Image noise comes in two forms – luminance and color noise. In a perfect world, image noise wouldn’t exist. But, unfortunately, it is an inevitable side effect of shooting with today’s digital cameras.
Managing image noise is an essential part of a photographers workflow. In this tutorial, we’ll be discussing the difference between luminance and color noise and some of the ways that you can reduce them in Photoshop.
There are two ways we can reduce noise in Photoshop: reduce color and luminance noise independently vs. reducing them simultaneously.
To reduce them independently we can use either the detail panel in camera raw or the reduce noise filter.
To reduce them simultaneously we can use surface blur filter, adjustment brush in camera raw, despeckle filter, or the smart sharpen filter.
Depending on your post-processing workflow and your photography needs you can decide which tool works best for you.
Luminance noise is derived from the (brightness) of the pixels within an image and is the most common type of noise found in digital photography. Luminance noise is directly related to image exposure and often appears as grain or specs. It is most common in underexposed images and as well as in pictures with high ISOs.
High ISOs are designed to create brighter exposures by amplifying the light information gathered by the camera’s sensor. Unfortunately, by doing so, it also increases the digital noise collected by the camera’s sensor.
Underexposed images have a low signal to noise ratio (SNR). Meaning it contains more noise information than light information. A lower SNR will result in an image with plenty of noise while a high SNR will result in a picture with little noise.
For the same amount of noise, overexposed images (high SNR), will appear to have less noise than underexposed images (low SNR).
Color noise, also known as chroma noise, is uneven color transitions in an image. It often appears as colors in areas that do not match the adjacent pixels. Color noise is emphasized and is more noticeable in the regions that are very bright or very dark.
Similar to luminance noise, underexposure and high ISO causes color noise. This type of noise is much more dangerous than luminance noise because it can render images completely unusable.
Identifying the Types of Noise in Your Photo
Before you begin reducing noise in your image, you must identify the location and type of noise in your image first. These two factors will determine your approach to noise reduction.
To locate the noise in your image, I recommend setting your zoom to 100%. Then, scan your photo for areas with visible noise. If you can see the noise present in your image at this magnification, you will need to do some level of noise reduction.
Keep in mind, that setting your zoom to 100% can sometimes make you over reduce noise. A more accurate representation of what your viewers will see is a magnification between 25% and 75%. When you’re applying noise reduction, try to switch back and forth between 100% and a smaller zoom setting such as 50%. Doing so will help you understand what your image will look like as a whole and help you avoid too much noise reduction.
In any case, once you have identified that there is noise present in your image, zoom in between 200% and 400%. At this magnification, it will be easier to determine if you have luminance, color, or both types of noise in your image. I also like to zoom in at this range when I adjust my noise reduction sliders. Doing so makes it easier for me to notice the change the slider is making on your image.
How Is Noise Reduced?
To reduce luminance noise, photoshop makes an image blurrier or less sharp. Color noise, on the other hand, is reduced by decreasing the saturation or smoothening the colors in a photo.
How Much Noise Is Acceptable?
Using noise reduction will reduce either image sharpness or image saturation. This trade-off means you must decide how much noise you are willing to accept relative to image quality.
Often, this will depend on your image’s final output. For example, the amount of acceptable noise will differ if you are printing your images compared to if you only plant to display them on digital screens.
It’s good to try and preview your image in its final form to determine the acceptable amount of noise reduction. Doing so will give you a better idea of the amount of noise that will be visible. After viewing the image in its final output, it will be easier to determine the amount of noise reduction needed.
If you can’t preview your image in its final output, a good rule of thumb is to apply noise reduction at a zoom setting of 100%. The amount of noise reduction used at 100% zoom should be suitable for most image outputs. That said, if you plan on displaying your images on large screens or as large prints, try setting your zoom greater than 100%.
Something to bear in mind is that some level of noise can be useful as it can add texture and depth to your image.
Reducing Noise When Shooting
- Stay away from high ISO’s. Noise signals are amplified and made more pronounced when using high ISOs.
- Ensure that your photo is exposed correctly. Underexposed images typically produce more noise.
- Keep your camera cool. If your camera is hot, it will produce more noise. “Heat” noise produces images with discolorations like color noise.
