In very basic terms, ISO is the level of sensitivity of your camera to available light on the sensor. It has a very simple understanding of ISO, it’s not a rocket science. Lower the ISO number (e.g. 50,100), its represent less light sensitive and a higher ISO numbers (e.g 1200, 1600) increases the sensitivity of light to your camera.
A component of your camera which can change the sensitivity is known as “Image Sensor”, which is one of the most expensive and important parts of your camera body. I can say it’s a heart of any camera.
If you are from old days of a film camera, ISO (or ASA) was the indication of how sensitive a film was to light. It was measured in numbers, most you must have observed at 100, 200, 400 and so on. The lower the number the lower the sensitivity of the film and the finer the grain (picture quality) in the photo you are taking. In Digital Photography ISO measures the sensitivity of the “image sensor”. The principle is same as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain(picture quality).
Typical earlier days ISO/ASA was compared with our candle lights, 1 ISO/ASA = 1 Candlelight, means 100 candles can lighten up 100 ISO/ASA light power.
Typically ISO number increases in a geometric value of into power of two, that means you can see the value increase from 50, 100, 200, 400, 800, 1600, 3200, 6400 & so on, depends on camera model and available facility on it. That means ISO 100 and 800 has a difference of 8 times sensitivity between these two settings and which means, it requires less time to capture an image on camera image sensor.
To make it easy; sensitivity can be described as :
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 = 1/16 of a second
ISO 3200 = 1/32 of a second
Here is a simple way to understand this numbers. At ISO 100 if I need light to capture image is 1 second, at ISO 3200 takes just in 1/32 second. That means higher ISO, higher shutter speed to capture an image. This is just a simple Mathematical calculation, please just don’t go by that. Higher ISO value adds digital noise to your image as well. Digital noise means grains in your image.
Now the question will come up in your mind when to use low ISO and when high.
Right time for LOW ISO (Decrease value):
I must say in normal shooting condition please stick to basic ISO of your camera, means 50 or 100 whatever is available. Which helps to create the best image with most of the details with a high quality of an image. If you are in dark or low light conditions to use low ISO, your camera needs more time to capture an image and moving object might create blur or a ghost image as a result.
Right time for HIGH ISO (Increase value):
It’s a time to increase ISO when you find that your camera is not getting enough light, or you might need to capture object with ultra-fast (with high shutter speed) Or you don’t want to use flash in such conditions. Before you increase ISO just, be aware of side effects, high ISO means more noise (digital noise), be careful before increasing ISO value just like that.
What is my take away from this article?
Basically, all new digital camera is smart enough to understand ISO level and you also get option “Auto”. And you also can set limits with your shutter speed, mostly I set to Auto and let the camera decide what kind of ISO it needs for image and I work on an object or a picture without much worry. That doesn’t mean I don’t fix ISO, do when I know my “Auto” setting is not giving me desired result what I looking for.
The key point to keep in mind while working on ISO:
Touching ISO means you are playing with a core part of your camera. Keep in mind ISO is tricky setting and before taking any picture, make sure you have right ISO set on the camera, the moment never waits for you. I learnt this in a hard way after spoiling many pictures, means at the end of a shoot to find that I have forgotten to check what ISO setting & left their camera on in their last shoot. There’s nothing worse than thinking you’re shooting at an ISO of 100 only to find you forgot to switch it back from 1600. To help with this always check your ISO setting before starting to shoot – but also try to always switch it back after a shoot.
A solid understanding of ISO will help you make smart decisions about how to set your camera. And that, in turn, will lead to better pictures.