There are three primary variables to contend with in photography. They are ISO, APERTURE, and SHUTTER SPEED. The goal is to set these based upon the light you have for the best chance of a sharp, properly exposed picture. None of these variables is independent. Change one, and it impacts the other two.
ISO – This is the same as film speed in the by-gone days of film cameras. The lower the ISO number, the less grain and finer the detail the image will present. A low ISO allows the picture to retain resolution when enlarged. But more importantly, a low ISO allows cropping the photo to get the best view of the subject or improved composition while keeping adequate image resolution. A low ISO with a large camera sensor (like FX) is wonderful because you have a lot of resolution and pixels to work with in editing. The lower the ISO, the more light that is needed for proper exposure. 64 or 100 is a low ISO, 3600+ is a high ISO.
Aperture or F-Stop – This is the opening in the lens that lets the light in. The smaller the number of the aperture, the larger the hole, so more light is allowed onto the camera sensor. Also, the smaller the aperture number has the narrower the depth of field. Depth of field is how much before and after the point of focus things will still be in focus. For example is you take a picture, focusing on your dog’s eyes, with a small aperture number (like f/1.8), then the eyes are sharp in focus, but his nose may not be. If you increase the aperture number (which makes the opening that lets in light smaller) to say f/8, then the whole head is in focus. The higher the F-stop number, the greater the depth of field, but more light is needed for proper exposure.
Shutter Speed – This is how long the shutter is open, exposing the camera sensor to the scene. The faster the shutter speed, the more action is frozen (less blur), but the light is allowed in for less time. So, a fast shutter speed needs brighter light for proper exposure.
Here is a helpful diagram depicting the interdependence of these three variables.
Another element to consider is the focal length of the lens you are using. The focal length is unique to each lens and describes the angle of view (how wide or narrow) of the scene captured and the magnification. A zoom lens lets you change the focal length within a pre-designed range. A 20mm lens is a wide-angle, and images appear farther away. A 50mm lens is about what your eye sees. A 300 mm lens narrows and magnifies the field view. A 300mm lens is about 6x magnification. The higher the focal length, the faster the shutter speed must be to capture sharp images because the magnification exaggerates camera shake. Many shots in the field require as much focal length as you have on your lens, which drives the required shutter speed up and impacts the other two variables (ISO and Aperture). Just something else to consider.
On a bright day, you can have all these variables where you want them. You can use your 200mm lens with a low ISO (64 or 100), so your pictures have little or no grain, a high aperture (say 8 and up) so you get lots of depth of field and a fast shutter speed (say 1/1,000 of a second or faster) so you freeze the action. This is the best chance for super-sharp pictures. Now all you got to do is find the great subject and compose the image well! The challenge is that the light is often not adequate, so you need to adapt by changing your camera settings.
Part 3 – Camera Settings will be published soon. I hope you found this helpful and I appreciate you visiting the Birdhunter!