Have you ever noticed countless tiny colored dots in your photographs? If you have, it’s probably because you have (consciously or not) forced your camera into becoming more sensitive to light.
That feature or decision is managed via the ISO settings, because aperture is responsible for the amount of light hitting the sensor, and shutter speed determines how long light actually hits the sensor. ISO is the main reason for noise in our photographs, and today we’ll talk about how to reduce it.
There are ways to achieve this in-camera and in post-processing. But first, let’s define the difference between noise and grain, and how noise actually increases in our photographs.
Grain ≠ Noise
Unlike grain in film, noise is an undesired artefact created when we increase our camera’s sensitivity to light by increasing the ISO (100, 200, 400, 800, 1600, 3200, 6400, and beyond).
Film is manufactured by incorporating light-sensitive silver bromide crystals in very thin layers of gelatin. These light-sensitive crystals have pretty much the same “amount of sensitivity” but are embedded in different sizes. Finer crystals are used for less-sensitive films and rougher ones for high-speed films.
When light hits these crystals, they get dark and an image is captured. That's where graininess comes from, but it has a certain appeal. It is even desired by some film photographers. It imparts a gritty, rough look that is very appropriate to certain situations, like war or boxing.
So why is noise so unwanted? Because it is not a feature – it’s a flaw.
How ISO Affects The Amount Of Noise In Our Cameras
Cameras have become more and more powerful. Today, most are capable of rendering images at pretty bold ISO values with almost unnoticeable amounts of noise. This is one of the main reasons why the state of photography is so awesome right now. (Note: not everybody has access to such powerful cameras.)
If we consider all digital cameras, we can say that noise is the result two things: the size of each pixel in our camera's sensor, and an increase in ISO. Increasing the ISO usually generates noise, and it’s important to remember that digital cameras only have one sensitivity capability – “the nominal” one, which is the lowest possible value (usually 100 or 200). This is like the baseline.
Every time we increase ISO, the sensor becomes more and more sensitive thanks to electricity. The increase in electricity comes with static, and this is easily observable as noise.
Let me clarify this concept. When we increase the ISO in our cameras, we are increasing the signal's gain. This leads to an incremental rise in the noise associated with the signal. It’s like a radio tuned into a station, but with a little background noise due to overlapping frequencies.
If we raise the volume, we don’t actually improve the signal our antenna is receiving at that moment – we are amplifying the signal. Therefore, the background noise will only get louder. The same happens with our cameras.
Reducing Noise In-Camera
At this point, we hope you understand that noise depends on the camera's sensor. The best way to reduce noise is to use the minimum necessary ISO value to capture what we want, and only increase it when needed.
Some cameras have a built-in feature designed to reduce noise when shooting at high ISO settings or when shooting long exposures. Google “noise reduction on [your camera model]” to get the best instructions on how to achieve this with your camera.
Secure ISO values span from 100 to 800 on entry-level cameras, and 1600 in some more expensive ones. Recently I've seen good image results at ISO values of 3200 and even 6400, with almost unnoticeable noise.
You Can Reduce Noise With A Tripod
Before thinking of reducing noise in post-production, consider doing things in-camera as much as possible. Using a tripod will enable you to beat noise every time (unless you need to use a fast shutter speed).
One of the main reasons why we force ourselves into cranking the ISO is because our handheld capabilities aren't that impressive. If we need to take a photograph, we would rather take it at a high ISO setting than have it come out all shaky and weird.
Using a tripod (or any solid surface – the idea is to keep your camera still) will enable you to capture photographs at the lowest ISO setting (ergo, with no noise at all) and without the blurry results, you can get when shooting handheld.
Reducing Noise in Post-Production
Let's face it: sometimes we need to deal with complex lighting situations that demand us to sacrifice image quality to capture the picture.
If we get noise, there is a non-destructive way to reduce it, but it could lead you to some weird blurriness if you crank things way too much. Adobe Lightroom has a module (when developing a RAW file) called “Detail”. Here we can control Sharpening and Noise Reduction.
But let's just focus on noise reduction, since sharpening works by adding tiny dots to a RAW file. Noise reduction doesn't actually subtract the number of artefacts generated by the sensor. What actually happens here is that you can manage their structure and luminance qualities, as well as their color and even smoothness.
Each image is unique and will require some patience. The best way to do this is to enlarge your photograph to 1:1 to get a better idea of the results of moving these sliders. Some companies have been developing some impressive solutions for photographs that couldn't happen under regular situations and were shot at pretty high ISO values. Examples of these solutions are Photo Ninja and Topaz DeNoise
It’s important to understand that noise is created inside your camera due to electricity and the sensor's capabilities. If you know this, you'll expose in a smart way without having to sacrifice image quality with noise just to get the photograph. Please feel free to ask more about noise in our forum