Determine What You Want The Photo to Look Like
Before you can choose an appropriate exposure mode, you must first determine what you want the photo to look like! It sounds simple, but visualizing how a photo should look before you take it is a skill that must be acquired. Those who have it take better photos than those who don’t have it. If you don’t have it yet, don’t worry; keep reading and keep shooting.
All cameras (whether they are digital or film) expose either an image sensor or film with light. Light entering the camera is controlled in three important ways: the amount of time the shutter is open, the size of the lens opening, and the ISO setting. The larger the lens opening, the faster the light exposes the image sensor or film. The corollary is the smaller the lens opening, the longer the shutter will have to be open in order to allow the same amount of light in to expose the sensor or film.
The size of the lens opening (or aperture) is referred to as the f-stop. Most compact-level digital cameras have f-stops ranging between f/2.0 and f/11.0. Understanding f-stops can be a bit confusing because the number is actually the denominator of a fraction with 1 as the numerator. In other words, f/2.0 is really 1/2.0 (or 1/2) and f/8.0 is really 1/8.0 (or 1/8). These fractions represent the opening size; so, f/2.0 is a larger opening than f/8.0.
When thinking about this concept, you may wonder why photographers care so much about which combination of f-stop and shutter speed they use if different combinations result in the same level of light entering the lens.We care because a small opening results in more depth-of-field than a large opening. Depthof-field is a term that describes the area from near to far that is in focus; in ther words, it describes how much of the image is in focus.
Furthermore, because a smaller opening requires that the lens be open longer to get the same amount of light as a larger opening, an image has an increased chance of being blurred if the camera or the subject moves during exposure. In this case, a camera support would be recommended. So, the trick is to get the proper depth-of-field and the desired degree of image sharpness with the available light.
PHOTO FROG
The above is a photo of a small frog. The objective here was exactly the opposite of the photo of the old work boots—it was to have as shallow a depthof- field as possible. Notice how the right eye of the frog is clearly focused and the left eye and everything further from it is blurred. Likewise, the foreground leaves are also blurred. Given the chance to shoot this photo again, I would try to shoot with a slightly smaller f-stop (for example, f/8.0 instead of f/4.0) so that both eyes would be in focus. The problem then would have been to hold the camera still enough to avoid causing image blur due to camera movement at the resulting slower shutter speed.
You should also now understand the importance of deciding what your photo should look like before shooting. Otherwise, how will you optimally set the camera settings? You can shoot with an automatic setting, or you can choose your settings carefully for each shot you take. Often, many of photography’s trade-offs and limitations make getting the photo that you want challenging and that is why some photographers are better than others. The good ones learn to envision a shot, and choose the best settings based upon the constraints and trade-offs that face all photographers.
With that quick and possibly overly simplistic overview of f-stop and shutter speed, the discussion of the resulting effects that different combinations can have on image blur (due to subject movement or to the photographer’s inability to hold the camera still while shooting), and the nuances of epth-offield, you can understand the challenges of capturing a photo as you envision it!
