2. Camera Control and Adjustment:
a. Exposure- Aperture, Shutter, ISO
b. Depth of Focus and Depth of Field
c. Measurement of light -Exposure Metering System
d. Composition and Perspective
Camera Control and Adjustment:
- Exposure- Aperture, Shutter, ISO
- Depth of Focus and Depth of Field
- Measurement of light- Exposure Metering system
- Compositions and Perspective
a) Exposure- Aperture, Shutter, ISO :
Aperture?
A mechanical device that adjusts the size of the hole or a diaphragm so more or less light can pass through it.
The iris/aperture is the diaphragm, and the opening in the iris of the eye (the pupil) is the aperture.
or
The aperture of a lens is the diameter of the lens opening and is usually controlled by an iris. The larger the diameter of the aperture, the more light reaches the film / image sensor.
In optics, a diaphragm is a thin solid structure with an opening (aperture) at its centre. The role of the diaphragm is to stop the passage of light, except for the light passing through the aperture.
The aperture (the size of the lens opening) controls the brightness of the light that reaches the film. The size of the aperture is indicated by its f-number or f-stop. Bigger the number of f-stop smaller the size of the aperture. the standard series of numbers on the f-stop scale as follows:
• f/1, f/1.4, f/2, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64.
Shutter?
A light-blocking gate that can be opened to let light reach the film for a predetermined and very precise time and then shut to keep light away from the film.
An automatic mechanical device, which allows and controls the light passing through the lens and acts on the sensitive emulsion (film) or A mechanism that opens and close to admit light into a camera for a measured length of time. so as to proper exposure is known as “shutter”.
Types: Shutters are normally between-the-lens (Leaf) or Focal Plane.
- Leaf types can usually be found in older cameras, film compacts and medium format camera lenses.
- Focal plane shutters are generally used on SLR’s. Focal plane shutter – vertically running, this gives more opportunity for higher speeds as there is less travel for the blades.
The main differences between the two is the range of speeds and the highest flash (sync) speed.
Leaf shutters can sync over their complete range of 1/500sec to 4 or 8 sec.
Focal planes can run from 30sec to 1/8000sec but have relatively low sync speeds typically 1/90sec to 1/250sec.
Ø The Shutter Speed controls the amount of light by the length of time it remains opens.
Ø The faster the shutter speed, the more likely a moving subject will be sharp.
Ø Shutter and subject speed also affect the amount of blurring in a photograph.
Relation of Shutter speed and aperture:
Shutter speed and Aperture are the two controls a camera uses to make an exposure on the film when we “take a picture”.
Ø Both the shutter speed and aperture affect the amount of light entering the camera.
Ø Shutter speed and aperture also affect sharpness.
Things consider to choosing a shutter speed:
Ø Subject need to be extremely still/steady in order to not show motion / blur in the image with the shutter speed of 1/30 of a second or slower.
Ø Fast moving subjects tend to need shutter speed of 1/250 of a second or faster into order to freeze motion or prohibit blur.
Ø The faster the subject needed faster shutter speed.
Ø Low level of light limit one to a slow shutter speed.
Things consider to choosing a aperture:
Ø Choosing an aperture can dictate the amount of distance in front and behind
Ø your subject that is in acceptable focus.
Ø The larger the aperture number, the smaller the aperture hole, and the better the depth of field.
Ø The smaller the aperture number, the larger the aperture hole the less depth of field.
Ø Wide angle lenses,35mm-15mm have more depth of field per aperture.
Ø Tele photo lenses,80mm-200mm have less depth of field per aperture.
Ø Low level of light may require a large aperture hole.
ISO:
Ø In traditional (film) photography ISO* (or ASA**) was the indication of how sensitive a film was to light. It was measured in numbers (you’ve probably seen them on films – 100, 200, 400, 800 etc). The lower the number the lower the sensitivity of the film and the finer the grain in the shots you’re taking.
Ø *ISO International Organization of Standardization
Ø **ASA American Standards Association
Ø In Digital Photography ISO measures the sensitivity of the image sensor. The same principles apply as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain.
Higher ISO settings are generally used in darker situations to get faster shutter speeds.
• If your subject is moving and you’re trying freeze the motion for a still, you’ll likely need a higher ISO setting to compensate for the high shutter speed and ensure your image gets enough light.
• If you’re using a tripod to stabilize your camera you can usually get away with a slower shutter speed, which in turn allows you to use a lower ISO
• If you’re shooting an image that doesn’t require a large depth-of-field, you can increase the camera’s aperture (thus allowing more light into the lens) and use a lower ISO
• If you’re shooting with artificial light (i.e., using a flash) you can typically get away with a lower ISO setting.
b. Depth-of-Field and Depth of Focus:
Depth-of-Field: When a lens focuses on a subject at a distance, all subjects at that distance are sharply focused. Subjects that are not at the same distance are out of focus and theoretically are not sharp.
Ø Depth of field is an area, from near to far in the scene that is having acceptable sharpness in a photograph.
Ø Depth of field is an area, from near to far in the scene that is having acceptable sharpness in a photograph.
Ø Smaller the aperture size, the more that a scene will be sharp from near to far. As the aperture is stopped down and gets smaller, more of the background and foreground in a given scene becomes sharp.
Three factors can affect the depth of field
- focal length of the lens
- distance from the camera to the subject
- the size of the aperture or the setting of the f-stop
1. Focal length of the lens
The depth of field is inversely proportional to the focal length of the lens; that is, the smaller the focal length number of the lens, the greater the depth of field. For example, a 28mm lens has the ability to capture more of the picture in sharp focus than a 100mm lens.
