What is a DSLR
A Digital Single-Lens Reflex camera is a camera that has a mirror inside of it positioned in front of the camera’s sensor. The mirror directs the light to the viewfinder and means that what you see through the viewfinder is almost identical to what the sensor will capture.
Also on a DSLR you can change the lenses depending on what you are shooting. This opens up creative options and the ability to change focal lengths. The focal length of a lens determines its angle of view, and also how much the subject will be magnified. Wide angle lenses have short focal lengths, while telephoto lenses have longer corresponding focal lengths.
Aperture, Shutter-speed & ISO
Aperture, Shutter-speed & ISO are terms that you will hear a lot over the course they are the three elements that affect the exposure of an image. A good exposure is one that retains detail in the highlights and shadows.
Underexposed Correct Exposure Overexposed
Aperture
This is how open or closed the Iris is, the iris is a metal diaphragm consisting of several metal blades that will open or close. The wider open the iris is the more light it allows in. The iris/aperture can be opened in increments called f-stops. A wide aperture on a lens is useful for shooting in low light situations or if you want a small depth of field. The depth of field is how much of the subject is in focus.
If you are shooting portraits outdoors you might want a blurry background this requires a wide aperture like f/1.8. If you are shooting a landscape or building you will probably want the whole building to be in focus and sharp so you would need a higher f-stop number so a more narrow aperture of f/11.
Here’s an example of how the f-stop affects the sharpness and focal point of an image.
Shutter speed
In front of the sensor in a camera is something called a shutter this shutter opens and closes at fractions of a second. In doing so it allows light in and stops it once the image is captured. This is another way of controlling the exposure of the image but also affects how much motion blur is in the image.
This example here shows how a slower shutter speed and a fast moving object creates a motion blur effect. It can be used to creative effect but it won’t suit every situation.
Motion blur will affect the sharpness of your image and if you are taking photos of sports events or even your kids running around with a slow shutter speed you’ll find your images to be unusable.
If you want to capture fast moving objects you need a faster shutterspeed, for sports it needs to be 1/500th of a second or faster.
To create a motion blur effect or light trails a very slow shutter speed is needed of anything slower than 1/25th of a second.
ISO
ISO is a term that goes back to when film was the main medium of photography. The ISO is an indicator of how sensitive the film is to light. The higher the ISO the more sensitive it is. With digital camera’s we of course don’t use physical films but you can adjust the camera sensor’s sensitivity to light and this too is called an ISO setting.
For shooting in a studio with flash you would use ISO 100 or on a bright day ISO 200-400 and at night you would use anything from ISO 400 to 1200 to increase the sensors sensitivity to light. There is a consideration to make however. If your ISO is too high it will introduce digital noise to the image and this noise will affect the overall quality of the image.
An example of digital noise.
Balancing for Exposure
It is always a balance of Aperture, shutter speed and ISO to get a good exposure. You can’t change one setting without having to change the other. In Aperture priority mode and Shutter priority mode the camera will adjust the other setting to compensate but you will need to set the correct ISO for the situation first. If you are in manual you will need to adjust all the settings yourself. Below is an exposure triangle If you move one setting towards the outside of the triangle in effect you would need to bring one or both of the other settings in towards the centre.
You should always make your settings decisions based on what you want from the image. It’s important to think about what you need from it. So an example of that would be shooting a sports event, you want to capture the runner as they cross the finish line it needs to be sharp with no motion blur. We have seen that to eliminate the motion blur we need a fast shutter speed of at least 1/500th of a second but that reduces the light entering the lens and we don’t want to open the aperture too much because we want it to be sharp so we need to increase the ISO. To help make these choices you can use a light meter or an exposure calculator. A free exposure calculator can be found online at http://www.calculator.org/calculate-online/ photography/exposure.aspx there are also free exposure calculator apps for android and apple.
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