April 16, 2012

What is ISO in digital photography and when to select the right ISO

While operating the camera in manual mode you probably must have stumbled upon the term ISO. Mastering the use of ISO can significantly improve your digital photography skills. This post presents the concept of ISO in a very insightful way. Keep reading on…

What exactly is ISO ?

It can be considered as a unit of digital photography that measures the sensitivity of your camera’s optical sensor towards light. That is; for a higher ISO number, your camera will be more sensitive towards light and for a lower ISO number, your camera will be less sensitive towards light. Consequently, for a high ISO (more sensitivity towards light) the camera shutter will snap rapidly (allowing light to enter for a very small duration). In other words, high ISO results in short exposure time (ex – 1/400 of a second).
Similarly, for a low ISO (less sensitivity towards light) the camera shutter will snap slowly (allowing light to enter for a very large duration). As a result, low ISO results in
long exposure time (ex – 1/5 of a second).

Choosing the right ISO settings for your pictures

a) Light sensitivity point of view
Since an ISO number reflects how sensitive your camera is towards light, consider using a high ISO when shooting under insufficient or low light conditions. Similarly, consider using a low ISO when shooting under ample of light conditions. Use of a very low ISO must be avoided as this results in blurry photos being captured even with slightest of shake while holding the camera (Reason: Lower ISO results in longer exposure time)

b) Exposure point of view
While shooting a scene where you want to display motion in your photograph, consider using a low ISO (which results in longer exposure time and motion blur). For example; capturing motion of a speeding car, a drifting subway metro or anything which inspires you to capture the motion. Similarly, consider the use of high ISO when you want a still photograph without any motion blur. For example; while performing baby photography which involves a lot of rapid movements or any sports event where you want to freeze the motion.

Problems with Low and High ISO settings

Using high and low ISO has it’s own advantages and disadvantages. We have covered most of the advantages in the aforementioned paragraphs, now we will discuss some of the key disadvantages of using an ISO number which is set too high or too low in magnitude.

Too high ISO is the main cause of noise in photographs and too low ISO is the main cause of blur in photographs.

Possible solutions are:

1. To eliminate noisy effect due to high ISO – Use a high speed camera lens or use noise ninja application to eliminate the noise.

2. To eliminate blurry effect due to low ISO – Use a tripod coupled with remote controlled capturing (since under low ISO settings, even the slightest of shake while pressing the shoot button triggers blur)

ISO and noise example:

ISO digital photography 

ISO digital photography

low ISO    High ISO

For a DSLR camera, a change in ISO directly affects the exposure triangle where one has to readjust the other two parameters accordingly – Aperture and Shutter Speed.

Most of the photographers set their camera to auto mode where the ISO is automatically adjusted to an appropriate value in accordance to the scene being captured. ISO plays a very important role in digital photography and its appropriate use should be mastered for capturing amazing photos regardless of what the shooting conditions are !