- Distance from the camera to the subject
Depth of field is directly proportional to distance; i.e. a subject at a greater distance will have greater depth of field than a close-up subject. Therefore, you need not worry as much about a distant subject being out of focus.
- The size of the aperture or (f-stop)
A wider aperture (smaller f-stop number) will result in a shallower depth of field. You can use this to keep either the foreground or background out of focus while maintaining the subject in focus.
In the first photograph, focus on first subject with half pressed shutter release button and without releasing that, you bring second subject in an appropriate frame and then click shutter release button. Same procedure can be repeated in second picture, with second object focused. This is known as lock focus.
C. Measurement of light- Exposure Metering system:
Exposure & Exposure meter—a mechanism to regulate the appropriate intake of light coming through the combination of shutter speed and aperture. It is also synchronized with film speed.
Proper exposure is essential to taking good pictures, and is determined by accurate measurement of the light falling on or reflected by the subject, using a light meter, also known as an exposure meter.
To record the correct amount of light, camera has three exposure controls to control the amount of light.
A. Aperture (controls the amount of light)
B. Shutter speed (controls time duration)
C. ISO (controls brightness)
Exposure Triangle:
In this way, we can say that- “total amount of light allowed to reach the light sensitive material during the formation of the image.
A good combination among aperture, shutter speed and ISO are needed to produce for good exposure
A good combination among aperture, shutter speed and ISO are needed to produce for good exposure
Under exposure- when amount of light is less than required, produce under exposed image.
Over exposure- when amount of light is more than required, we get over-exposed image.
Over exposure- when amount of light is more than required, we get over-exposed image.
D- Compositions and Perspective:
The term “composition” applies not only to visual arts, but to music, dance, literature and virtually any other kind of art.
In a photography composition is simply the selection and arrangement of subjects within the picture area.
Simply put, composing an image means arranging elements within it in a way that suits the core idea or goal of your work best. Arranging elements can be done by actually moving the objects or subjects.
The main objective behind the compositions in photograph is placing figures or objects in certain positions makes some arrangements and choosing a point of view makes others.
Main points for good Composition:
ü The Rule of Thirds
ü Simplicity
ü Lines
ü Balance
ü Framing
· You can simplify your pictures and strengthen your center of interest by selecting uncomplicated backgrounds, avoiding unrelated subjects, and moving in close. If you want to make your center of interest even more dynamic, place it slightly off center in your frame.
· Generally, pictures with subjects directly in the center tend to be more static and less interesting than pictures with off-center subject placement.
· Horizontal lines communicate rest. They are the horizon of a quite meadow or water etc.
· Diagonal lines means action. They are the athlete straining forward for an extra measure of speed or the train leaning against a curved section of track.
· A feeling of depth can be best achieved by having familiar and recognizable objects at varying distances from the camera. Proper placement of objects stimulates three dimensional effect.
· Straightforward arrangements attract the eye because they express their content quickly. In picture of people or things, simplicity is a true virtue.
· Picture should almost always be made from as close as possible without eliminating any part of the subject that’s important to the snapshot or any part of the background that contributes to the meaning or the mood of it.
· When same kind of object, repeated over and over again, trails off into the distance, it also contributes a remarkable illusion of depth.
· Recognizable and familiar objects at different distances from the camera establishes a strong feeling of depth and creates three dimensional effect.
· Backgrounds are very much important in a picture. A detail filled, distracting, “busy” background will make any picture look sloppy.
· To avoid this, shift your snapping position to acquire a plain, simple, less distracting one. Sometimes, you may shoot slightly upward or downward so that the sky, horizon, trees, grass, water, beach etc. become the background.
Rule of third:
• Before you snap the picture, imagine your picture area divided into thirds both horizontally and vertically. The intersections of these imaginary lines suggest four options for placing the center of interest for good composition. The option you select depends upon the subject and how you would like that subject to be presented.
Simplicity:
• Be sure that only the things you want the viewer to see appear in the picture. If there are numerous objects cluttering up the background, your message will be lost. If you can’t find an angle or framing to isolate your subject, consider using depth of field control to keep the background out of focus.
Contrast:
• A light subject will have more impact if placed against a dark background and vice versa. Contrasting colors may be used for emphasis, but can become distracting if not considered carefully
Balance:
• Generally, informal balance is considered more pleasing in a photograph than symmetric (formal) balance. In other words, placing the main subject off-center and balancing the "weight" with other objects (smaller or lower impact) will be more effective than placing the subject in the center.
Framing:
• A "frame" in a photograph is something in the foreground that leads you into the picture or gives you a sense of where the viewer is. For example, a branch and some leaves framing a shot of rolling hills and a valley, or the edge of an imposing rock face leading into a shot of a canyon. Framing can usually improve a picture. The "frame" doesn’t need to be sharply focused. In fact if it is too sharply detailed, it could be a distraction
Viewpoint:
• You can often change a picture dramatically by moving the camera up or down or, stepping to one side. One of the best ways to come up with a prize-winning photograph is to find an "unusual" point of view.
• Direction of movement : When the subject is capable of movement, such as an animal or person, it is best to leave space in front of the subject so it appears to be moving into, rather than out of, the photograph.
Diagonals:
· Linear elements such as roads, waterways, and fences placed diagonally are generally perceived as more dynamic than horizontals.
Remember that these are only guidelines, not hard and fast "rules." While a novice can achieve quality output quickly with these guidelines, experienced photographers who know the rules often find very creative ways to break them, with excellent results.
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