Shooting Mode: Determine objective | Depth of field
Shooting Mode: Determine objective | Depth of field | ||
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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 role of the ISO setting was discussed in How to set the ISO sensitivity ratings for your digital camera. 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. Depth of field is a term that describes the area from near to far that is in focus; in other 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 sup- port 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. If the objective was to have as much of the photo as possible be in focus, the choice of f-stop was near the maximum f-stop available on the Nikon CoolPix 950, such as f/11.0. However, if there is no tripod available and not much light is in the barn where the subject is, the smallest f-stop that could be used is f/2.9. This setting is just about the worst setting that could be used to maximize the depth-of-field, but it worked! If a tripod is available, you can try to set the the camera to f/8.0. If the objective here was exactly the opposite of the previous case, it was to have as shallow a depth-of-field as possible. 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 depth-of- field, you can understand the challenges of capturing a photo as you envision it! | ||