CAMERA

Slide 1 : Camera

Slide 2 : CAMERA A camera is a device used to take pictures (usually photographs), either singly or in sequence, with or without sound recording, such as with video cameras. A camera that takes pictures singly is sometimes called a photo camera to distinguish it from a video camera. The name is derived from camera obscura, Latin for "dark chamber", an early mechanism for projecting images in which an entire room functioned much as the internal workings of a modern photographic camera, except there was no way at this time to record the image short of manually tracing it. Cameras may work with the visual spectrum or other portions of the electromagnetic spectrum. Every camera consists of some kind of enclosed chamber, with an opening or aperture at one end for light to enter, and a recording or viewing surface for capturing the light at the other end. Most cameras have a lens positioned in front of the camera's opening to gather the incoming light and to focus the image, or part of the image, on the recording surface. The diameter of the aperture is often controlled by a diaphragm mechanism, but some cameras have a fixed-size aperture. The size of the aperture and the brightness of the scene control the amount of light that enters the camera during a period of time, and the shutter controls the length of time that the light hits the recording surface. For example, in lower light situations, the shutter speed should be slower (longer time spent open) to allow the film to capture what little light is present.

Slide 3 : Camera Obscura (DARK ROOM) It is not known who the first people to discover the “dark room” were. The word “camera” means room in Latin and the word “obscura” means dark. A camera obscura is just that – a dark room with a hole in one side. The hole focuses the light to produce an image of what is outside. The image is produced upside down on the wall opposite the hole. Optics The first people to understand how light worked may have been the Chinese or the Greeks around the 4th or 5th centuries B.C. Chinese philosopher Mo-Ti described a camera obscura, and Aristotle understood the principles. How It Works The camera obscura is simply a room, or even a box, with a hole in one side. The hole acts like an aperture in a camera, focusing the light. The day must be bright, and the room must be dark, but the image will appear clearly on the wall opposite the hole. Because the sun’s rays travel in a straight line, they produce an image on the wall that is reversed (upside down).

Slide 4 : Step 1: Obtain Oatmeal Box. Step 2: Cut 2” x 2” hole in the side. Step 3: cover paint inside of box black. Also cover the lid, inside and out, black. Step 4: Test to make sure there are no light leaks. Step 5: Use a heavy aluminum foil or tin from a pie plate to make the pin-hole. Cut a square that is slightly larger than the hole in your oatmeal box. Step 6: Use a pin to make a hole in the center. Carefully smooth out the edges of the pin-hole by pressing the aluminum against a desk or table until it is flat. Step 7: Use black permanent magic marker to color the pie tin square. Step 8: Be sure not to “cloud” the pin-hole with ink. Step 9: Use black electrical tape to tape the pie tin to the inside of the oatmeal box. Be sure that the tin completely covers the hole and that there are no light leaks! Step 10: Use heavy black paper to create a cover for the pin-hole. Tape it to the side of the pin-hole and use rubber bands to secure it. Step 11: Now you’re ready to load your camera! Step 12: In a darkroom, under red light, put a fresh sheet of photographic paper, shiny side toward the pin-hole, on the opposite wall from the pin-hole. If necessary, tape it in place. Put the lid back on your camera before going out of the darkroom.

Slide 5 : PATH OF LIGHT

Slide 6 :

Slide 7 : ELEMENTS OF CAMERA The photographic camera thus involved is light-tight chamber / box with a lens at one end and film or plate holder at other end with focusing system, diaphragm, shutter, view - finder etc. VIEW FINDER:- The viewfinder is the "window" or frame on a camera showing the scene that will appear in the picture. Or The viewfinder shows you the entire scene that will be recoded on the film / memory and indicates which part of the scene is focused most sharply.

