noise

Noise reduction (NR) in Lightroom 4 is absolutely great. When I used to use Lightroom 3, I had never relied on it for reducing noise in my photos since it was not that impressive in doing its job. I was using other noise reduction applications. But, adobe has done some serious changes in Lightroom 4. And one of the smart changes is in the NR section. Noise Reduction in Lightroom 4 There are two ways you can do image noise reduction in Lightroom 4: Global method. Selective method. This post is in two parts: Part 1: I will explain global and selective noise reduction methods, and I will walk you through the various settings of NR in Lightroom 4. Part 2: I will show you how to reduce noise in your images using Lightroom 4. And I will add some dos and don’ts of digital image noise reduction. What is Noise in digital images? Before getting into the noise reduction business, I would like to talk about few things on image noise. In the digital world, image noise is analogous to film grain. There are four different causes of image noise: Noise due to long exposure: In long exposure photographs, the noise appears as 'hot pixels'. The visibility of these hot pixels depends on the white balance setting or color temperature. Noise due to high ISO: Higher the ISO you use, more the image noise will be. In this type, the noise will be random and is mostly visible in the dark or shadow regions of the photograph. Banding noise or camera dependent noise: This type of noise is due to the brightening up of shadow regions by the camera. It is usually apparent in high ISO images. Noise from post processing: When you try to bring up the exposure of an under exposed photo, noise appears. This happens no matter what ISO you used. Another factor that causes image noise is sharpening. Sharpening increases contrast between adjacent pixels and over sharpening, especially a high ISO or long exposure, creates image noise. Do you 'really' need to remove noise? Noise is good. You don't have to reduce noise all the time. It preserves the texture in your photographs. So, my suggestion is, unless the noise is a distraction, you don't need to reduce it. Also, another thing you want to consider before going for noise removal is the output. I don't think you should do massive noise reduction if your sole purpose with your image is just digital sharing. Because, the information you see in a computer monitor and the information you see in a print is different. I mean, you need to do serious noise reduction if you are going to print your photographs. And you might want to use other applications or plugins for this purpose. Noise reduction in Lightroom 4 – A walk-through As I said before, you can do global and selective noise reduction in Lightroom 4. I will go through each of them and explain what the sliders mean. 1. Global Noise reduction Detail Panel2. Adjustment Brush for Selective Noise ReductionClick to enlarge Global Noise Reduction The noise reduction settings is located in detail box in the right panel of the develop module. 1. Loupe window2. Marker3. NR box Loupe window: This window is a preview of 1;1 magnification of a selected area of the image you are working on. Marker: The marker is used to show an area on the image in the loupe window. The noise reduction control sliders are -- Luminance, detail, contrast and color. To understand these sliders better, you should know the different types of digital image noises. Luminance noise: It is also known as monochromatic or grayscale noise. It appears as white splotches in the photograph. Luminance noise Color noise: It is visible as coloured speckles in the images -- especially in the dark or shadow areas in a high ISO image. Color noise Now, come to the sliders. Luminance: It reduces the luminance noise. The Default value is zero. Detail: It controls the threshold of the luminance noise. To put it simply, when you reduce the luminance noise, it makes the image soft. So if you drag the detail slider to the right, it makes the image less soft. The default value is 50. Contrast: it improves the local contrast thereby preserving the details. Default value is zero. Colour: Removes color noise. The default value is 25. Detail: It controls the threshold of color noise. When you reduce the color noise, it results in ‘spreading of colors or color bleeding. This slider preserves details in color edges. A higher value results creates small spots of colors. The default value is 50. Note: The best way to understand the effect of these sliders is to experiment with it. Selective noise reduction Sometimes, it happens that, noise is present only in certain areas on the image. So, why do you need to reduce noise of the entire image if it is present only in certain areas? There comes the need of selective noise reduction. Using Lightroom 4’s powerful adjustment brush, you can selectively reduce noise in an image. The adjustment brush is located at the top of the basic panel. The selective noise reduction is applied in two ways: You can adjust the noise slider to a positive value and painting in the areas of noise. You can apply the noise reduction globally, set the noise slider to a negative value in the adjustment brush, and paint the areas where you don’t need any noise reduction. Moving the slider to the right decreases the noise and moving it to the left increases the noise Unfortunately, there is no option to remove color noise in the adjustment brush. You can remove only the luminance noise with the adjustment brush. So if you want to selectively remove color noise, you should adopt the second method I mentioned above. This post will be continued in part 2. In part 2, I will show you how to remove noise using the global and selective noise reduction methods. Read: Lightroom 4 Noise Reduction Tutorial -- Part 2