precisely because it allows you to save small details in the picture where they are lost due to noise. The classic ways to get rid of grain will destroy detail.

Situations where stacking can be used to suppress noise

For example, when you walk and see a beautiful sunset. Or the glow from the sun that has already set. And take it off hand only. There is no tripod, there is nothing to put the camera on (the frame deteriorates), there is nothing to rest against, so a slow shutter speed is not an option, everything is smeared. And on a short one, there is such a grain that even my mother is ashamed to show it.

In principle, you can use the same method to shoot a portrait in bad conditions. Especially when there is nothing to light a person with or the backlight spoils the atmosphere of the frame. The only thing is that the models in the frame also need to stand still while the shooting is in progress.

Another common use case for staking is shooting from a drone at dusk. You can’t put a drone on a tripod, and their matrices are usually small. So the picture is definitely noisy.

Most often, we encounter grain at high ISO values ​​\u200b\u200bwhen shooting in the dark. Each camera has its own maximum operating value, above which the pictures start to make a lot of noise. However, noise can appear not only when you shoot how blacks steal coal at midnight. Often when you try to stretch the shadows in post, they start making noise. This problem is especially noticeable if the shooting was a harsh light with pronounced highlights and shadows.

What is stacking and how to remove noise with it

Stacking is the combination of several frames taken one after another into one photograph. You can use this trick to get more dynamic range. A classic example is HDR.

Shooting in backlight, HDR was used to preserve details in both highlights and shadows / Photo: vk.com/yozheeg

We will use stacking to remove noise from photos. The principle of operation of this technique is as follows: for each pixel, the brightness value is averaged based on the values ​​from all stack frames. At the same time, the details present in all images remain, and visible noise is reduced.

To make it work, you need to initially shoot a long series. To effectively remove noise, you need from 7 to 20 frames. If you shoot less, the method will not work. If more, the load on the computer during assembly will greatly increase, and there will be no big difference in the quality of the final image.

How to shoot:

• enable continuous shooting;
• if possible, shoot in RAW (in JPEG, the built-in noise reduction often works, which will interfere with us);
• lock the exposure — use manual mode or the AE Lock button;
• frames can be made a little underexposed — this will save the highlights, and we will remove the noise in the shadows using stacking.

Preparing images for stacking starts in Lightroom. Raise Shadowsmute Highlights. Noise Reduction set to 10-15. Do not try to suppress all the noise at this stage. We copy these settings to all frames in the series and export the pictures in their original size in JPEG format.

We get the following result: an image with a good distribution of lights and shadows, but details are almost invisible in the shadows due to a large amount of noise / Illustration: Alisa Smirnova, Photosklad.Expert

You are now ready to upload your photos to Photoshop. To do this, go to the menu File / File — Scripts / Scripts and choose a team Load Files into Stack.

The required command is located in the menu section Scripts / Illustration: Alisa Smirnova, Photosklad.Expert

A window like this will appear, click on it Browse and select the files we need. There is another option: open all the necessary images in Photoshop in advance and use the button Add Open Files. But this method should be used only if you have a fast enough and large SSD and at least 32 GB of RAM.

Check the boxes so that Photoshop automatically aligns the files and creates a smart object / Illustration: Alisa Smirnova, Fotosklad.Expert

Click OK and wait for the layers to load and align. This may take several minutes.

Aligning images creates jagged edges that need to be cropped. Take this into account when shooting and do not crop too tightly / Illustration: Alisa Smirnova, Fotosklad.Expert

Let’s move on to noise reduction. To do this, open the menu Layer / Layers — Smart Object / Smart Object — Stack Mode / Stack Modeand choose one of the two modes — Mean / Averaging or Median / Median. There is a difference between them, which will be discussed later. For this image, select mean, though it doesn’t really matter to him. It could also Median.

The result is a stacking of 20 images, on the right is one of the original photos. As you can see, the noise has become much less, while the detail remains — you can see the wires, details of stucco and brickwork / Illustration: Alisa Smirnova, Photosklad.Expert

Choice between mean and Median it matters when there are moving objects in the pictures, such as cars or pedestrians. Chances are you will have them on some stacking frames and not on others. And it depends on the choice of mode what will happen to them in the final picture.

mean works like an arithmetic mean and just averages the brightness values. The light from the headlights of the car will become dim, but will still leave a ghostly trail in the picture.

Median works smarter — it just throws out big brightness drops. If there is no car in this place in 10 pictures, but it was marked in two, then these two pictures will not affect the final picture, and the headlight trail will completely disappear.

From left to right: one of the original stack frames with a car, Mean mode with a ghost trail, Median mode and a completely disappeared car / Illustration: Alisa Smirnova, Fotosklad.Expert

Therefore, stacking in this mode is also used in order to get a photo of “deserted” places, without passers-by or cars. If you take enough photos, even on a busy street, and stack them in Medianall moving objects will disappear.

How to Reduce Drone Noise with Stacking

This method of noise reduction is very useful for shooting from a drone. The cameras of quadrocopters, especially amateur ones, are very noisy at night due to the small matrix. Shooting at a slow shutter speed with a drone is also impossible — even with a light wind, the copter will sway slightly and blur the picture.

