Welcome to the Lights Film School video on ISO
Before we begin, let’s talk about what ISO is.
An ISO setting is the digital equivalent to Film’s A.S.A setting. Simply put, your ISO is your camera’s sensor sensitivity to light. The higher the ISO speed, meaning the larger the number, the more sensitive your sensor will be to light. The lower the number, the less sensitive your camera’s sensor will be to light. Your ISO setting combined with your aperture and shutter speed work together to give you your correct exposure.
However, when shooting in low light environments, better light sensitivity doesn’t come without a cost. Let’s take a look at this image at night in the park for example. As you increase your chip’s sensitivity to light you also increase the amount of “noise” in your image. “noise” is a sort of digital degradation within your image. It manifests itself in different ways in different cameras but it has a general characteristic as a sort of digital grain.
Besides your ISO setting, heat and sensor size also impact the amount of noise in an image. There are also different types of noise. For example, “fixed pattern noise” may be caused by long exposure times. Next, “Random noise”, which is seen in this image, is the type of noise most filmmakers struggle with, and is caused by high ISO speeds. Lastly, “banding noise” which plagues some cameras more than others, may be caused when the shadowed parts of the image are lightened.
All of these different types of noise look slightly different but they all share 1 common characteristic: They degrade the picture quality of your video. Noise is usually identifiable by a bunch of flickering or moving pixels on a surface that should otherwise appear smooth.
Again, look at our park image and notice how “noise” manifests itself throughout the different parts of the image.
Now let’s look at two shots with roughly the same exposure but shot at two different ISO speeds. Notice how there is virtually no difference between the image on the right and the image on the left.
But let’s look again, and closer this time, at what happens when we zoom into the image on a larger screen. The image on the bottom-left shows a noise free image. However, the image on the bottom-right is suffering from some pretty sever noise. However, if you look above at the images those close-ups were taken from, both images seem almost identical and noise free.
This is because image noise is often subtle when viewed on small LCD screens on the back of your camera. In fact, it’s often not until you’re watching the footage on a larger monitor that you uncover the problematic issue of noise and image deterioration.
Of course noise has an impact on the small videos as well, but for any filmmaker out there with television or theatrical ambitions ISO and noise will become increasingly important for you to be aware of. As soon as you enlarge your image noise will become substantially more noticeable. So be aware of your ISO settings when you’re capturing your raw footage to avoid problems later on in editing.
ISO ‘sweet spots” are another thing you may need to be aware of for your specific camera brand and model. For instance tests, show that different ISO speeds handle noise differently. For example, on some Canon DSLR’s there is actually less noise in the ISO setting of 160 than there is in the ISO setting of 100. These are technical details you need to look into for your own particular brand of camera..
Every image has noise, but for the most part in lower ISO images, noise will appear less noticeable. The Signal to Noise Ratio (SNR or S/N) is the universal way of measuring the relative amounts of signal and noise in your shots. High ratios will have very little visible noise while low ratios will have lots of noise.
Noise reduction software also exists to help you get rid of unwanted noise. For example, Neat-Video offers a great solution for both MAC and PC users. Again, it’s advisable to get as strong of a raw image as possible, but noise reduction software such as Neat-Video can help you salvage otherwise useless footage. Again, here is our footage shot at a high ISO setting of 6400 and here it is again after being run through Neat-Video noise reduction software.
One of your goals before you hit the record button should always be to ensure you obtain the best image quality possible using the lowest ISO possible.