Learning Basics of Exposure in Digital Photography


What is Exposure?

Light and exposure are at the very heart of photography. It is the light that creates your photo, and exposure decides the amount of light that should be there in your photo. Technically exposure is the amount of light reaching a photographic sensor. Being the most basic requirement for photography, yet even professional photographers struggle to achieve the perfect exposure.


Auto exposure is not always dependable. The metering of camera fails to give the desired exposure. Thus mastering the art of exposure is something that takes a lot of practice. Even experienced photographers always experiments with exposure as they go. It is time to venture out of the Auto mode on your digital camera and experiment with it’s manual settings.

Exposure Triangle

Exposure basically depends on 3 elements : Shutter speed, Aperture and ISO. All three elements are inter dependant. If we change one factor other should also be changed to maintain the constant exposure.


Exposure triangle to explain 3 factors

Shutter speed is the amount of time for which the shutter in front of sensor opens to allow the light from object pass. Aperture is size of opening of lens at the time of capture. ISO is a digital value, it is the sensitivity of sensor for incident light. All three elements all together decides the amount of light incident, also the depth of field and digital noise.

To explain these three elements in easier way, we can compare them with our eye or the window. Imagine your camera is like a window with shutters that open and close. Aperture is the size of the window. If it’s bigger more light gets through and the room is brighter. Shutter Speed is the amount of time that the shutters of the window are open. The longer you leave them open the more that comes in. Now imagine that you’re inside the room and are wearing sunglasses. Your eyes become desensitized to the light that comes in (it’s like a low ISO).


The great thing about digital cameras is that you can experiment with exposure as much as you want as digital cameras give feedback instantly. You can watch the image, analyse and improve your method to get perfect exposure. Yes, it’s true one can walk on his own way while learning the exposure, because metering or playback view is not always reliable. Metering tries to achieve the mid-tone which is not always correct method. Sometimes correct image can be over or under-exposed. I prefer to refer the “Histogram” of image to analyse the exposure. I’ll explain the Histogram in later posts.


Thus to master the exposure, we must learn about the 3 basic elements in details. Let us move towards the 3 kings of photography.

Shutter Speed




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