Why You Should Understand Exposure
Simply put, a photo is an exposure; the more you understand about exposure, the better your photos will be.
Once you start to grasp what exactly aperture, shutter speed and ISO do to a photo, you’ll be able to master their use correctly and creatively. This post will teach you how to create the right exposure for a situation and the negative consequences of each exposure factor.
I have also provided links with more detail.
How an Exposure is Produced
There are 3 factors that, combined, produce an exposure but with each one lies potential problems that you may have to face:
Firstly: the light passes through the aperture which determines how much light comes in.
Secondly: the shutter goes up to allow light onto the sensor/film.
Finally: the ISO determines how much to increase the exposure by.
I’ve written posts on all three of these factors that can be viewed by clicking the links but here’s some information to give you a basic overview:
All of this combines, producing an exposure like the one below:
The aperture is f/2.8 resulting in the shallow depth of field and soft feel to the photo.
The shutter speed is 1/100 of a second, allowing me to take the photo comfortably without motion blur.
The ISO is only 100 which has resulted in very little noise.
Getting the Correct Exposure Using Different Modes
Every modern camera has 1 or more light meter built into it, displayed on the screen similarly to the image above.
Different modes use this meter to automatically create the correct exposure; when the ‘needle’ is in the centre, the photo will be exposed correctly.
Aperture Priority will hold the needle in the centre (unless you’ve moved it manually) and as the aperture changes to allow more light in, the shutter speed changes proportionally to allow less light in, maintaining an even exposure.
The shutter priority mode does the same thing, just the other way round; as shutter speed is changed, aperture is automatically changed accordingly.
Manual mode allows you to change both aperture and shutter speed at the same time without conforming to a certain point on a light reader.
This mode is mostly used by more experienced photographers who want the extra control over a photo and know which settings to use in different circumstances. The light reader stills moves to indicate how exposed the photo will be, helping the photographer.
Different Exposure Conditions
Daylight: The photo below has excellent lighting conditions allowing you to use fast settings on your camera. It was taken at 1/250 of a second, an aperture of f/14 and ISO 100.
Night: Photos of scenes at night are best taken using a tripod, this allows you to create long exposures and play with the light without producing blur. The photo below was taken using a 30 second exposure, a wide aperture of f/4.5 and an ISO of 400.
Indoors: I regularly use a flash indoors, bouncing it off a wall or ceiling to create a more natural effect. The settings used below were 1/50 of a second, f/7.1 and ISO400 with a flash bouncing of the ceiling.
Event: Due to the lighting conditions at an event and inability to use flash, you usually have to boost your ISO. Artists tend to move around a lot on state so you have to use a fast shutter speed as well.
This results in a wide aperture with a narrow depth of field, a high ISO, and some pretty cool lighting conditions like in the photo below taken at 1/160, f/2.8 and ISO1600.