In the last posts we discussed three main factors that must be kept under consideration while adjusting exposure. The Exposure triangle refers to the mutual relationship between these three elements ‘ISO’, ’Shutter Speed’ and ’Aperture’. All the three elements control the amount of light entering the camera. All these three elements are related to each other i.e. if you change the value of one element you must adjust the other two in order to gain precise exposure. The below given image describes the exposure triangle:
ISO: The sensitivity of a camera to light.
Aperture: The size of hole located at the opening of lens near the camera sensor.
Shutter Speed: the time duration for which the shutter remains open.
An example –
Here’s a real world example: Consider a situation that I and my friend are at a beach and the sun is going down. My friend insists me to take his snap, so I take out my camera, adjust the camera setting with the shutter set 1/60th and I set the aperture to f/4 and take his snap. I look at the display screen, and after looking at his image I love the light and quality of image. However, I don’t like the depth of field – I can see too much of the background (the life guard station, other people, etc.). I want as shallow a DOF as possible, which means I need to increase my aperture setting. I open the lens wide open,to f/1.4. This is a 3-stop difference, which lets in 8x as much light to enter in the camera sensor. To compensate, to get back to the same EV that gave me such a pleasing image, I would need to increase the shutter speed by 3-stops – so I crank it up to 1/500th. I quickly take the picture again (that sun is going down)… and viola! I have my photo with the same EV that gives me that amazing quality of light AND with the shallow DOF so you can’t make out what’s behind my friend.
In the starting you might face some difficulties in adjusting all these three together but with time and a lot of practice you can overcome the situation and become a master of exposure. Few things that you must consider are that you must alter the setting of all the three elements together to maintain the proportion (changing aperture changes depth of field, changing ISO changes the graininess of a shot and changing shutter speed impacts how motion is captured).