Exposure Compensation

Ashok Kandimalla has been in the photographic field for over three decades and has extensive experience in both film and digital photography. Being an electronics engineer by profession and a photographer, he possesses a unique and deep insight into the technical aspects of digital photography and equipment. He has published more than a 100 articles on photography and some of his writings have also been published in the well-known international magazine Popular Photography. An avid collector of photographic books and vintage cameras, Ashok has a keen interest in the history of photography and a passion for sharing his knowledge on photography through teaching and writing. He is the only Indian photographer to be featured on the Nikon Centenary website. He is presently working as a Management and Engineering consutant. He can be reached at [e-mail].

- Ashok Kandimalla

From the simplest point and shoot to the most advanced DSLR (or an MLC) there is probably no camera in the world without some form of exposure compensation control. This is perhaps the most extensively used feature by all advanced photographers. Yet it can be tricky to understand how exactly it operates. This article aims to go deep into this feature and help readers get a comprehensive understanding. Let us start by recalling a few fundamentals.

To begin, exposure is the right ‘dosage’ of light to create an image with the maximum number of tones recorded. The job of the exposure is to control the light falling on the sensor and thus bring it within the recording range. This is very similar to the way how iris in our eyes regulates the light reaching the retina. Exposure can be considered to have three components - Shutter speed, Aperture, and ISO. Though it is often mentioned that these three form the so-called ‘exposure triangle’ (Picture 1) there is a difference in the way they behave. The first two together, either individually or together regulate the amount of light that reaches the sensor. The ISO on the other hand is an electronic function that defines the amount of light needed to make a proper exposure, with higher ISO values needing less light. There is also a mistaken notion that ISO changes the sensitivity of the sensor. It does not as that is fixed once the sensor is made. Increasing the ISO in your camera essentially enhances the gain of the internal amplifiers thus making the signal from the sensor stronger with the adverse side effects of increased noise and reduced dynamic range.