- Use faster shutter speeds. Longer shutter speeds expose your sensor to more light and more noise.
Taking these precautions while shooting is the best way to limit the amount of noise in your photos.
How to Reduce Luminance and Color Noise in Photoshop Independently:
There are two tools you can use in photoshop to reduce luminance and color noise independently: Camera Raw’s detail panel and the Reduce Noise Filter. These tools are unique and offer great control over the noise of your image. Use these tools if you want to apply different levels of noise reduction to the luminance and color noise in your photo.
Noise Reduction in Camera RAW Detail Panel
Step #1: Open Image
We will use the image below as our baseline photo. For our purposes, I boosted its exposure to 4.15 in Camera Raw.
Step #2 Open Camera Raw
- Opened in photoshop from the filter tab.
- Select Detail Panel
The detail panel has six sliders used for noise reduction: luminance, luminance detail, luminance contrast, color, color detail, color smoothness.
Step #3: Make Other adjustments
Other than noise reduction, there are other adjustments done in camera raw that can influence noise. For example, increasing the exposure of an image may also increase visible noise. Thus, before utilizing noise reduction, it’s best to first make adjustments on the other sliders such as exposure, shadows, and highlights.
Step #4: Zoom In
To correctly identify the noise present in the sample picture, I zoomed in to 100 %. At this zoom, noise becomes visible on the walls and roof of the building.
Step #4 Identify Types of Noise
To clearly distinguish the different types of noise within the photo set your zoom between 200% and 300%. If you look closely, you can see that this photo contains both luminance and color noise.
Now that we have identified the types of noise in the photo, we can decide which slider to use to mitigate the issue. I usually reduce luminance noise before I reduce color noise; this is a personal preference for myself and not a rule you must follow.
Luminance Noise Reduction Sliders
1. Luminance Slider
Luminance noise appears as “specs” or “grain” in an image. Increasing the luminance slider will make the “grain” less noticeable.
Keep in mind that removing luminance noise will also result in an overall softening of the image. Therefore, the higher the luminance slider the, softer or less sharp the image will be. At high levels of luminance reduction, your images will often look plastic due to lack of detail.
The image below shows the effect of the luminance slider. On the left side of the photo, the luminance value is set to 0, while the right side of the picture has a luminance value of 30.
Notice that applying the luminance slider has removed most of the visible noise. Also, notice that doing so reduced some of the details as well. In particular, the borders of objects are less defined and appear softer, seen on the shingles in the photo below. The edges between each shingle are blurry and less defined on the right side compared to the left side of the image.
The photo below demonstrates how the luminance slider affects image softness. The right side of the picture has a luminance value of 30, and the right side has a luminance value of 100. This photo shows us that at high amounts of the luminance slider, we lose most of the details in the image.
Keep in mind that there is no absolute value for the luminance slider. An appropriate value will vary based on image content. The degree of an acceptable level of luminance noise reduction will depend on the amount of luminance noise present in the photo, the amount of detail you are willing to forgo, and your overall goal for your image.
2. Luminance Detail Slider
The luminance detail slider is used to recover the details lost after adjusting the luminance slider. In particular, it acts as a threshold for the amount of noise reduced.
If you noticed in the photos above, as soon as we increased the luminance slider, the luminance detail slider automatically adjusted to a value of 50. That is because Photoshop applies a default setting of 50 for luminance detail slider for luminance values higher than o
At values above 50, the luminance detail slider will reduce the amount of blur caused by the luminance slider. Conversely, at values below 50, the luminance detail slider will increase the amount of blur caused by the luminance slider.
It is important to note that, while increasing the luminance detail slider will recover lost detail, it will also some add residual noise.
Let’s look at some examples. In the”before” side of the photo below, we have the luminance detail slider set at the default value of 50. On the right side of the picture, we have the luminance detail slider set at 70. Notice how the details on the left side of the image are much softer than the right side of the picture.
Let’s look closer and examine the image below. We can see that the left side of the image is blurrier than the right side. The details in the “after” photo are more defined. It is important to point out that the “after” image also contains more noise.
The luminance detail slider can balance out the amount of detail lost as you increase the luminance slider. It acts as a threshold for luminance values, giving you the ability to either add back or remove detail.
