Shooting indoors or at night can often result in lots of noise. Even camera's that handle high ISOs well will have noise at super high ISOs. The good news is that Lightroom is one of the best tools to reduce the noise in your photos.
The Detail Panel
The Detail Panel is where we are going to do all our noise reduction. At the top of the detail panel, you will see a little preview box that is zoomed in to 1:1 over an area of your photo. This panel also handles sharpening. We will skip over that section and focus specifically on the Noise Reduction section of this panel.
TIP: Make sure you are zoomed into 100% as you make these adjustments as you can much better see the noise and changes you are making at 100%. Zoom out at the end to ensure that your subject hasn't gone too plastic and fine tune those sliders there.
Luminous noise is the speckles or grain that you see in your image. To reduce this noise in your image, slide the Luminous slider to the right. Be careful not to move it too far. Too much moving of this top slider will also make your subject begin to look overly smooth and very plastic. I rarely move this slider above the mid 20s.
The Detail slider is where you preserve details in your image. Since the Luminous slider works by blurring the noise a bit, the detail slider will help to preserve some of that detail from the blurring. Moving it to the right will bring back some of the details. I typically move this slider somewhere above 50.
The Contrast slider helps to preserve some of the contrast that is also removed by the Luminous slider. Moving that up a bit will bring back some of the contrast that was lost. Generally I move this somewhere in the 10s.
The other type of noise that you'll often see in high ISO images is color noise. This includes the little flecks of random colors that are introduced into the image and are much more prevalent in the shadow areas and darker high ISO images. Lightroom does an amazing job of removing these random color flecks from your image.
You will not need to slide the Color slider very far as it works quickly to reduce the color in images. Often just somewhere in the teen numbers will be plenty.
The Detail slider works very similar to how it worked in the Luminous section. The difference is that this slider starts in the middle. Slide it to the right to preserve detail and to the left to blur more of the details. Generally, I am moving this slider a little to the right.
The Smoothness slider will determine how much smoothing goes on in the image as the noise reduction is applied. Slide it to the right to increase increase the smoothness in your image and to the left to remove some of the smoothness that has been applied. Generally, I am moving this slider a little to the left.
Black and White Images
For images that have been shot in very low light situations, I love to change them to black and white. The same concepts above apply to black and white images. However, you will not SEE the color noise involved in the image because the color has been removed. Still play with this slider when reducing noise in black and white images as you will likely still see some improvement as you make these adjustments.
Allison Wheeler made a wonderful video for us all about noise reduction. Watch her make these adjustments to some of her images.