One of the most significant advantages that modern cameras have over their film-based counterparts of days gone, by is their ability to change how sensitive they are to light with the touch of a button.
Back in the days of film you had to decide ahead of time whether you wanted to shoot at ISO (then called ASA) 100, 200, 400, or in extreme cases, 800. If you were going to take pictures outdoors, a roll of 24 or 36 exposure, 100 or 200 film would work fine, but woe betide the unsuspecting photographer who wandered inside a dimly-lit building with that same film still in his or her camera. To change sensitivity, and shoot in the new lighting conditions, you had to shoot the rest of the pictures on a given roll of film, remove it from your camera, and hope you brought some ASA 400 or 800 film with you.
Nowadays you just spin a dial on your camera to instantly switch between ISO values like 100 or 200, that work great in broad daylight, to ultra-high values like 6400 or 12,800, that would be positively unthinkable with film. It’s not all sunshine and roses though as one of the biggest issues with high ISO values is that of digital noise. Even the newest cameras produce pictures with noise and grain when shooting at high ISO values, but thankfully Lightroom can help mitigate some of the effects of this noise.
Shot at ISO 5000, the original image was too noisy for practical use. Lightroom enabled me to clean things up significantly.
To get started with the noise reduction options click on the Develop module, then find the Detail panel on the right side. Note: this process works best if you shoot in RAW, not JPG.
You will find several options that can seem a bit confusing and overwhelming at first. You can experiment all you want, by just moving the sliders around to see what effects they have on your pictures, but it also helps to examine each one individually, to know precisely what they do. You will also see the Sharpening options, which are related to noise reduction, but I’m not going to focus on them specifically just yet. Before you look at the sliders themselves in the noise reduction area, it’s important to understand the two types of noise that are produced when taking a picture, Luminance and Chroma.
Luminance noise
This kind of noise affects the brightness, but not the color, of individual pixels. If you had a picture of a dark grey piece of paper with a great deal of luminance noise it would appear similar to old-school television static with lots of light and dark fuzz.
Chroma noise
This shows up as oddly-colored pixels, scattered throughout an image, almost like someone has tossed a handful of red, blue, and green grains of sand at it. Lightroom calls this “Color” noise, but it’s just another term for Chroma noise.
Both types of noise are byproducts of how digital image sensors capture data, and while they can be corrected somewhat in Lightroom and other post-processing software, it’s almost impossible to completely remove noise from a picture while still ending up with a usable image. Lightroom does give you some tools to get your digital noise under control, and if you know what you’re doing you can get some fairly decent results. Using separate controls for luminance and chroma noise, in combination with some sharpening adjustments, can help you salvage what you may think is a useless picture. As an example, here’s a picture that I took at ISO 6400, without any noise reduction applied.
35mm, f/5.6, 1/60 second, ISO 6400
Not bad, right? If this is what ISO 6400 looks like, you might as well shoot like this all day long! Well, before you go and spin your ISO dial all the way up to Ludicrous Mode, you might want to take a look at the same 24-megapixel image zoomed in to 100%.
Ow, my eyes! The noise, it hurts! Not only is the picture full of color blotches, but shooting at ISO 6400 has resulted in an image that is far less sharp than it could be at a lower ISO. A great deal of color noise is evident on the torso of the figure, as well as the slanted lines on the left side, and you can see lots of luminance noise in the green letters on the right side too.
This noise is not always visible when you shrink your files down to share online, but if I were to print this picture it would look like my cat threw up on the paper. Lightroom can help us fix things, and a good place to start, in this case, is with the luminance slider at a value of 30.
Much of the black and white static has been removed, but there are still splotchy patches of color scattered throughout the image, which can dealt with using the color slider next. Before you start thinking that this is a magical cure-all for your noisy images, take a closer look at the picture. Much of the details have been lost, or blurred, such as the lines on the side, and the patchwork of the figure’s tunic.
