Shutter speed is the most basic of elements. It is literally the speed of your camera’s shutter. The shutter is the mechanism placed between the camera’s sensor and the lens. When the shutter opens, light travels through the lens onto the sensor, creating the image. The amount of time the shutter stays open is denoted as the “Shutter Speed”. Fast shutter speeds are used to freeze time, most useful in sports or fast moving subjects. Slow shutter speeds are used to show motion, light streaks for example, or to allow the sensor to gather more light from dim subjects, such as night sky photography.
The Aperture of the lens will determine the amount of light that the lens is able to gather. This in important because the more light a lens can receive, the less time it takes to get a properly exposed photograph. Aperture values are expressed in F-stops represented as follows: f2.8, f3.5, etc. Lenses will always be labeled with their lowest F-stop. Aperture can be raised with most all lenses. This is done by “closing down” the lens, that is, rotating a number of circularly placed blades within the lens in such a way that they constrict on the circle of light that enters the lens. This will accomplish two things: increase the amount of light the sensor needs to properly expose (in turn requiring a longer shutter speed), and also increase the depth-of-field.
DOF is the term used to denote the amount of scene that is in focus. This is important for so many reasons. The most important is because what is in focus in an image is what draws the viewers attention in most cases. If a small DOF is used and the photographer does not have the intended target in focus, this can lead to a missed shot. Additionally, DOF is used at the photographers discretion to add artistic expression to an image. An image where everything is in focus will allow the viewer’s eyes to observe everything in an image whereas an image where only the subject is in focus will create a sea of what is called “Bokeh” around the subject. Most often, this manipulation of DOF is used to create landscape shots with everything in focus and portrait shots with only the subject in focus.
ISO can be described as the camera’s sensitivity to light. The lower the ISO, the more light is needed from the environment to get a properly exposed image. ISO can be adjusted on modern camera’s to compensate for lack of light. This is most commonly used to retain higher shutter speeds when shooting indoors of at night to avoid blurry images. ISO 100 is generally the starting ISO for most cameras. Each time the ISO is raised, ex. ISO 100 → ISO 200, the sensor will double it’s sensitivity to light, therefore also doubling the shutter speed (using faster shutter speeds, ex. ISO 100 with 1/50 = ISO 200 with 1/100 ) required to take the same picture at ISO 100.
That being said, each time the ISO is raised, it will introduce additional noise (grain) to your image. The introduced noise varies with each camera, and generally will be close to unnoticeable up to ISO 1600. Venturing past ISO 1600 can be risky, as the levels of noise in the image can begin to make up a large, and noticeable, part of the image.
Disclaimer: All focal lengths will be expressed in 35mm terms. That is, if you have anything less than a full-frame camera, you will have to factor in your sensor’s crop factor to determine it’s 35mm equivalence.
24mm (full-frame) → APS-C (x1.5) = 36mm equivalent Field of View (FOV)
35mm → APC-C = 52.5mm FOV
9mm → m43 (x2) = 18mm FOV
Focal length is essentially the distance from the optical center of a lens to the focusing plane in the camera, the sensor/film. The most important part of focal length is that it tells us what the lens angle of view will be. The angle of view is essentially how wide an image the lens can capture. Types of lens include the following:
Prime = Only one focal length. ex. 35mm
Zoom = Can range (zoom) from multiple focal lengths. ex. 24-70mm (can be any focal length between 24mm and 70mm.)
Specialty lens can be divided into the following categories: