Whether you use an SLR, a compact or a smartphone camera, at a certain moment you discover disturbing dots in the photos. They are not noticeable in the mini screen of your device. If you look at the photo on the computer screen, you will see them. Where does that noise come from, how do you avoid it and what can you do with it?
Noise is what used to be the grain in negative films. In the days when we still put rolls of film in a camera, we could intentionally increase noise by using a black and white roll of film with a higher ISO (then called asa). Today, we can adjust the light sensitivity of the image sensor in the digital camera within certain limits. There are plenty of reasons to want as little noise as possible. We want cool, clear, sharp photos without interference. Digital noise does not look the same as old-fashioned grain and if you are unlucky, noise will cause color deviations. If there is a lot of disturbing noise, you can filter it out, but because of that processing you run the risk that the photo loses sharpness and that details are lost.
Less light, more noise
The tiny red, blue, and dark speckles that interfere with the photo’s details are referred to as noise. It always has to do with difficult lighting conditions and never with resolution. And often noise is simply unavoidable, because no camera is noise-free.
When the analog light (the photons) are converted to a digital signal (the electrons on the sensor), you risk noise. The sensor’s millions of light-sensitive pixels each receive a small portion of the light. And the more light that falls on an individual pixel, the better the result.
Higher ISO, more noise
In digital devices you can adjust the light sensitivity by setting the ISO value. When it is dark, the sensor sometimes does not have enough light to form a clear image. Increasing the ISO makes the sensor more sensitive to light.
If the camera is set to ISO 100 and you change it to ISO 1600, the camera will be four times more sensitive to light. Basically, the electronic signal leaving the sensor is amplified. Unfortunately, this amplification also creates more noise. Compare it with a sound system. The higher you turn the volume knob, the more noise you hear. If you amplify the signal by turning the volume knob to maximum without playing music, you will clearly hear the basic noise.
With short exposure times, the signal to noise ratio is low. If you work with a longer exposure time, the signal and noise will increase. Light areas are often less affected by noise than dark areas. It is therefore good to photograph with the lowest possible ISO value, taking into account that you will get a less sharp result under less good light conditions. Sometimes you have to be satisfied with a compromise, you go for a sharp photo with a little more noise or for a noise-free but blurred photo.
On smartphones
The standard camera apps of smartphones are aimed at simple operation. Even with the iPhone 12, the ISO on the regular photo app is not adjustable. The iPhone is always trying to shoot photos with a low ISO (minimum ISO 25) and a fast shutter speed, because a low ISO produces little noise and a fast shutter speed prevents motion blur. On iOS and Android, most competing third-party photo apps have a pro mode where you can set the shutter speed and ISO. With a paid camera app, such as Manual or Halide Camera, you can adjust the iso value, shutter speed, white balance and focus of the camera.
Sensor size
When two cameras have the same sensor size, the device with fourteen megapixels produces more noise than a device with ten megapixels. With small cameras in which increasingly compact sensors are mounted that have to deliver more megapixels, the risk of noise is greater. That is one of the reasons why an SLR camera takes better photos than a compact camera, the sensor is simply larger.
Noise canceling
Many camera manufacturers give their cameras the Noise Reduction function. This applies a noise reduction algorithm when a slow shutter speed or a high ISO value is requested. Do not expect miracles from this. Often this function does not remove all noise and the function also produces less sharp images. You notice that in parts with many details.
Monochrome or color noise
There are two types of noise. There is a colorless noise or monochrome noise that consists of grayscale. On a computer screen, that monochrome noise, also called luminance noise, usually looks much worse than it does on the printout. You will then see a disturbing salt-and-pepper effect. Color noise or chroma noise are colored irregularities. The red and blue specks are much more disturbing on the print.
In post-production
Actually, you can better apply noise reduction in post-processing. Getting rid of luminance noise usually comes at the expense of a bit of sharpness. If you tackle chroma noise, this will affect some colors. So it remains a balancing act, because by tackling the noise, the image softens.
Much depends on the purpose for which you want to use the photo. When you have a small image in mind, the noise is in any case less visible than when you want to make a large print. Programs such as Photoshop Elements, Photoshop and Lightroom have different filters to suppress both types of noise.
For example, when you Camera-raw at the Filters opens, you have three sliders: Sharpen, Noise reduction and Color noise reduction. This gives you everything you need to calmly find the balance between sharpness and noise reduction. It is important that you enlarge the image to one hundred percent in the view. This means that one pixel of the image corresponds to one pixel of the display. That is the only correct way to objectively assess sharpness and noise.
Free noise suppressors
Most serious photographers have decent software to manage and optimize their photo files. There are online solutions to suppress noise, but they have little or no control options. In addition, there are also freeware solutions such as NDNoise for Windows and macOS, but it is not user-friendly.
We tip as a standalone solution Noise Reducer Pro. The macOS version costs 1.09 euros and you can even use it as a plug-in for Apple’s Photos app. This product is free on Windows. Noise Reducer Pro is super simple. You load a photo and on the left you see the original file, on the right the optimized version.
You can zoom in steplessly or immediately press the button 100% use to assess sharpness. Then click on Car to neutralize the noise on the autopilot. Or you use the slider to find the right balance between sharpness and noise reduction. Then save the files as jpeg, bmp, tiff, gif or png. So this software does not support raw files.
Aging
So far we’ve talked about brushing away noise. To age photos, or to give them a certain authenticity, you can also add grain. Back in the day, before the days of digital photography, there was always a soft grain due to the chemicals needed to develop photos. Some photographers were even known for the typical beautiful grain in their work. How do you age photos and add grain? We show this simple technique in five steps that you can do in any photo editor.
We use the online editor for this Pixlr. You open the website Pixlr E and there you use the button Open image to select the photo you want to age. In the menu Adjustment you choose the assignment Desaturate. This removes the saturation of all colors so that it appears as a grayscale image, while still containing color information.
Sepia
To give the photo a typical sepia tone, go to within Pixlr again Adjustment and Color balance. You will then see three sliders. Here you have to in the tab Midtones the setting for Red increase and for Blue to lower. There is the sepia tone. Adjust these sliders until the shade is exactly the way you want it.
Vignette and grain
To apply the grain, use in Filter, Detail the assignment Add noise. Use the slider again to add a nice dose of grain (noise). The finish comes from a vignette, which is a discoloration at the edges.
In the same menu you will find the assignment Vignette. Dragging the slider to the left lightens the edges of the photo. If you drag the slider to the right, the edges become darker. We choose the first option.