You can mitigate these effects somewhat by using the detail and contrast sliders, but again the results are not going to be ideal. Detail acts as sort of a threshold control, allowing you to tell Lightroom what should be treated as noise and what should be left in. I usually leave this slider at 50 but you can experiment with it to get the results you need. The contrast slider helps bring back some of the edges that have gotten blurry, thanks to the noise reduction algorithm, and even though I have set it to 25 in this example, you can clearly see that much of the edge contrast is not as good as the noisy original. Move this slider too far though, and your photo will start looking fake and artificial, so you’ll have to find a good balance depending on your needs.
To continue with the noise reduction, the color slider can be used to get rid of the weird splotches of red, green, and blue, but again you are going to see some tradeoffs.
The results look fine at first, and you may notice that Lightroom automatically applies some degree of Color noise reduction (value 25) to every photo by default. This is because low-grade Color noise reduction is almost always good to have, and generally won’t result in too many tradeoffs for the image as a whole. In this case I used a value of 40, to show the effects a bit more. Even though the result is decent, you might notice something else that’s missing, if you look at the soda bottle label on the right-hand side. Compare it to the original picture and you will see that along with removing some of the color noise Lightroom has actually removed some color from the whole photo.
The Detail slider slider, similar to its counterpart in Luminance noise reduction, acts as somewhat of a threshold so you can tell Lightroom what is, and is not, noise to remove. The Smoothness slider is a fairly recent addition to Lightroom, and can be used to control what’s known as “low-frequency” color noise. Basically, slide it to the right to remove larger splotches of noise or to the left to keep these more intact.
Every time you use Lightroom’s noise reduction tools you will deal with tradeoffs, and one of the most significant of these is the overall sharpness of the image. Photos with more noise reduction will almost always be softer, particularly where there are sharp contrasting edges, and you can bring a bit of this back by using the sharpening tools.
Here’s yet another 100% crop of the image above with the same noise reduction employed in the previous image, but with added sharpening.
After a bit of sharpening, the detail in the lines on the left side has returned, and so has the texture of the tunic, but the lower-left corner is still a muddy mess of grey, whereas in the original noisy picture it was more defined. Here’s both the original and edited image side-by-side which might help you get a macro view of how these noise reduction and sharpening tools can affect a picture.
At first glance you might not notice too many differences, but one of the most glaring problems with the edited picture is the complete lack of texture on the wall behind the scene, as well as a smoothness to the plant that is almost unnatural. Here’s a side-by-side zoomed in to 100%.
Is it worth these tradeoffs to get a photo with less noise? That question can only be answered by you, but one rule of thumb I like to follow, is that a noisy image can be corrected and edited in postproduction, albeit somewhat imperfectly. A blurry image cannot be fixed.
So, if there is a situation in which I find myself having to choose between a faster shutter speed and higher ISO (i.e. more noise), or a slower shutter speed and lower ISO (i.e. less noise) I’ll usually err on the side of noise, if the slower shutter speed would result in an image that is too blurry.
I also make liberal use of my camera’s auto-ISO feature, which allows me to set a minimum shutter speed and a maximum ISO value. That way I can concentrate on adjusting the aperture to get the composition I want, and always know that my pictures will be free of blur, even if does mean there will be a bit of noise I have to clean up in Lightroom.
The light here was quite dim, which required a high ISO value. I didn’t mind a slightly noisy image that was sharp and in focus, because I was able to get rid of most of the noise in Lightroom.
One final note worth mentioning is you can also use Lightroom’s local adjustments like the Radial Filter, Graduated Filter, and Adjustment Brush to apply noise reduction in specific areas of an image only. However, this is a bit limited, in that these adjustments only perform luminance noise reduction, so you might still be left with some ugly colored spots, that can only be removed using the global adjustments in the detail panel of the develop module.
What are some of your favorite tips and tricks for removing noise? I’d be interested to hear any thoughts you have in the comments section below.
The post Tips for Removing Digital Noise in Lightroom by Simon Ringsmuth appeared first on Digital Photography School.
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