3. Luminance Contrast Slider
The luminance contrast slider adds contrast to your image and is used to add detail and texture back to your pictures. Note that increasing the luminance slider will also increase the presence of noise. It’s best to use small values for this slider.
If your image experiences a significant loss in contrast when increasing the luminance slider, rather than using the luminance contrast slider, adjust the contrast globally using a contrast slider. A contrast slider will have greater control and power than the luminance contrast slider. You can apply global contrast changes in camera using the contrast slider on the basic panel.
Color Noise Reduction Sliders
1. Color Slider
The color slider removes color noise by smoothing out discolored pixels. At high values of the color slider, saturation will begin to decrease.
Remember to reduce luminance noise before removing color noise. Doing so will make it easier to distinguish the color noise present in the photo and see the effect of the color noise reduction sliders.
Let’s look at some examples. The photo below has a significant color noise present. I have included some red circles to identify areas in the picture that have obvious color noise.
The smaller circle contains color noise in the form of a discolored pixel that does not match the adjacent pixels. The larger circle contains color noise in the type of patterned discoloration.
Now let’s see what happens once we adjust the color noise. The image below shows a “before and after” preview for the color noise adjustment slider. The before picture has a noise slider of zero, while the after preview has a noise slider of 95.
On the marked areas, there is a significant decrease in blotchy patches of color. You can see that the overall color of the image is smoother.
Note that using the color slider will cause colors to become desaturated. At lower levels of the slider, this effect is unnoticeable, but as you reach the higher value, the desaturation becomes more evident.
Be sure when you are adjusting the color slider that you find a balance between reducing the color noise and decreasing the saturation in your photo. Specific reductions in color noise may not be worth losing the saturation and vividness of colors in your photo.
2. Color Detail Slider
The color detail slider is built to preserve color details present in a picture. The default value for this slider is 50. Values above 50 will make details crisper and defined, while values below 50 will remove details and soften an image.
The color detail slider only has a significant impact if the image has a considerable number of edges. Increasing the color slider will desaturate the images.
Photoshop uses an algorithm to detect pixels with the most tonal difference, these tonal differences are called “edges.” The color detail slider will preserve details along these “edges”.
The color detail slider can help preserve edge details, anything above a value of 50 will increase detail, and anything below a value of 50 will decrease details. However, most of the time the default setting of 50 is usually a sufficient amount to restore loss detail and saturation.
In the example image below, I applied the maximum value for the color detail slider. Notice how the after the preview is more saturated. Also, notice how it has more refined edges than before image.
Something to keep in mind, increasing color detail can cause color noise to reappear. Color noise appears because the color is added back to the details and noise as well.
3. Color Smoothness Slider
The Color smoothness slider is used to smooth out areas in an image where colors are not uniform and spotty. Increasing the color smoothness slider creates smoother color transitions by blending adjacent pixels where color noise occurs.
Large values of the color smoothness slider will apply smoothening to more pixels. That is, more pixels will be blended when trying to adjust for color noise. The default setting for color smoothness is 50.
The color smoothness slider can be used to remove large areas of color noise in a photo. The action of increasing the value will smooth out any reaming color noise sections in the picture.
The photo we used above does not have much mottling or large sections of noise, so I will use a section from another photo as an example.
The photo on the left has no color smoothness applied, while the color on the right has color smoothness set to 90. All other settings have remained unchanged for these two images.
Although we have applied some color noise reduction, the photo on the left still has some large sections of discolorations of color noise. By using the color smoothness slider, we can smooth out these remaining sections and create an image that is more uniform in color.
Using a combination of the detail panel and adjustment brush allows you to apply selective noise reduction. For our image, I applied minimal noise reduction to the wall to preserve the detail and maintain the sharpness of the image. On the other hand, I applied ample noise reduction to the roof to remove any discolorations and improve the color transitions in the image.
Default Noise Reduction
Keep in mind that Camera Raw will automatically apply some small degree of noise reduction to Raw images. However, it does not apply to JPEG images because Photoshop assumes noise reduction has already been applied to JPEG images. The default noise reduction values are the following:
0- Luminance: 0
50 – Luminance Detail (when Luminance slider is greater than 0 otherwise 0.)
