THE APERTURE

is referred to the lens diaphragm opening inside a photographic lens. The size of the diaphragm opening in a camera lens regulates amount of light passes through onto the film inside the camera the moment when the shutter is pressed in camera opens during an exposure process. The size of an aperture in a lens can either be a fixed or the most popular form in an adjustable type (like an SLR camera). Aperture size is usually calibrated in f-numbers or f-stops. i.e. those little numbers engraved on the lens barrel like f22 (f/22),16 (f/16), f/11, f/8.0, f/5.6, f/4.0, f/2.8, f/2.0, f/1.8 etc. Each of this value represents one time the amount of light either more or less in quantity. Meaning to say, f/16 will let in 1X the amount of light than a diaphragm opening of f/22 and so forth; while on the other hand, an aperture of f/4.0 will let in 1X lesser than that of f/2.8 etc.

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(i) As controller of light

• Also known as the f-nos, changing the size of the aperture the lens opening through which the light enters the camera can change the exposure the amount of light that reaches the film.

• Whereas the shutter speeds controls the length of time light strikes the film the f-no controls the brightness of the light.

• It works like the pupil of an eye i.e. it can be enlarged or contracted to admit more light or less.

• In a camera, this is done with a diaphragm which is a thin overlapping metal leaves located inside the lens. The leaves are movable – meaning they can be swung out of the way so that most of the light reaches the surface of the lens passes through.

• They can be closed so that the aperture becomes very small and allows little light to pass.

• The aperture size is indicated by f-nos or f-stop. The standardized series of numbers commonly used on the f-stop scale runs as follows: f/1.4, f/2, f/2.8, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64. The largest id f/1.4 which admits the most light while the smallest f/64 admits the most little light. Each f-stop after that admits half the light of the previous one.

• The term stop is used to refer to a change in exposure, whether the aperture or shutter speed is changed. To give one step more exposure means to double the amount of light reaching the film (either by opening up to the next larger aperture setting or doubling the exposure time). To give one stop less exposure means to cut the light reaching the film in half (stopping down to the next smaller aperture setting or halving the exposure time).

DEPTH OF FIELD

The area in sharp focus

Aperture is a circle, lens form is a circle, and therefore finally the image is made by circles of confusion formed by lens refraction.

Glass elements refract (bend) light and direct them point by point to the film, resulting to mosaic of circles that form the image.

These deeds of light (circles of confusion) formed by lens refraction (area covered by the circle of confusion)

If the area is big and the circles small, the depth of field is great.

If the area is small and the circles are big, the depth of field is small (shallow).

DEPTH OF FIELD

|maximum |minimum |
|the small circles of confusion |big circles of confusion |
|big permissible circles of confusion |small permissible circles of confusion |
|small aperture opening |large aperture opening |
|shorter focal length |long focal length |

DEPTH OF FOCUS

|Depth of field |Depth of focus |
|making light from different subject distances all come to focus above |Refers to how much you can change the lens to image distance without |
|lens setting |the focused image of any one subjects growing noticeably and sharp. |

Factors Affecting Depth Of Focus

These are the same as depth of field by depth of focus increases by big aperture and large permissible circle of confusion unlike the depth of field, depth of focus increases with closer subjects distance and focal length.

DEPTH OF FOCUS

|Maximum |minimum |
|small aperture opening |large aperture opening |
|large permissible circle of confusion |small permissible circle of confusion |
|more longer focal length |shorter focal length |
|short subject camera distance |long camera subject distance |

(ii) Aperture as a controller of depth of field

The depth of field refers to the area from near to far a scene that is acceptably sharp in a photograph.

A change in aperture size affects the sharpness of the image as well as the amount of light entering the camera.

This implies that as the aperture is stopped down and gets smaller, more of the background and foreground in a given scene becomes sharp. Conversely, the area of acceptable sharpness in a picture is known as depth of field.

Examining the depth of field is a somewhat more difficult with a twin lens camera or a camera with a simple viewfinder window.

Using the shutter and aperture together
Both the shutter speed and aperture affect the amount of light that enters the camera. To get a correctly exposed negative (one that is neither too dark nor too light) you have to find a combination of shutter speed and aperture setting that will let in the right amount of light for a particular scene and film.

Both controls determine sharpness differently, i.e. the shutter affects the sharpness of moving objects while the aperture determines the depth of field – sharpness of a picture from far or near.

Note:- The smaller the aperture the less the light that enters the film and the more the depth of field and vice versa. Likewise the slower the shutter speed, more light reaches the film and high chances of motion blur and vice versa.

Film advancing lever

It is used to advance or move the exposed film frame to allow the next frame for exposure.

When the lever is not advanced especially in SLR camera, it cocks the shutter release button.

Film rewinding lever

Used to rewind or return back the exposed film into the film cassette or cartilage before it is removed for processing.

Always press inside the film rewind button (usually in the base of the camera) before you turn the rewind crank clockwise until the film is released from the takeaway spool.

However, other cameras have an automatic rewind mechanism. For digital cameras, the frames turn on automatically since the cameras use memory cards.

Hot shoe

Used for synchronized flush shot mechanism

The hot shoe is usually found in professional cameras with removable flash.

It is used to hold portable flash units/external flash.

Self-timer

The self-timer is an automatic mechanism which can be set to delay for a few seconds in cases where the photographer wants to be part of the rest in the photograph.

The lens

Used to collect light rays coming from a scene in front of the camera and project them as images onto a piece of film at the back.

Lenses can be classified as telephoto, wide angle lens, zoom lens, normal focal length lens, macro lens, etc.

