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Our smartphones have come a long way in reducing noise in photos. Before sharpening your photos, your noisy photo may benefit from noise reduction. In this article, I will cover two photo editing apps that I use, Snapseed and Adobe Lightroom mobile.
What is noise?
There are many different types of noise. The most visible noise is the random variation of brightness or colour information in images. These often appear as salt and pepper specks in the shadows or as bands of shadows. Some degree of electronic noise is present in any electronic device that transmits or receives a signal. An example of this is the background hiss you may hear in your audio system.
When you sharpen an image, it also sharpens the noise significantly degrading your image quality.
The other most common issue is pixelation noise and jpeg artifacts. This is due to insufficient image information/resolution for the required output. An example is cropping in tight and zooming in. It is also due to down-sampling an image or excessive editing.
Why does it matter?
When you sharpen an image, it also sharpens the noise degrading your image quality.
Noise can be desirable, adding an old-fashioned, grainy look - reminiscent of early film. Lightroom mobile has a Grain slider inside the sharpening tool and Snapseed even has a grain filter!
How do we reduce noise at capture?
There are many causes. The biggest factor for us mobile photographers is a high light sensitivity (ISO).
1. Manual control of the camera
Keep the subject and smartphone in fixed positions. Next, reduce the ISO number to the lowest setting and adjust the shutter speed (Sec) to the desired brightness (exposure).
2. Using a long exposure camera app
These apps blend many images and produce one final image. The most common type of noise is randomly positioned throughout each image. The more images that are 'averaged' the more uncommon placements of noise are averaged out.
In the above visual, I stacked 5 images on top of each other using the Adobe Mix app. The method selected to blend each image on top of the one below was the blending mode Difference. The resulting image keeps the difference between the base and top image pixels (all the dots in our image).
JPEG Vs DNG file format
The advantage of the DNG file format is the smartphone does not apply its own photo editing to produce the saved (output) image. As creatives, we then have complete control to use every pixel of data. The disadvantage is all the incredible computational photography advantages is bypassed.
The disadvantage of Jpeg is the file format is the "lossy" compression algorithm that discards information to save space. On most occasions, this compression takes an 8x8 block of individual pixels (dots) and makes it one dot. The result is a loss of sharpness and around high-contrast edges. This is due to approximating and smoothing the intensity of the transitions between colours and tones.
Wow, that was a lot of technical stuff!
My preference is the automatic processing the Jpeg file format does for me. Less editing and technical stuff mean I can concentrate on composition and photo intention. You can make an image look sharper in editing without requiring all the original information.
The process of noise reduction smooths the dots of colour and tone in your image, reducing sharpness. The goal is to reduce noise and retain as much sharpness as you can in the image.
In upcoming lessons, you will learn new techniques most professional photographer are not even aware of!
Noise reduction trick inside Snapseed
Snapseed does not have a noise reduction tool. However, understanding the process of noise reduction, you can replicate it using the existing Details tool (covered in lesson 4.1).
We need to smooth the image while retaining as much sharpness as we can.
Locate and use the Details tool?
Tap on the word Tools or the pencil edit icon > Details
Noise reduction inside Adobe Lightroom
One of the great advantages of using the Sharpening tool inside Lightroom is the Masking option. You can avoid enhancing the details in the flat, smoother and darker areas of the image where the noise and artifacts like to hang out!
Also within the Details section are two noise reduction tools - Noise Reduction (luminance noise) and Colour Noise Reduction.
Colour noise reduction
My editing process typically involves colour noise first. You can see this when the blotchiness has random colour. A more technical term is mottling artifacts.
First, move the smoothness to the right then adjust the Detail slider to recover any details (fine lines) lost. It is a real balancing act between the two sliders. You will rarely need to go above 25 in Smoothness.
Now you have three sliders to balance!
You will need to zoom in to see the effect of your adjustments then zoom back out again to make sure it still has a sense of realism.
The Contrast slider protects the contrast in the edges of the objects in the photo. Details is adjusted to bring back details lost when adjusting the Noise Reduction slider. Again, it is a balancing act.
Tap on the preview window outside of the actual image to fill the screen without distracting menus.
Tap and hold your finger on the image to preview the image before making all the Detail adjustments.
Swipe your finger on the zoomed-in image to navigate to another area of the image.
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