0 – Luminance Contrast
20 – Color
50- Color Detail
50- Color Smoothness
The Reduce Noise Filter
The Reduce Noise filter is another tool that you can use to adjust color and luminance noise separately in Photoshop. The Reduce Noise filter offers a basic settings panel and an advanced settings panel. Each panel offers multiple sliders that allow you to adjust the noise reduction in your image. The advanced settings will give you greater control of the color noise in your photo.
You can find the reduce noise filter under the same filter tab we found Camera Raw.
Basic Settings Panel
When you open the reduce noise filter you will see the basic settings panel by default. The basic settings panel has four sliders: strength, preserve details, reduce color noise, and sharpen details.
1. Strength Slider
The strength slider controls the amount of luminance noise reduction that takes place. Increasing the strength slider will reduce more luminance noise. A value of 0 will apply no luminance noise reduction to the image. Increasing the strength slider also make an image softer by blurring the details.
Let’s look at the images below to see the effect that the luminance slider has on an image.
The image on the left has a strength slider of 2 while the image on the right has a strength sider of 10. The image on the right has applied more noise reduction but is also much softer than the image on the left. If you look closely at the tree branches, you can see the ridges are less defined and harder to notice.
2. Preserve Details Slider
The preserve details slider will recover the detail lost when applying the strength slider. As you increase the preserve details slider, it will improve details and reduce less noise. At a value of 0%, no details are recovered, and the image experiences the full effect of the strength slider. At a value of 100%, you will recover all the details of your image, but little to no noise reduction will be applied.
Increasing the reduce noise slider will recover more details but will also add back initially removed noise. That said if we hold the strength slider constant an image with 30% for the preserve details slider will have more details and less noise reduction than an image with 20% for the preserve details slider.
The preserve detail slider is useful for balancing out the effect of the softness caused by the strength slider. Use this slider if you feel your image has become too soft. Adjusting the preserve details slider rather than strength slider will give you more control over the softness of the picture.
Let’s look at the images below.
The image on the left has a preserve details slider set to 0% while the image on the right has it set to 100%. At 0% the image preserves no details and the image is slightly soft. At 100% the image has all of its details, but the noise has also become visible again.
3. Reduce Color Noise Slider
The reduce color noise slider removes color noise from the image. Increasing the slider will reduce more color noise. It is important to note that as you reduce color noise, your image becomes desaturated. At high values, the desaturation can cause your image to appear dull and smooth.
The images below will show the effect that the reduce color noise slider has on an image.
The image on the left has a reduce color noise value of 0% while the image on the right has a value of 100%.
At 0% no color noise is reduced, and the colors remain unchanged. On the other hand, at 100% all color noise is removed and the color experience a high level of desaturation. At 100% the leaves in the image have become dull and have mostly blended into one single color.
The image on the left shows the dangers of reducing too much color noise. When adjusting this slider make sure that the reduction in noise is worth the loss in the vividness of your photo.
4. Sharpen Details
The sharpen details slider is a tool designed to sharpen your image at the pixel level. This slider is not necessarily related to noise reduction; it can make your details more crisp and defined. As you increase your slider the details in your image will become more defined.
This slider is useful for bringing back additional detail if you have a low preserve details slider selected. Unfortunately, when making an image sharper, it will also make the noise shaper.
Advanced Settings Panel
The advanced settings allow you to reduce noise on the different color channels individually (red, green, and blue).
The ability to reduce noise on each color channel separately gives you greater control over which colors will lose saturation.
The advanced settings panel offers three sliders: channel, strength and preserves details.
Before adjusting the noise in a channel it is good to first identify which color channels are producing the most noise. I recommend viewing your image outside of the reduce noise filter, with each color channel applied individually, to better identify the color noise. You can find the color channels for an image adjustment panel in photos.
Viewing your image with only one color channel applied will make it easier to determine which channel produces the most noise. It is likely that you will not have to reduce noise on every channel. Once you have identified which channel contains the most noise you can return to the reduce noise filter.
In the photo above I found the blue channel to have the most noticeable amount of noise while the other channels produced little to no noise. The blue channel has noise concentrated along the branches of the trees. Therefore, I decided to apply noise reduction on the blue channel to reduce the noise on my trees.
