lower the “f/number.” So, an f/1.4 lens is larger than an f/2.8 lens. The larger the lens, the more light it can let in to the camera. We call this a lens’ speed. So, an f/1.4 lens is “faster” than an f/2.8 lens. The larger the f/number, the smaller the lens opening or “aperture” is. So, if the light is very bright, as on a beach or snow, you would need to “stop down” the lens to f/16 or maybe even f/22, to reduce the amount of light reaching the sensor. Conversely, if the light is very dim, you would need to open up the lens to f/2.8 so that the lens can let as much light in as possible.
Here is an illustration of lens apertures:
These are the main tools you can use to control the amount of light that hits the sensor. There are also other ways of altering the light that hits the sensor. Most digital cameras today have various modes from which to choose that change the quality of light after it hits the sensor. It can be sharper or fuzzier. It can be bluer or redder. It can have a hue (color tint) to it. There are probably another two dozen ways that your digital camera can record a scene. Instead of learning about them, most people just put their camera on "AUTO" and snap away. This won't allow you to make really powerful images but it will take care of most normal scenes. So, I will write about some of the other settings in a future article. For now, if you use any of the AUTOMATIC settings (P, AUTO, Av or Tv), you will not understand your camera enough to make truly arresting images. So, one approach to understanding your camera's various settings is to set up a "scientific" experiment. Take your camera off its AUTO setting and switch to M(anual).
Then, set out to vary one group of settings at a time. To see what the APERTURE does, set your camera to ISO100 and shutter speed 1/100th of a second. Then make one exposure at each of the f/stops (apertures) your lens has as indicated in your camera's viewfinder. You should end up with a series of images from light to dark
(if you started at f/2.8 say).
Then, do the same thing keeping the aperture constant at f/2.8 and vary the shutter speeds (from 1 sec. to 1/1000th of a second). This will show you what the effect of shutter speeds have on images. Finally, do the same with ISO values. Set your lens at f/2.8 and your shutter speed at 1/100th of a second and change ISO values. You will then learn what the effect of changing them does to your images. Put the images up on your computer's screen side by side or print them to get a really good "feel" for how your camera's basic settings alter the images you make. You are then well on your way to truly understanding your camera.