... an article on aperture and shutter speed, ... Can someone point me in the right direction?
The most basic question in photography...
Aperture and shutter speed are two legs of the exposure triangle, with the third leg being ISO. All three must balance for proper exposure.
Aperture is the size of the iris in the lens. A large aperture (small
f-number) lets in more light.
Shutter speed is how long the exposure lasts. The longer the shutter is open, the more light falls on the sensor (or film.)
ISO is a measure of sensitivity to light. In film, it was an indication of the film's ability to react to light chemically. Higher ISO (or ASA as it used to be called) was "faster" film, meaning more sensitive, requiring less exposure for an image. ISO in a digital camera is an electronic setting for gain in the sensor's amplification of the light received. In a low-light situation you can set a higher ISO to make your camera more sensitive to light, comparable to faster film.
All three settings together produce an exposure value, the amount of light on the sensor and how much that light is amplified by the camera's electronics.
All three are incremented in "stops." One stop difference either halves or doubles the exposure. If ISO 100, 1/250th and
f:4 is a correct exposure, then you could change the shutter speed one direction by a stop, and the aperture or ISO the other direction by a stop, and still have correct exposure. So ISO 200, 1/125 and
f:4 is still correct exposure, as is ISO 100, 1/125 and
f:5.6.
Notice that doubling or halving the number for ISO and shutter doubles or halves the exposure, but the number for aperture moves differently. Aperture is a measurement of the
area of the iris, so its 1-stop change is by a factor of the square root of 2, not actually of 2.
So how do you decide what to use, if literally well over a hundred combinations of the three give correct exposure? That's where experience and judgment come in, and there's no substitute for playing with the settings and learning how they affect your image.
As a rule, you want to use the lowest ISO you can get away with, as higher ISO, meaning more amplification, adds noise to the image, seen as a "grainy" effect, where color areas that should be smooth actually have many pixels of not quite the right color or exposure. So ISO can affect the "cleanliness" of the image, especially on lower-priced cameras.
Shutter speed can affect how much motion is captured in an image. You probably want a fast shutter for action shots, where for landscapes from a tripod it almost doesn't matter. There might be a creative need to introduce motion blur, giving a still frame a sense of motion. At air shows, for example, you don't want to freeze the propeller of an airplane, making it look "parked" in the sky. You want a slow enough shutter to blur the prop, but fast enough to not blur the airplane itself. On the other hand, when shooting jets at an air show, the fastest shutter you can use is probably appropriate.
Aperture affects depth of field. Large apertures (lower
f-number) reduces depth of field, meaning the subject could be well focused but items in the image at a different distance will not be in focus. This is usually intentionally done to get a blurred background. A small aperture, on the other hand (larger
f-number,) give a high depth of field, perhaps even nearly infinite depth of field. With that, your entire landscape image is in focus and sharp. Also, depth of field in either case will be smaller if the subject is closer to the camera, so even a small aperture can blur the background if you're focused on something very close.
Cameras usually have auto-exposure modes, as well. Fully automatic, the camera decides what it thinks is appropriate. You can also shoot aperture-priority, forcing the camera to use a specific aperture, or shutter-priority, forcing the camera to use a specific shutter speed. Again, experience and judgment are you guides here as to what is appropriate to use in a given situation.
Play with the camera, see how the images change with different combinations of the settings.