Slide 8 : 2- LCD on a Digital Compact Camera (TTL):- The LCD on a digital compact camera shows in real time what is projected onto the sensor by the lens and therefore avoids the above parallax errors. This is also called "TTL" or "Through-The-Lens" viewing. Using the LCD for framing will shorten battery life and it may be difficult to frame accurately in very bright sunlight conditions, in which case you will have to resort to the optical or electronic viewfinder . The LCDs on virtually all digital SLRs will only show the image after it is taken and give no live previews. TYPES OF VIEW FINDER:- 1- Optical Viewfinder on a Digital Compact Camera:- The optical viewfinder on a digital compact camera consists of a simple optical system that zooms at the same time as the main lens and has an optical path that runs parallel to the camera's main lens. These viewfinders are small and their biggest problem is framing inaccuracy. Since the viewfinder is positioned above the actual lens (often there is also a horizontal offset), what you see through the optical viewfinder is different from what the lens projects onto the sensor. This "parallax error" is most obvious at relatively small subject distances.

Slide 9 : 3- Optical Viewfinder on a Digital SLR Camera (TTL):- The optical viewfinder of a digital SLR shows what the lens will project on the sensor via a mirror and a prism and has therefore no parallax error. When you depress the shutter button, the mirror flips up so the lens can expose the sensor. As a consequence, and due to sensor limitations, the LCD on most digital SLRs will only show the image after it is taken and give no live previews. In some models this is resolved by replacing the mirror by a prism (at the expense of incoming light). The optical viewfinder normally also features an LCD "status bar" along the bottom of the viewfinder relaying exposure and camera setting information. 4- Electronic Viewfinder (EVF) on a Digital Compact Camera (TTL):- An electronic viewfinder (EVF) functions like the LCD on a digital compact camera and shows in real time what is projected onto the sensor by the lens. It is basically a small LCD (typically measuring 0.5" diagonally and 235,000 pixels) with a lens in front of it, which allows you to frame more accurately, especially in bright sunlight. It simulates in an electronic way the effect of the (superior) optical TTL viewfinders found on digital SLRs and doesn't suffer from parallax errors. Cameras with an EVF have an LCD as well, but no true optical viewfinder.

Slide 10 : LENS:- The lens is one of the most important vital parts of the camera which consists one or more pieces of glass that focuses and frame an image within the camera. Lens control begins with an understanding of basic optics. A Lens is a curved piece of glass that causes Light rays to bend. Because glass is denser than air. Light glows down at the Point where it enters the Lens. Lenses bend light so that it can be controlled and Projected in Proper focus and size at a specific Point behind the Lens where a Light-Sensitive material can record or transmit the image. Simply Single Lenses fall into two basic categories: Concave and Convex.

Slide 11 : Concave Lenses which are thinner at the Center than at the edges bend Light rays away from the center of the Lens. On the other hand Convex Lenses are thickest at the center and bend light toward the center of the Lens. 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. The two basic features of Camera Lenses are their focal length and f stop ratings. The f stop is the ratio of focal length to the diameter of the lens. And focal length determines the “taking angle" of the lens. Lenses with short focal lengths are used for wide angle shot and Long Focal Length Lenses are called telephoto lenses. The lens fitted on most of the 35 mm camera covers an angle of 45°to 55° which is equivavalent to working angle of view of a human eye and called as “Normal or Standard lens”. The standard lens for 16mm size film is 20 mm.

Slide 12 : Angle of View Angle of View is the amount of a scene a photograph captures and can be measured vertically, horizontally or diagonally. 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. 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. The further away an image that a photographer is attempting to capture within their angle of view, the longer and more narrow the lens should be. For instance, a picture of the stars or far-off marine life would be taken with a longer, narrower lens than one that has an image with an angle of view that is twenty feet away. Similarly, if a photographer wants to include more or less light within an angle of view, they can use a petal or a hooded lens respectively.