2. Strength Slider
The strength slider will function the same as the strength slider in the basic settings panel except it reduces color noise rather than luminance noise.
It is important to note that you will need to adjust the strength and preserve detail sliders individually for each channel. If you do not adjust them they will not be applied. The benefit of the advanced settings is that it gives you greater control of the color noise reduction.
3. Preserve Details Sliders
The preserve details slider will function the same as the preserve details slider in the basic settings panel. Use the reduce noise filter if you want to apply noise reduction along specific color channels in your image.
How to Simultaneously Reduce Luminance and Color Noise in Photoshop:
There are four tools that you can use to adjust luminance and color noise simultaneously: Adjustment Brush in Camera Raw, Surface Blur, Despeckle, and Smart Sharpen. Use these tools when you want to apply the same amount of luminance and noise reduction. They are typically much faster and easier to use compared to tools that offer independent noise reduction.
Surface Blur Filter
The surface blur filter offers a unique approach to noise reduction. It will blur the surface of objects while keeping the edges of objects crisp and defined. To do this photoshop uses its edge detection software to determine where a surface begins and where an edge begins.
Photoshop uses an algorithm to detect pixels with the most tonal difference, these tonal differences are called “edges.” Photoshop will only “blur” the surface enclosed by edges but not the edges themselves.
Surface blur offers two sliders that you can use to adjust the amount of noise reduction taking place in your image: radius and threshold
1. Radius Slider
The Radius slider determines the size of the blur that will be applied. As you increase the slider more pixels will be blurred and more noise will be reduced. Typically, the blur begins from the center of a surface enclosed by edges. As you increase the slider it will affect more of the pixels enclosed by the borders.
2. Threshold Slider
The threshold determines what the surface blur filter will consider an edge when applying blur to an image. Low threshold values, define edges as pixels with small differences in tones between them. High threshold values, on the other hand, view edges as pixels with a significant difference in tones between them.
Typically lower values will result in more edges and less blur while high values will result in fewer edges and more blur across the image. The amount of blur applied to an image will determine the amount of noise reduction. Higher amounts of blur will reduce more noise.
Let’s look at some examples.
The photo on the left has a threshold value of 7 while the photo on the right has a threshold value of 60. The image on the left has a smaller threshold and therefore a smaller amount of blur. This is because more edges are being preserved with a smaller threshold. On the other hand, the larger threshold value completely blurs the image. This is because at high threshold values few edges are preserved and more blur is applied.
Use higher threshold values to apply more blur to your image. If your image has lots of soft edges it is better to use small threshold values to ensure those edges do not get blurred over. Blurring over soft edges will reduce the amount of detail in your image.
When setting the threshold value set it to a value that will preserve the smallest details in your image, otherwise, your image will lose lots of detail.
Using the Adjustment Brush in Camera Raw for Noise Reduction
There are two ways you can use the adjustment brush tool to perform selective noise reduction. You can use the adjustment brush as your sole noise reduction tool or you can use it in combination with the detail panel.
The adjustment brush tool is located on the menu bar at the top of the Camera Raw window. Once opened, you will find a variety of sliders that you can use with the adjustment brush. For this tutorial, we will be focusing on noise reduction and size slider. These are the two sliders you can use to adjust your noise reduction.
1. Noise Reduction Slider
The Noise reduction slider has a default setting of zero. Positive values reduce the noise in your image, while negative values add noise to your image. When adjusting noise it is important to set all the other sliders to zero to ensure you are only adjusting noise and not sharpness or moire for example. Similar to the luminance and color sliders increasing the noise reduction slider to really high values will soften the details in your image.
2. Size Slider
The size slider is used to adjust the width of the brush which enables you to refine the application of noise reduction to your image. The more you increase the slider the larger the brush will become.
The major disadvantage of the adjustment brush is that you can not adjust the color and luminance noise separately. The slider will adjust both the color and luminance noise simultaneously. The adjustment brush also lacks control over the detail and contrast the detail panel offers.
Adjustment Brush Only
There are a few reasons to use only the adjustment brush to reduce noise. The first is when there is only a small region of your image that contains noise and you simply want to adjust a specific region of the photo.
The second is that you want to apply different noise reduction settings in different areas of your photo. The adjustment tool will allow you to do this easily and quickly.