Types of lenses

a) Standard lens

Standard lenses are also called normal lenses. They are provided by the camera manufacturers along with the camera as a part of the kit. There are generally of the 18.55mm focal length for a normal 35mm camera. b) Wide angle lens

These are lenses which have focal length than the standard lenses, which helps in getting more area of view in the frame from the same distance. Typically used for landscape photography. These lenses can increase the perspective distortion, so caution is recommended c) Telephone lens

These are lenses with Focal longer than the standard lens. They are also called, especially for nature and wildlife photography where you can not go near to the subject but want to fill the frame with the subject from a distance. Normally 70-300mm lens is recommended for such purposes though different combination can be based on your requirement. d) Zoom lenses

These are lenses with variable Focal lengths. In these lenses, the positive and negative elements o the lens are put together in such a way that by moving them you can get varied focal lengths. You can also find telephone lens with zoom lens capabilities. e) Micro lens

These are lenses designed to do close up photography like flowers, insects. Basically the macro lenses have very high focusing movement than the normal lenses.
Advantages and Disadvantages of type of lenses

a) Advantages of zoom lenses

i) Zoom lenses are convenient since they allow a photographer to vary Focal length. Therefore no delays missed pictures as may be the case when having to change from one lens to another

ii) Zoom lenses are versatile and can be used creatively by changing their Focal lengths while the shutter is open. One result is to give a feeling of motion to a stationary subject and another is that it can produce abstract images or interesting patterns

iii) Photographers create interesting photographic effects, including one of motion by zooming the lens in or out during the actual exposure.

iv) Photographers making colour slides for projection especially like zoom lenses because they can easily fill the frame with exactly the picture they want to show on the screen

Disadvantages of zoom lenses

i) Many zoom lenses are heavy and bulky compared to those of fixed focal lengths

ii) Comparing the minimum focal length of zoom lens to a regular lens of that same focal length, the zoom lens usually will have a smaller maximum f/stop opening. This means that in situations where the light level is low, same zoom lenses are less useful than lenses of fixed focal focal lengths.

iii) Zoom lenses do not maintain their sharnes as you change the focal lengths. Thus after zooming in or out to frame your subject, you may have to refocus in order to get the sharpness possible image.

b) Advantages of Telephoto lenses

i) The most popular, 90mm, 105mm and 135mm enable portraits to be made without distortion of the subject features and without getting uncomfortably close.

ii) They put you where the action is, especially at sports events where fans and photographers are required to keep their distance

iii) Nature photographers count on telephoto lenses to get near subjects without disturbing them, a necessity for bird and wildlife pictures.

iv) Travel photographers use telephotos to capture informal portraits of people without their being aware of the camera.

v) Filling your frame with subject is a basic rule for making effective pictures and telephoto lenses allow this quite easily.

Disadvantages of Telephoto lenses

i) They work for sports, nature or wildlife photography because they allow you to get much closer to your subject. If you will not be shooting those kinds of subjects however, the features that make a telephoto lens might actually inhibit your ability to take a good pictures.

ii) Because they have such long focal lengths lower than with a standard or a wide angle lens. This means that only the subject will appear in focus while most of the foreground will be blurry. This low depth of field can make the subject appear isolated in the image and can also compress the space between the foreground and background, making the image look two dimensional.

iii) They have much of a scene or subject you can include in your picture. If shooting landscape, cityscapes or interiors, this could be frustrating Telephoto lenses are more cumbersome than standard or wide-angle lenses and carrying them can be difficult while traveling or attending crowded events. Super telephoto lenses can weigh 10-12 lbs (5-6 kg).

iv) Telephoto lenses are often more expensive than standard lenses.

c) Advantages of standard lenses

I) They suit the requirements of most photographic situations. It is ideal for the subjects that interest the majority of photographers

II) They are usually faster than lenses of other focal lengths, allowing for easier framing and focusing, higher shutter speeds to stop more action and full exposure under dimmer lighting conditions.

III) It is generally sharper and better corrected than telephoto wide-angle lenses and zoom lenses although the difference is quite small.

IV) Even with its extra speed and clarity, a standard lens is smaller and lighter than any telephoto or zoom lens and most wide angle lenses.

V) For complex optical reasons normal lens are able to focus much closer than those of longer focal lengths. Although wide angle often have this ability too, their enormous depths of field makes precise focusing more difficult than with normal or standard lenses.

VI) The coverage of the average flash has been matched to the field of view of the standard lens. In the typical indoor situation in which flash is used, a tepephoto lens is impractical, a wide angle lens takes in more than flash covers (resulting in light fall off in picture corners) but a normal lens is ideal.

Advantages of macrolenses

Enable a photographer to photograph small subjects in great detail capturing up to life size reproductions (image appears same size on the film plane)

i) Macrolenses are typically very sharp, which help in capturing fine detail of small subjects

ii) They allow necessary precise manual focusing

iii) Have narrow field of view and a greater working distance from your subject which helps create fantastic images.

Disadvantages of macro lenses

i) The longer focal length of macro lenses cost significantly more money and are heavier

ii) Their depth of field is so shallow that it rarely focuses where you want

iii) While using micro lenses, the camera is only seeing the light reflected froma small area which makes the view through the view finder dim and difficult for focusing.

Advantages of wide angle lenses

i) They can capture wider within the confines of a photo, but to do so, it has to shrink the elements of the image

ii) When you get close to your subject, it expands nearby objects and diminishes further objects. It adds a feeling of depth to your photos

iii) They make the foreground jump out for a more dramatic photo

iv) They give an enhanced feeling of depth and height

Disadvantages

i. When you are close to an object, they tend to distort and stretch the subject out of proportion, which is not desirable effect.

ii. Prone to vignetting and can often produce photos with soft edges the entire photo may be sharp except for the edges

iii. Have limited zoom. They are fantastic for taking close photos of objects but are almost unless when trying to capture objects that are far away distance.