Exposure triangle is the term used for the three fundamental elements of exposure: aperture, shutter speed and ISO. Lets take a look at what each means and how manipulating each of these can have drastic effects on your images.
Aperture
The size of the opening within the lens. The wider the aperture the more light the lens allows through the sensor. Wide apertures have low f. numbers. As the aperture gets narrower the f. Number increases, the shutter speed decreases and the depth of field increases.
The confusing part?
The size of the aperture is measured in f-stops, and confusingly a lower number f-stop actually means a wider aperture. So an aperture set at f/1.8 is a lot wider than one set at f/16, letting more light in and allowing a faster shutter speed or a lower ISO.
How to use Aperture?
Aperture is used to control the depth of field. A wide aperture or a small f-stop number produces a background that is blurred whilst your subject is in sharp focus.
This is often used in portraits to ensure the focus is on the subject and not on the busy background. Conversely a narrow aperture and a large f stop number produces an image with a large depth of field.
These narrow apertures are often used for landscape photography when you want all the scene in sharp focus.
Shutter Speed
It is a measurement of how long the shutter remains open as the picture is taken. This sounds very basic but if you understand it properly can be one of the best features for artistic inspired images.
Whilst you may like to think you’re hand is super steady- its isn’t. Don’t believe me? Well, try holding your camera whilst you take a ten second exposure of some water without getting unwanted motion blur [ Hint- you can’t]. By leaving the shutter open for too long our hands move the camera during the exposure, introducing unwanted blur to the final image.
How to Stop Unwanted Blur?
The best way to counteract this is to use a tripod to keep the camera steady during your exposure. If you are planning a long exposure upwards of 30 seconds a remote trigger would be an ideal piece of kit. This will allow you to effectively press the shutter remotely [away from the camera] to start and end your exposure. This ensures the camera is the steadiest it can be and won’t shake when you press the shutter.
Best Shutter Speed for Handheld?
If you’re wondering what’s an acceptable shutter speed when using your camera handheld consider this. The 1/focal length rule determines your minimum shutter speed. The focal length in basic terms refers to the level of zoom your using and differs from lens to lens. A longer focal length requires faster shutter speeds. For example if you’re using a standard 50mm kit lens you would divide 1 by the focal length of 50 meaning you minimum acceptable shutter speed would be 1/50 second.
Minimum Shutter Speed - 1/Focal Length
How to use Shutter Speed?
Fast shutter speeds are commonly used in the following situations:
You want to capture a moving subject but want to freeze the action.
You will need to use a fast shutter speed upwards of 1/2000 if you want to capture flying birds.
You will need to use a fast shutter speed upwards of 1/1000 for fast moving vehicles.
You will need to use a fast shutter speed upwards of 1/500 for fast moving people.
You will need to use a shutter speed of roughly 1/250 for portrait photography.
Slow shutter speeds are commonly used in the following situations:
You want to capture a moving subject but want to convey the feeling of movement.
You will need to use a shutter speed of around 1/30 or slightly less for panning photography.
You will need to use a shutter speed of over 1 second for great nighttime snaps.
You will need to use bulb mode for exposures over 30 seconds. This is great if you want to get really smooth silky water, or to convey fast moving skies.
ISO
Simply referred to as the sensitivity of your camera to light.
How does ISO effect your image?
As the ISO increases, the presence of digital noise also increases. Digital noise looks like grain, and is often used in black and white photography for artistic effect. If you want grain, boost the ISO. If you want a clear image, use the lowest ISO possible.
How to Achieve the Correct Exposure:
Whilst you could use your camera's auto-exposure, if you want more creative freedom you will want to learn how to use manual mode or assisted manual modes such as shutter and aperture priority.
Exposure is all about balance. If you increase the shutter speed by a stop you will have to decrease the aperture or ISO by a stop to compensate.
If you took an image with both sets of these exposures you would have images that had exactly the same brightness but asethitically would look slightly different.
Conclusion
Learn these key things and you've got the basics needed to excel in photography. If you didn't understand anything within this post feel free to contact me and also take a look at my previous post where I outline all the terminology needed for a beginner photographer.