The Exposure Triangle - Photography Basics
A beginners guide to the light and the exposure triangle
PHOTOGRAPHY BASICS
For many photographers learning to use manual mode, aperture, ISO, and shutter speed, can be very confusing. This is especially true when referring to the relationship between the three. To make things worse, there are names like 'f stop' or 'stop' that are used interchangeably but mean different things all together. My aim is to take out a bit of the confusion and hopefully help you better expose your photos.
The Exposure Triangle
Aperture, ISO and Shutter Speed are the three sides that make up the exposure triangle. They are the balancing act that produces the exposure of your photo. To produce the best exposure, you have got to have a good understanding of what each does and how they work in relation to one another. If one of these variables changes, at least one of the other variables must also change in order to maintain the same exposure.
Stop of Light
The first thing we need to know is what a stop of light is, as it will help better understand exposure. A stop of light is the doubling or halving of the amount of light. Meaning, an increase of one stop of light is double the amount of light in the photo, while dropping two stops of light is cutting the exposure to a fourth of what its light was. All photos require a certain amount of light to be exposed well. Increasing by a stop of light can help brighten an underexposed image, while decreasing an exposure by one stop will darken an overexposed image.
To increase or decrease the stops of light, therefore adjusting the exposure, we need to change the setting of our aperture, ISO, or Shutter Speed. We will go over each of these and the role they play to each other below.
Aperture
Aperture is the opening of a lens's blades, which allows light to pass through. You measure this in what is called an f/ stop, not to be confused with a stop of light. The lower the number, the wider the blades are opened and the more light that is allowed through; likewise the higher the number, the more closed the blades are and the less light is allowed through. Another key feature of aperture is the depth of field changes based on the f/ stop.
When the f/ stop is lower, it depth of field becomes less, which causes a more blurry background and creates those nice bokeh. When the f/ stop is higher, the depth of field becomes greater, which causes a much sharper background. Larger f/ stops are also useful for group photos.
ISO
ISO is best thought about as how sensitive the digital sensor of your camera is. It is not exactly that, but the easiest way to understand it is like that. The higher the ISO, the less light the sensor needs to collect.
In terms of stops of light, doubling or halving the ISO value will increase or decrease a stop of light by one. The base line for cameras ISO values tend to be 100, increasing to 200, 400, 800, etc., though most cameras have intermittent ISO values as well.
Something to keep in mind when increasing ISO is that, at high ISO values, your images start to gain a lot of color and luminance noise (the grainy pixels in photos, especially low light photos). With that in mind, many professional photographers, especially sports and wildlife, will take high noise over the motion blur caused the low shutter speed.
Shutter Speed
Shutter speed is the speed at which the shutters covering the sensor open and close. It is the measure of time that light is allowed to hit the sensor. It is measured in seconds. Shutter speed is probably the easiest of the exposure triangle sides to understand. Changing a stop of light is straight forward, double or halve the time in which the shutter stays open. For example, going from 1/100th of a second to 1/200th of a second will drop the exposure by 1 stop. Going from 1/200th. to 1/100, to 1/50th, to 1/25th will increase exposure by 3 stops of light.
Keep in mind though, the longer the shutter stays open, the easier it is to cause motion blur. Faster shutter speeds stops the light much faster and guarantees a sharper image.
Conclusion
Proper exposure is a major key to getting the perfect shot, and getting the proper exposure requires a good grip on how the exposure triangle works. With everything above, hopefully you'll be able to better understand dropping and raising in stops of light to fix your exposure where needed.
I hope you found this useful, if you have any questions, feel free to contact me to ask, follow my newsletter for more information and updates. And check out any other articles that come out.