What is ISO, Dual ISO, ISO invariance and where does all the noise come from?

ISO used to be fairly simple. In the film days, it was called ASA and was a measure of the sensitivity of that film to light. As we transitioned to digital and the years progressed, things have gotten a little more complex. In this video, the Syrp Lab team looks at ISO in the modern day. They take a look at features like Dual native ISO as well as discuss the issues around digital noise.

The video focuses on how ISO relates to video, as many modern ISO features are specifically designed for getting the best possible quality in your footage. But much of the information is still valid for photographers shooting still images, whether they be jpg or raw.

[Related reading: What is ISO invariance and why is it such a big deal?]

ISO should be an easy topic, but there are several different implementations for ISO these days, including analogue electrical processing, digital processing and dual ISO systems that are often a complete mystery. Essentially, though, ISO is some form of amplification of the analogue signal your sensor generates when light hits it.

Different implementations can have advantages and disadvantages. Things like ISO variance or invariance can have positive and negative implications. Dual ISO systems also have both advantages and disadvantages over other techniques. Explaining it out here in text can get very complicated very quickly, but suffice to say, the video does a great job of walking us through the differences between the systems with some great examples to illustrate the points.

Each of the different technologies has a different effect on the footage that’ll eventually come out of your camera. But what makes things complicated is that there isn’t always a clear winner. As I said, all technologies and implementations have their advantages and disadvantages. And those advantages and disadvantages will have different implications, such as dynamic range, or the amount of visible noise, for different people.

As to which one you should use… Well, watch the video and you’ll be able to make up your own mind.

Ultimately, no matter which method of camera you choose, ISO performance is increasing all the time. Every new generation of camera goes higher and/or gets a cleaner signal. Back in the early days of DSLRs, you’d be lucky if you could shoot higher than ISO400 and get an acceptable shot. These days, ISOs up to 12,800 aren’t uncommon with newer cameras to still get very clean images.

What will be acceptable tomorrow? Who knows, but with cameras and sensor tech now able to see in the virtual blackness, it looks like it’ll only keep getting better.