Photography 101 : What is ISO?
Knowing how the ISO setting work and what purpose it serves in your camera is crucial. Being one of the three pillars of the Exposure Triangle (the other two are a shutter speed and the aperture) ISO number cannot be undermined or disregarded. While the other two parameters are relatively easy two understand: shutter speed is the speed with which camera captures the light, aperture is the size of the hole through which the light is captured – the ISO number seems to be more mysterious.
It is not. The ISO parameter is actually really easy to understand. Let us explain it to you!
WHAT IS ISO?
ISO parameter is the only parameter is the triangle of exposure that doesn’t have mechanical nature. Instead it is controlled electronically and is related to changing the level of sensitivity of the sensor in the camera. The sensor is the most important part of your camera. It captures the light with each of its pixels and later creates the whole image. At times when there is not enough light to capture to get a bright enough photo, boosting the ISO number helps the sensor to capture more light…and more “noise”. In the video provided at the end of the article a good comparison is drawn where the camera relates to the light like a microphone relates to the sound. If you are trying to record the whisper on the microphone, you need to boost the sensitivity to make the whisper audible. With that you will hear not only the voice but all the background noise and a hum of electronics. The same goes for the camera. When you increase the ISO number (sensitivity) you can brighten up darker pictures but with more grain in it.
Take a look at the following picture:
Every camera has a “Base ISO”, which is the lowest ISO number you can set to produce the highest quality image without any adding any noise. Most of the cameras have Base ISO number of 100. And then it goes in sequence of geometric progression – 100, 200, 400, 800, 1600, 3200, etc. So each time you level up the number, the sensitivity doubles on the sensor.
For example, for the ISO 400 you double the amount of light captured compare to ISO 800.
ISO Speed Example:
ISO 100 – 1 second
ISO 200 – 1/2 of a second
ISO 400 – 1/4 of a second
ISO 800 – 1/8 of a second
ISO 1600 – 1/15 of a second
ISO 3200 – 1/30 of a second
So when do we use higher ISO?
WHEN YOU USE HIGHER ISO.
You should increase the ISO when there is not enough light for the camera to be able to quickly capture an image. So shooting indoors without a flash you might want to increase ISO to avoid introducing the blur.
ALSO, if you are shooting very fast moving objects, like running animals or sports, higher ISO would help to freeze the moment and get that money shot. However, be cautious of increasing your ISO too much and introducing unpleasant noise. Test your camera beforehand to see where the sweet spot is. Every camera is different. Usually full frame cameras let you shoot with higher ISO without any noise. Also, depending on how advanced the sensor technology is newer cameras with the same size sensor have higher ISO capabilities.
Take a look at the video below posted by Apalapse that explains the ISO in a very easy to grasp way!