Balance

• To some degree, every photograph in existence has elements of both balance and imbalance.
• A perfectly balanced photo means that the left and right halves of the photo draw the eye equally.
• The left-right division is the only one which really matters, top-bottom balance has little effect on how evenly-weighted an image appears.
• The most obvious type of balance is symmetry,where the image is identical on the left and  right halves.
•  Another type of balance is asymmetrical balance. This happens when each half of the photo has a subject that attracts equal attraction.
• To know how to balance a photo, you need to know what attracts viewer's eyes in a photo.

1. Areas of contrast
2. Items that are in focus(especially if most of the photo is not
3. Bright spots
4. Saturated items
5. Warm(red/yellow) colours
6. Large items
7. People and (to a lesser extent) animals
8. The eyes of your subject
9. The direction that your subject is looking.(Even if it is an empty space, it gains visual weight because viewers will want to look the same direction as the subject.

Depth of Field

• also called focus range or effective focus range
• the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image.
• In some cases, it may be desirable to have the entire image sharp, and a large depth of field(deep focus) is appropriate.

 

•  Whereas in other cases, a small depth of field(shallow focus) maybe more effective, emphasizing the subject while de-emphasizing the foreground and background.

Rule of Thirds

• A guideline which applies to the process of composing visual images.
• an image should be imagined as divided into nine equal parts
• There are two equally spaced horizontal lines and two equally spaced vertical lines.
• Important compositional elements should be placed along these lines or their intersections.

A photograph that demonstrates the principle of rule of thirds

Composition

• describes placement of relative objects and elements in a work of art.
• A good composition has just enough detail.
• Too few elements robs the work of art of necessary detail that makes correct interpretation possible.
• Too many elements can be very distracting.
• Composition guides the viewer's eye towards the most important elements of your work.
• the goal of composition is to help express the idea of the artist by necessary means.  

Shutter speed

• also known as exposure time
• is the length of time when the film or digital sensor inside the camera is exposed to light.
• shutter speed in conjunction with the aperture and the scene's luminance determines the exposure value.
• multiple combinations of shutter speed and f-number can give the same exposure value.
• shutter speed changes the way movement appears in photographs.

          1) Very short shutter speeds can be used to freeze fast-moving subjects.
               Example: A bubble popping

 

          2) Very long shutter speeds are used to intentionally blur a moving object for effect.

               Example: Stars moving in the night sky

•  There is an agreed standard for shutter speeds.

Aperture

• in photography, aperture refers to the diameter of the aperture stop, a device called a diaphragm acts as the aperture stop in a camera, and controls the effective diameter of the lens opening.
• The aperture stop can be adjusted to control the amount of light reaching the film or image sensor.
• works in combination with shutter speed. Typically a fast shutter speed requires a larger aperture to ensure sufficient light exposure. Whereas a slow shutter speed will require a smaller aperture to avoid excessive exposure.
• The lens aperture is usually specified as an f-number. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. 

Exposure

•  is the amount of light per unit area reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance.   
• is measured in lux seconds, and can be computed from exposure value(EV) and scene luminance in a specified region.
• is generally referring to a single shutter cycle.
• is classified into three types : 

  1) Optimum Exposure

        Correct exposure is an exposure that achieves the effect the photographer intended. Exposure adjustment is done to control the physical amount of  light from the subject that is allowed to fall on the film, so that significant areas of shadow and highlight detail do not exceed the film's useful exposure range. This ensures that no significant information is lost during capture. 
  

  2)  Overexposure

        A photo is overexposed when it has a loss of highlight detail, that is, when important bright parts of an image are "washed out" or effectively all white, known as "blowned-out highlights" or "clipped whites". 
  

  3)  Underexposure

         A photograph may be described as underexposed when it has a loss of shadow detail, that is, when important dark areas are "muddy" or indistinguishable from black, known as "blocked-up shadows" or sometimes "crushed shadows", "crushed blacks", or "clipped blacks".
   
  

  3 photos taken at the same location displaying three different exposures.

  

  Underexposure                   Optimum exposure                Overexposure