EXPOSURE
Three things, ISO, shutter speed and ƒ-stop, control exposure. Your camera has a coupled meter system to help you achieve the correct exposure. In (M)manual you will see the metering in the viewfinder and/or on the rear screen. You adjust the ƒ-stop, shutter speed and ISO manually as you see fit. A meter in a camera is still a fairly new invention. Today's cameras are computer controlled and while more confusing at first, the camera will help you create photography with fewer problems. Other exposure modes include (P)program, (A)aperture priority, (S or Tv)shutter priority, (Auto)full automatic, and (Scene).
The sensitivity of the chip or film is called ISO. Film comes in preset speeds or ISO while digital allows a wide range of sensitivity levels (ISO) that can be changed at any time by the photographer.
Well why would I need that? You can shoot on a sunny day at the beach and after dark you can turn up the sensitivity and shoot under room light. The primary reason is to balance the other two controls. All three work together to allow you to control moving subjects, depth of field, and quality of image
ISO range is generally 100 to 6400 or more. The lower number has the best quality. Noise grows in the image with higher levels. Your camera uses algorithms to surpress the noise but at high ISO the image will look grainy and or clumpy as the pixels need to bunch up to gather enough light. If you need to shoot at at fast shutter speed and need depth of field you will need to raise the ISO. You can get very acceptable results up to ISO 2000 depending on your subject, and if necessary, accept a little noise and raise the ISO higher. Noise is not always a bad thing.
Your shutter speed is used for stopping movement of yourself, and or the subject. Many images can not be enlarged because the photographer got nervous and didn't push the shutter smoothly or did not have the camera under control. A rule of thumb for holding the camera, is, if you have a normal (50mm) lens you should have a shutter speed of no less than 1/50. If your zoom lens goes to 100, then you should be shooting at no less than 1/100. A child at rest can be photographed with a slower shutter speed. An active child may require 1/250 or faster to stop the action. Sometimes we want motion in the image so we need that slower shutter speed. Shutter priority (S) is the setting you need when shutter speed is the priority.
The ƒ-stop, also called the iris or aperture, like the shutter speed, controls the amount of light coming into the camera. Your aperture is part of the lens while the shutter is in the camera. There are standard numbers ie: 2.8, 4, 5.6, 8, 11, 16, 22. The smallest number allows the most light. It is the largest aperture. As the numbers get higher the diameter of the aperture gets smaller. Well why didn't the numbers go the other way? Each number equals the number of diameters of the aperture that corresponds to the distance from the center of the lens to the sensitive plane in the camera. The aperture does not change the focus of the lens but when stopped down to a larger number you will gain apparent focus. This is called depth of field. An aperture with a small number (2.8) will have a shallow depth of field and will isolate the object focused on. When depth of field is most important use (A) Aperture priority.
Using Aperture or Shutter priority or Program are automatic settings for creating the correct exposure while allowing your creativity. Full Automatic will give you a good general exposure but defeats the creative options offered by the camera. Manual setting turns you loose to intentionally make adjustments for creative purposes. If you are photographing the Grand Canyon or even close-ups of flowers you can try (Scene) but I prefer to have control. So now its time to try out the camera and test our skills. Don't be afraid to try things and make mistakes. You learn by your mistakes and using digital is a lot cheaper than using film.