To begin, select the adjustment tool and set the noise reduction slider to your desired value. The adjustment tool functions as a brush, allowing you to paint over the areas in the photo that you want the noise reduced.
On the image below, I applied two different noise reduction settings for the roof and for the wall. Each white pin represents different settings of noise reduction. Clicking on the pins will reveal where the settings are applied. The area where noise is reduced is represented by a white overlay over the image.
The images below will show the two different settings that I applied to the image. On the roof, I set the noise reduction slider to 45. On the wall, I applied I set the noise reduction slider to 20.
Detail Panel + Adjustment Brush
I will now show you how you can use the adjustment brush and detail panel together to reduce the noise in your image. This method is efficient when you are trying to remove noise from your entire image but would like to apply different levels of noise reduction in certain areas.
I will apply the same noise reduction sliders that I applied to my final image in Camera Raw. Then I’ll be using the adjustment brush to make selective noise reduction adjustments to the image.
Let’s say that after I apply the detail panel settings I feel that the walls on my building lost too much detail. The adjustment brush allows you to add some detail back while leaving the noise reduction on the roof unchanged. If we were only using the detail panel it would be harder to apply two different levels of noise reduction but with the adjustment brush, it is very easy.
Using the adjustment tool, we can specifically change the noise reduction levels on the wall.
I have applied a value of -75 noise reduction to the wall using the adjustment tool. This will add noise back that was removed by the detail panel settings. This will add more noise to the wall but also add some detail and texture back to the wall.
An important thing to realize is that if you use the detail panel after the adjustment tool, the settings you apply using the detail panel will only apply to the areas that have not been adjusted by the adjustment brush. Meaning the detail panel will only affect the areas were adjustment brush was not used.
Using the Despeckle Filter
The despeckle filter applies the same method of reducing noise as the surface blur filter. It detects edges in a photo and blurs the area enclosed by edges while maintaining the detail of the edges.
The despeckle filter is unique in that it does offers no adjustment sliders. This means that you have no control over the intensity or location of the noise reduction. While this can make noise reduction much faster it does offer less control.
Although the despeckle filter does not provide any adjustment sliders there are two other ways to adjust the noise reduction intensity of the despeckle filter.
- Use multiple filters. The more filters you use, the sharper your image will become.
- Use the opacity slider. By adjusting the opacity slider, you can reduce the effect of the filter you applied.
Let’s look at the images below to see the effect of the despeckle filter on an image.
The image on the left has no despeckle filter applied while the image on the left has the despeckle filter applied. While both images have retained their edges, the image on the right has some noise reduction. In particular, if you look at the trunks and branches of the tree they have less noise than the image on the right.
This filter is ideal for quick noise reduction while maintaining control over the edges in your photo. This tool often does not produce sufficient noise reduction but it ensures your images retains most of its details.
Using the Smart Sharpen Filter
The smart sharpen filter is primarily a sharpening tool but it does offer a noise reduction slider that can be useful. I will not discuss the sharpening sliders here but if you are interested read this article.
The noise reduction slider is on a scale from 0% to 100%. Larger values will apply more noise reduction than smaller values. Higher values of the noise reduction slider will make your images blurrier and cause you to lose details.
The image on the left has a noise reduction slider of 0% while the image on the left has a nose reduction slider of 100%. The image on the left has reduced nearly all the noise in the image but it has also caused the image to become soft. The noise reduction removed most of the details and texture that was originally on the branches.
The smart sharpen tool is based used when you need to reduce noise and sharpen your image simultaneously. Otherwise, this image offers little to no benefits over any of the other tools mentioned above.
In this article, we have defined the types of noise and how to identify those noise in your photo. More importantly, we looked at the two ways we can reduce noise in Photoshop: reduce color and luminance noise independently vs. reducing them simultaneously.
Reducing color and luminance noise independently is more time consuming, but gives you more control. To do this, you can either use the detail panel in camera raw or the reduce noise filter. You can also choose to minimize noise simultaneously. To do this you can use surface blur filter, adjustment brush in camera raw, despeckle filter, or the smart sharpen filter. Simultaneously reducing luminance and color noise is a much faster approach, but will give you less control over the process. Both methods are useful, depending on your post-processing workflow and your photography needs.