Automatic or Program modes might be fine for snapshots, but if you are at all interested in photography and taking “good” pictures, you need to know the basics.
It’s all about the light and how much light is needed to expose the image. There are several factors in determining how much light is used to create the picture.
1. Aperture or f/Stop: This is the opening in the lens that lets light in and the size of that opening is called the f/Stop. Paradoxically, a smaller number (2.8) means a large opening and a large f/number (like 22) means the smallest opening.
2. Shutter Speed: This is how long the shutter (or f/Stop) stays open. 1/30th means 1/30th of a second and is about as long as most people can hold the camera without movement showing in the picture of shaking the camera while holding it. 1/125th is a typical all around shutter speed that can freeze most movement.
3. “Film” speed: Since we are no longer using film, this number refers to the quality of the resolution. ISO is the designation, and 100 ISO is considered high quality, while 400 and 800 are starting to get iffy about the quality of the resolution. The lower numbers (100) lets in the least light (used outside in bright conditions) while the higher numbers (400 + 800) lets in the most light and is used in “low light” situations such as indoors without flash.
Those are the three factors to consider when exposing a picture. They might seem confusing or like a foreign language, but they are simply 3 factors in controlling and determining the light that creates the picture.
And ………. each of these parameters has an effect on other factors that determine how the picture is going to come out.
The f/Stop (or aperture) affects how much of the picture is going to be in focus. A large f/Stop (f/2.8) means that very little of the depth of the picture is going to be in focus. For instance, it’s possible for a nose to be in focus and the ear to be out of focus. And a small f/Stop (f/22) means that a wide area will be in focus, such as the trees in a forest where 10 feet away and 30 feet away will all be in focus.
The shutter speed (how long the f/Stop is open) might be more obvious to understand. If you take it to the extreme, then you can understand that keeping the shutter open for a long time (a minute, for instance) will show movement, such as a car passing by, whereas a quick shutter speed (1/250th) is so fast that it will freeze the motion of the car passing by and it will look as if the car is not moving.
And I’ve already mentioned the “film” speed, or ISO. Low (100 ISO) means the highest quality, but you need bright conditions in order to get a good exposure for the picture. High (800 ISO) can be used in low light situations, but often produces more grain (or digital “noise”) and might not be able to be printed to a large size.
So! ALL of these factors need to be considered when taking pictures. Yes, cameras are very intelligent these days, and Auto or Program modes are quite effective in most situations, but there may be times that you want to decide yourself which factors are more important. For instance, if you are taking pictures of a marathon, for instance, you might want a wide field of runners to be in focus and you also might not want them to be blurred with motion.