So you have your camera, but you want to get out of full auto, and make your pictures look spectacular. There are a few things you need to know, Composition and exposure are the main ones. In this guide I’m going to walk you through the basics of exposure. To do this we first must know three key elements which help determine your exposure, These are;
- Shutter Speed
- Apature
- ISO
Getting the perfect exposure is a balancing act between these three variable.This might sound difficult but as you progress through this guide, it will become easier to understand. I will teach you some technical terms which photographers use, fear not! These terms are used by every photographer and will make perfect sense when I explain them. Before we dive into the list above, I’d like to explain the concept of stops of light. You may have heard this term before and you have most likely heard photographers using it. A stop of light is half or double the amount of light being captured. I will explain this in context with the list above.
1. Shutter Speed.
Shutter speed is exactly what it says, it is the speed of the shutter. The shutter is a curtain that sits in front of your cameras image sensor or film. When you press the button to take a picture, this causes the shutter to open which allows for light to hit your cameras sensor, after a short period it closes again, stopping light from hitting your sensor or film. The length of time the shutter is open is called the shutter speed. It is measured in seconds or fractions of seconds. You can have a slow shutter speed such as 30s, which allows a lot of light to hit your sensor or film, or you can have a fast shutter speed such as 1/8000th of a second which allows very little light to hit your sensor or film.
A secondary effect of shutter speed is motion blur, A slow shutter speed will have more blur in the final image and a fast shutter speed will have less. Below from left to right is a fast to slow shutter speed image.
A stop of light in terms of shutter speed, is either halving the shutter speed for half the light, e.g. 1s -> 1/2s
Or doubling the shutter speed and doubling the amount of light, e.g. 1s-> 2s
2. Aperture
Aperture is the size of the opening at the front of the lens. The size of the aperture is measured in ƒ-numbers or ƒ-stops, I’m not going to go into the complex maths involved in finding this number, but I will explain the basics. A wide aperture is denoted by a small number and a small aperture is donated by a large number, below is a graphical representation of different apertures.
Apature is used to control the amount of light entering the camera, wide apertures such as ƒ1.4 will allow lots of light to enter the camera, and small apertures such as ƒ16 will allow only a tiny bit of light into the camera.
A secondary effect of aperture, is what is called depth of field, this is the amount of area of your photo that is in focus. A wide aperture like ƒ1.4 will give a very shallow depth of field, with very little of the image in focus and a large aperture such as ƒ16 will give a large depth of field with a large area of your photo in focus.
A stop of light in terms of aperture is a bit more complicated then shutter speed. Below is a list of full stop apertures starting with the smallest aperture, to the widest. Each number doubles the size of the opening as you go down the table, allowing a stop of light extra into the camera.
3. ISO
ISO is how sensitive to light your camera sensor or film is to light. The lower the ISO the less sensitive the camera is, and the higher the ISO the more sensitive to light your camera is. This is great now days with digital as we can change this at anytime to allow us to shoot with faster shutter speed, smaller apertures, both or even the opposite and lower it so we can shoot with slower shutter speeds and wider apertures. I’m sure you have all heard of film grain, this is like little specks on your image. This is normally caused by your ISO. A low such as ISO 100 has little to no noise while as you go up to higher iso’s you will see some to a lot of noise, e.g ISO800 or ISO1600.
Smilar to shutter speed the stops of ISO are either half or double the ISO number, so ISO200 is twice as sensitive as ISO100 and will capture twice( one stop) more light, and the opposite is true.
The key to getting the correct exposure is to balance these three variables, seems daunting but you only need to use two of these at a time. Put your camera into auto, Check what ISO your camera sets itself too, now change it back to manual, set it to that ISO, Now we only have to worry about shutter speed and aperture to get that correct exposure, we have a tool built into to our cameras to help us do this. This tool is a light meter, you may find this on the back of your camera’s LCD, a top LCD and you will always find it in your view finder.
The light meter allows us to see if the image is under or over exposed. If it is under exposed you can either slow the shutter speed down, open the aperture or a combination of each till the meter is centred meaning the image is going to be properly exposed, if this fails, try increasing the ISO.
If the meter shows that the image will be over exposed, you can make the aperture smaller, speed up the shutter or a combination of both till the light meter is centred, if this fails similar to the under exposed we can change the ISO, but this time we must decrease the ISO.
The more you get out and shoot trying different combinations of ISO, Shutter speed and Aperture the more you will learn to create the vision you want, and knowing how to control each variable is a key skill.