Drone shot at twilight, ISO 3200, 1/20 sec noticeable noise / Illustration: Alisa Smirnova, Photosklad.Expert

When shooting from the air, you should take more shots than you need for stacking. And accordingly, more than we would shoot on camera. You need to take at least 20 shots. Better even 30.

This is necessary, because due to the wind, some of them may turn out to be blurry or with a strong shift relative to the rest. Later, you can view them on the big screen and leave a dozen suitable for staking.

Noise reduction is done in the same way as when shooting on camera.

Left — original shot, right — stacking 10 frames, Mean mode. There is less noise, small details are much more visible — the seams between the tiles, balcony railings, wires / Illustration: Alisa Smirnova, Photosklad.Expert

Noise reduction in smartphone photos

You can also use stacking when shooting on your phone. There are some peculiarities here, because by default phones shoot in JPEG with a non-switchable built-in noise reduction. Of course, you can install a special application and shoot RAW, but then working with such pictures goes the same way as with frames from a DSLR or mirrorless camera.

Most modern phones have a night camera mode, which is essentially stacking — the phone takes several shots and combines them to reduce noise and get a photo with balanced highlights and shadows.

Shot in night mode on Redmi Note 8 Pro / Illustration: Alisa Smirnova, Fotosklad.Expert

Let’s take a closer look at the picture and compare the result of night mode and stacking.

Photo on Redmi Note 8 Pro. From left to right: the original frame for stacking, a shot in Night mode on a smartphone, a stack of 20 frames in Mean mode / Illustration: Alisa Smirnova, Fotosklad.Expert

The original photos are quite noisy, there is both brightness and color noise (which is not surprising for a shot at ISO 6640 and a small telephone matrix). The night shot looks nicer, and the noise on it is almost not noticeable. But the noise reduction worked quite aggressively, and along with the noise destroyed the seams between the boards, paving stones and other details. But staking worked well here, retaining much more details.

Other ways to get rid of noise. Pros, cons, comparison with staking

The best way to avoid noise is to shoot without noise. The landscape in the evening should be shot from a tripod: this way you can set the minimum ISO value and get a clean picture.

A shot from a tripod at a slow shutter speed, there is no noise even when approaching. Exposure 10 seconds, ISO 200, F8 / Photo: vk.com/yozheeg

Such a picture quality will beat any noise reduction methods, including stacking. But this approach is not applicable always and everywhere. For example, you won’t be able to shoot at slow shutter speeds and low ISOs:

• in a museum where you can not use a flash or put a tripod;
• when shooting from a drone in the evening;
• when you just don’t have a tripod with you.

Okay, no tripod. Or there is, but the picture is still noisy — you shoot, for example, on a phone, action camera or other device with a small matrix. You can go the other way: shoot a noisy image without any stacking and try to clean it up in post-processing.

There are different ways of noise reduction. Almost every camera and phone has built-in noise reduction, you can get rid of noise using Lightroom, Photoshop or additional special plug-ins.

Let’s try to reduce the noise in a picture taken with an Olympus E-M1 mark2 at ISO 6400.

JPEG directly from the camera, the result of work inside the camera noise reduction. Noises are not very noticeable, details are also gone, there is practically no information in deep shadows / Illustration: Alisa Smirnova, Photosklad.Expert

Now let’s develop RAW and work with noise. At the same time, we will make our picture more interesting — we will slightly raise the exposure, pull up the shadows and dim the lights. Set up noise canceling.

Noise reduction settings are medium — we will get rid of noise in this image in Photoshop, using the DFine plugin and using stacking / Illustration: Alisa Smirnova, Fotosklad.Expert

And while Lightroom is open, let’s look at its capabilities in the fight against noise. We reduce sharpening, increase noise reduction — the result is no worse than in-camera noise reduction.

Noise reduction using Lightroom. Noises are not very noticeable, detail is not high, when developing RAW, we managed to pull out some information from the shadows / Illustration: Alisa Smirnova, Photosklad.Expert

Now open Photoshop. To begin with, we decided to try to remove noise on one of the test images using the DFine 2 plugin.

DFine 2 is one of the additional paid Photoshop plugins from the popular Nik Collection plugin collection.

Application of DFine 2 with automatic settings. The result is even more interesting — the sign on the light side of the building is almost readable / Illustration: Alisa Smirnova, Photosklad.Expert

Now let’s get rid of the noise by creating a stack of 20 frames in Median mode and compare the results.

From left to right: stacking noise removal, DFine 2 removal, Lightroom noise removal / Illustration: Alisa Smirnova, Photosklad.Expert

As you can see, our method did not fail here. The sign is read much better (you can even make out that this is Lenin Avenue). General details above. And, most interestingly, there were details in deep shadows that neither Lightroom nor DFine could return. This is not surprising — in a single picture it is impossible to separate the details from the noise when their intensity is the same. Noise cancellation is not smart enough to tell them apart. But stacking copes with this: the details are the same on all stack frames — they remain, the noise differs from frame to frame — they are averaged and disappear.

Results

Cleaning photos from noise using stacking is, of course, not a panacea. In order to use it, you need to initially withdraw in a special way with the expectation of future staking.

But this technique is worth learning and having in your arsenal. It is easy to implement when shooting, does not require any special skills or gadgets. There are situations in which it can be used to take a clean and technical shot in difficult conditions without a tripod or fast optics.