Slide 13 : 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. The distances follow this formula:

Slide 14 : Points related to focal length of lens: Focal length controls magnification and also controls angle of view. A normal focal length lens also called standard lens, approximates the impression human vision gives. A normal lens has certain advantages over wide- angle or tele-photo lenses. Most normal lenses faster, compact, light weight and less expensive. Tele photo or long- focal-length lens provides greater image magnification and a narrower angle of view than a normal lens. Wide angle or short focal length lens increase the angle of view and shows more of scene than a normal lens from the same position. Wide angle lens have considerable depth of field. Zoom lenses are variable focal length lenses are popular because they combine a range of focal length into the camera.

Slide 15 : Terms related to Lens: 1- Optical Center: it is point on the lens through which the ray of light passed un-deviated. 2- Principle axis: it is a straight line passing through the centre of curvature of all the lens elements, and normal to the plane surfaces. 3- Focus: The rays of light parallel to the principle axis passing through the lens converge from a point (in case of convex lens) or seem to diverge from point (in case of concave lens) on the principle axis. This point is called Focus. 4 - Focal Plain: A plane passing through the focus of the lens horizontally to the principal axis is called the focal plane of the lens.

Slide 16 : Film chamber A pattern of black and metallic leak proof (light) squares on the cassette makes contact with contacts in the film chamber that pass information to the camera with regard to film speed, film type and film length The rewind crank: lets you wind your film back into the canister. It's usually on the left-hand-side, and more often than not has a little flip-out lever to make it easier to turn. The rewind release: allows you to rewind your film. Normally, while shooting the film is locked so that it can only move forwards and not backwards into the canister, for obvious reasons. The rewind release simply unlocks this safety mechanism. This is usually a small button located on the base of the camera. The ISO dial: which may be marked as ASA, tells the camera the speed of your film. This may not be a dial at all; it might be a series of button presses. Either way, this is necessary for cameras that have automatic exposure mechanisms, as different films will require a different exposure.

Slide 17 : PHOTOGRAPHIC FILM The discovery and invention of photographic film starts with one of those wonderful events in science: a complete accident. In 1727, a German scientist named Johan Heinrich Photographic film is a sheet of plastic (polyester, nitrocellulose or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution of the film. When the emulsion is sufficiently exposed to light (or other forms of electromagnetic radiation such as X-rays), it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing. Photographic film is photosensitive — it changes its properties when it’s hit by light. The trick of the photographer is to expose only certain parts of the film to the light. That’s the reason the camera goes “click” — the camera’s shutter is opening and closing very quickly to let in just a little bit of light to impact the film. That’s also why photographers develop their film in a “dark room” — they don’t want any extra light impacting the film until it is “fixed”. Keep that door closed!

Slide 18 : Black and white film has one light sensitive chemical emulsion sandwiched between transparent coatings. In black-and-white photographic film there is usually one layer of silver salts. When the exposed grains are developed, the silver salts are converted to metallic silver, which block light and appear as the black part of the film negative Colour film has three chemical emulsions, each sensitive to a different colour of light. Color film uses at least three layers.Typically the blue-sensitive layer is on top, followed by the green and red layers. During development, the exposed silver salts are converted to metallic silver, just as with black and white film. But in a color film, the by-products of the development reaction simultaneously combine with chemicals known as color couplers that are included either in the film itself or in the developer solution to form colored dyes. The image on undeveloped film is extremely faint — too faint to see, in fact. The stabilizing solution reacts with the silver compounds to make the image visible. After rinsing off the stabilizing solution, the developer next places the film in the fixing bath. The chemicals in the fixing bath react with the unexposed silver compounds, leaving only the image behind. After this step, the film is no longer sensitive to light. Now you can open the door.

