This is all about how you arrange a photo and there are loads of different ''rules'' on how to do it. But you shoud see them more like suggestions. Rules are made to be broken, right?
The most common rule is rule of thirds. What you want to do is to make your object of focus be close to where the lines meet. If you're taking a photo of something with a face you'd like to let it look inwards.
Another common rule is the golden spiral and it's a way to guide the viewer in a well-balanced photo.
Apeture is how wide the lens is open. Apeture is measured in ''f-stop'' witch is a number.
Depth of field
DoF is the range before and beyond the subject which are also in reasonably sharp focus. One point on which you focus will be the sharpest, but that focus doesn’t disappear immediately outside of that subject.
The areas closer or farther away than the focal point will be less sharp than the subject, but will still appear to the eye to be in reasonably good focus. The broader the physical range of sharpness, the greater the depth of field.
Controlling the amount of light that enters the camera is vital to achieving a correctly exposed photograph.
First measure the amount of light available in the room or setting, and adjust the aperture and shutter speeds to allow the needed amount of light to reach the film or the camera’s sensors.
Exposure is the effect of the total amount of light reaching the film or the sensor. If not enough light reaches the film or sensor the image will be underexposed. Too much light results in an overexposed image.
The f/number is a measurement of the size of the lens opening. These numbers are standardized on lenses as follows:
1.0 1.4 2.0 2.8 4.0 5.6 8.0 11.0 16.0 22.0
When you change an f/number, you’ll either be doubling the amount of light being allowed in to the film or sensor, or cutting it in half.
Focal length is another lens feature it’s important to understand. The focal length of the lens is measured when the focus is set to infinity, and is the distance from the optical center of the lens to the film (or sensor) plane.
The focal length of the lens determines how large each object in the shot will appear on the film or the sensor. A 50mm lens is considered a normal lense when shooting with a 35mm film format camera, because the angle of view approximates the diagonal size of the film. A lens shorter than 50mm is considered a wide-angle lens, and longer is classified as a telephoto lens. There are also variable focal or “zoom” lenses which have more than one focal length.
The focal length of the lens is measured in millimeters, such as 28mm, 50mm, 105mm, etc., and is indicated either at the mouth or on the barrel of the lens.
Shutter speed describes the amount of time that the shutter is open, or in digital terms it’s how long the sensor is exposed to “see” the shot that you’re taking. It’s a measure of how long the film or sensor is exposed to light, which is the basic control for taking pictures on a camera. The exposure time is controlled by the shutter speed dial on the camera.
Shutter speed is usually measured in fractions of seconds – the faster you want the shutter speed to be, the higher the number you’ll select on the dial. For example, 1/1000 is much faster than 1/30 - which means that less light will enter the camera.