Unit 2: Chapter 1 [Still Photography]

1.  Basic Parts of Digital Single Lens Reflex (DSLR) Camera: Lens, Sensor, Shutter, View Finder

Lens:

       The lens is one of the most important vital parts of the camera and quality of camera mainly depends on the quality of the lens.   
Or
Lens is a light-bending optical device fitted in front of a camera into the hole to focus light from subjects at various distances on to the film’s surface.

Simply Single Lenses fall into two basic categories: Concave and Convex.

ü  Concave Lenses which are thinner at the Center than at the edges bend Light rays away from the center of the Lens. 

ü  On the other hand Convex Lenses are thickest at the center and bend light toward the center of the Lens.

ü  Modern film and video camera Lenses are composed of more than one piece of glass and are called Compound Lenses.  Compound Lenses – Combine several concave and convex lenses.

A few terms used in relation to lens:

•        Optical Center: It is point on the lens through which the ray of light passed un-deviated.

•        Focus: The rays of light parallel to the principal axis passing through the lens converge to a point (in the case of convex lens) or seem to diverge from a point (in case of concave lens) on the principal axis. This point is called the focus.

•        Principal axis: It is a straight line passing through the centre of curvature of all the lens elements, and normal to all plane surfaces.

•        Focal length: The distance between the optical centre and the focus is called the focal length of the lens and usually denoted as “f”.

•        Focal plane: A plane passing through the focus of the lens perpendicularly to the principal axis is called the focal plane of the lens.

A photographic lens is composed of lenses  ( ground and polished pieces of optical glass) assembled and fitted together in a tube (usually made of metal) called a "lens barrel".   The individual lenses are known as “elements” when they are in a photographic lens.

Lens controls:

The modern camera lens has three controls: iris, focus, and Focal length/angle of view. On a fully automatic camera you may not have to adjust the focus or iris except under unusual conditions, but you should know what's going on so you can use manual settings with confidence.

IRIS: The iris is the diaphragm, and it controls the aperture. 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/1.4, f/2, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64.

FOCUS: The focus control is the ring farthest from the camera body, on the front of the lens. Distance settings are marked in meters and in feet. While a non-zoom (fixed focal length) lens is focused simply by turning the ring until the image is sharp, the zoom lens must be zoomed in to the smallest angle of view and the largest image size to adjust focus.

Angle of View

ü  Angle of View is the amount of a scene a photograph captures and can be measured vertically, horizontally or diagonally.

ü  Also known as angle of coverage or field of view, angle of view changes given the type of lens a photographer uses to take a picture.

ü  While wide-angle lens tend to capture more of a scene than any other lenses, longer lenses generally get about two degrees of a scene within their angle of view.

Focal length:

The distance between the film and the optical center of the lens when the lens is focused on infinity. The focal length of the lens on most adjustable cameras is marked in millimeters on the lens mount.

Very simply, it is the distance from the lens to the film, when focused on a subject at infinity. In other words, focal length equals image distance for a far subject. To focus on something closer than infinity, the lens is moved farther away from the film. This is why most lenses get longer when you turn the focusing ring.

Points related to  focal length of lens:

ü   Focal length controls magnification and also controls angle of view.

ü   A normal focal length lens also called standard lens, approximates the impression human vision gives.

ü   A normal lens has certain advantages over wide- angle or tele-photo lenses. Most normal lenses faster, compact, light weight and less expensive.

Types of Lenses:

	Film Format
Lens Type	35mm	6x4cm	6x6cm	6x7cm	5x4in
Ultra-wide	20mm	35mm	40mm	45mm	65mm
Wide-angle	28mm	45mm	50mm	55mm	90mm
Standard	50mm	75mm	80mm	90mm	150mm
Short-telephoto	90mm	140mm	150mm	180mm	270mm
Medium-telephoto	200mm	300mm	350mm	420mm	520mm
Long-telephoto	300mm	450mm	500mm	600mm	800mm

              

Lens Focal Length	Terminology	Typical Photography
Less than 21 mm	Extreme Wide Angle	Architecture
21-35 mm	Wide Angle	Landscape
35-70 mm	Normal	Street & Documentary
70-135 mm	Medium Telephoto	Portraiture
135-300+ m	Telephoto	Sports, Bird & Wildlife

WIDE ANGLE LENS

•        Wide Angle Lenses  are the lenses with short focal length used for landscape photography that involves capturing all the scenery in front of them. 

•        Wide angle lenses are generally used when we need wider view or when the subject is in the extreme foreground. We can use it to get more in the frame where space prevents us from stepping back.

•        Traditionally, a super wide-angle lens is classified as anything under 20mm.

•        Wide-angle is 16-35mm.

Use:

Wide-angle lenses are most commonly used for photographing landscapes and architecture, although they are often also used for photographing large groups of people.

STANDARD LENS:

•        Standard or normal lenses are used to get normal view of subject.

•        A standard lens has a focal length range of 35-70mm.

•        The most common standard lens is a fixed 50mm lens.

•        Lenses in the 50 mm to 75 mm range create natural looking portraits without facial distortions.

USES OF STANDARD LENS:

Standard lenses are most commonly used for documentary and street photography.  Pioneers of modern street photography, always used a 50mm lens, choosing to move themselves around so as to best frame an image. Good for a wide range of photographic needs but excel at portraits

MEDIUM TELEPHOTO / PORTRAIT LENS

•        The focal range between 80-135mm is nearly always used by portrait photographers.

•        Fixed lenses at these lengths produce ideal framing for head and shoulders shots.

•        It magnifies the subject.

USES OF MEDIUM TELEPHOTO / PORTRAIT LENS:

These lenses are used for portrait photography and excel in capturing good features of the subject especially human faces. These lenses are mostly used by fashion photographers to make portfolios of models. They also find use in product or commercial photography.

TELEPHOTO LENS

•        Any lens with a focal length of between 135mm and 300mm is a true telephoto lens.

•        These lenses compress the foreground and background.

•        Work well with portraits but also cause some distortion, the longer the focal length of the lens, the more it compresses the visual space.

USES OF TELEPHOTO LENS:

Telephoto lenses are traditionally used for sports and wildlife photography, but their essential function is to bring distant objects closer.

SPECIALIST  LENS

There are a variety of specialist lenses available. Some of the more common are:

•        Super Telephoto. These have a focal length of more than 300mm, and are used by dedicated sports, space and wildlife photographers.

•        Macro. These lenses are designed for extreme photography , able to focus closer to an object than normal lenses, offering a 1:1 ratio. It is used to click small object and allow  to fill the frame with small subject.  .

Fisheye. These are on the edge of wide-angle lenses (with shortest focal length), and give a distorted view of the subject matter. The center of the image is magnified, and objects diminish in size in all•        directions around it. It is also used to create dramatic effect. It captures aprox 180*(wider angle of view)