Understanding ISO

25 / 05 / 2017


ISO refers to the Sensitivity of a camera sensor to available light.It is the third and final half of the exposure triangle ,the other two are aperture and shutter speed.Camera sensor is responsible for changing the sensitivity.Full form of ISO is International standards organization,and it is a standardized industry scale for measuring sensitivity to light.ISO was earlier know as ASA (American Standard Association) during film era. The option to control ISO is available in camera body’s.

Low ISO number means less sensitivity to the light.While higher ISO number increases the sensitivity of your camera.Camera has an image sensor which can change the sensitivity depending upon the availability of light.When you capture images with high ISO,you are able to capture images in low light situations without using a flash. Using Higher ISO number or High ISO sensitivity comes with at an expense-it can add grain or “noise” to your photographs. 

Look at the following Photographs :  

ISO Numbers

ISO numbers generally start from 100-200 (Base ISO).ISO increase in value in geometric progression (power of two).ISO sequence is : 100,200,400,800,1600,3200,6400 and etc.

Base ISO

Base ISO refers to the ISO number in which the camera sensor produce the photograph with the highest image quality without adding noise to the image.So one should always try to shoot with base ISO to get the highest image quality. Every DSLRs has it’s own Base ISO number. Some canon DSLRs have a base ISO between 100 to 200,Nikon DSLRs have base ISO of 200 whereas Sony has some camera’s with base ISO 400. 


When there is plenty of light,you should use lowest ISO possible to get the highest amount of detail and to have highest Picture quality.  In many modern full frame DSLRs the Lowest possible ISO number is 50.

Increasing ISO

When the light is not enough then you should increase ISO to quickly capture an image.While capturing images in indoors without a flash,you will have to increase your ISO to capture the moment and avoiding a blurry image.