Slide 19 : IMAGE SENSOR An image sensor is a device that converts an optical image to an electric signal. It is used mostly in digital cameras and other imaging devices. Early sensors were video camera tubes but a modern one is typically a charge-coupled device (CCD) or a complementary metal–oxide–semiconductor (CMOS) active-pixel sensor. Today, most digital still cameras use either a CCD image sensor or a CMOS sensor. Both types of sensor accomplish the same task of capturing light and converting it into electrical signals. A CCD is an analog device. When light strikes the chip it is held as a small electrical charge in each photo sensor. The charges are converted to voltage one pixel at a time as they are read from the chip. Additional circuitry in the camera converts the voltage into digital information. A CMOS chip is a type of active pixel sensor made using the CMOS semiconductor process. Extra circuitry next to each photo sensor converts the light energy to a voltage. Additional circuitry on the chip may be included to convert the voltage to digital data. Neither technology has a clear advantage in image quality. CMOS can potentially be implemented with fewer components, use less power and/or provide faster readout than CCDs. CCD is a more mature technology and is in most respects the equal of CMOS.

Slide 20 : CHARGE-COUPLED DEVICE (CCD) CCD sensors have been used in cameras for more than 20 years and present many advantageous qualities; among them, better light sensitivity than CMOS sensors. This higher light sensitivity translates into better images in low light conditions. CCD sensors are, however, more expensive as they are made in a non-standard process and more complex to incorporate into a camera. A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time. Technically, CCDs are implemented as shift registers that move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins. The device is integrated with a sensor, such as a photoelectric device to produce the charge that is being read, thus making the CCD a major technology where the conversion of images into a digital signal is required. Although CCDs are not the only technology to allow for light detection, CCDs are widely used in professional, medical, and scientific applications where high-quality image data is required.

Slide 21 : HOW CCD WORKS: In a CCD for capturing images, there is a photoactive region (an layer of silicon), and a transmission region made out of a shift register (the CCD, properly speaking). An image is projected through a lens onto the capacitor array (the photoactive region), causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A one-dimensional array, used in line-scan cameras, captures a single slice of the image, while a two-dimensional array, used in video and still cameras, captures a two-dimensional picture corresponding to the scene projected onto the focal plane of the sensor. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor (operating as a shift register). The last capacitor in the array dumps its charge into a charge amplifier, which converts the charge into a voltage. By repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages, which it samples, digitizes, and stores in memory.

Slide 22 : COMPLEMENTARY METAL–OXIDE–SEMICONDUCTOR (CMOS) Recent advances in CMOS sensors bring them closer to their CCD counterparts in terms of image quality. CMOS sensors provide a lower total cost for the cameras since they contain all the logics needed to build cameras around them. They make it possible to produce smaller-sized cameras. Large-sized sensors are available, providing mega pixel resolution to a variety of network cameras. A current limitation with CMOS sensors is their lower light sensitivity. CMOS sensors use multiple transistors to amplify and move the charge provided by incoming photons of light, enabling the pixels to be read individually. The CMOS manufacturing process uses standard semiconductor technology, which increases memory photo sites, lowers the production cost significantly, and can make integration simpler

Slide 23 : AdvantagesCMOS image sensors have improved by leaps over the last few years. Resolutions are now high enough and run at fast enough frame rates to enable advanced-camera features like electronic pan, tilt, and zoom or image stabilization. CMOS architecture allows for random pixel access and window-of-interest readout for applications requiring image compression, motion detection, or target tracking. CMOS imagers are now designed in to generations of DSCs, IP security cameras, and even intelligent vehicle systems. Their portability and low power consumption have driven these sensors to dominance in markets like mobile handset camera systems; digital SLRs; and high-speed, machine-vision cameras.  Features High dynamic range:High dynamic range sensors capture complete scene information, enabling sophisticated processing applications. Low-light and near-IR sensitivity:Acutely sensitive or near-IR sensors perform in very low-light, capturing seemingly obscured details. High speed:Speedy sensors running at fast frame rates open up a new world of advanced features like burst modes and improve standard features like auto focus.

Slide 24 : DIFFERENCE BETWEEN CCD & CMOS Both CCD (charge-coupled device) and CMOS (complimentary metal-oxide semiconductor) image sensors start at the same point -- they have to convert light into electrons. If you have read the article How Solar Cells Work, you understand one technology that is used to perform the conversion. One simplified way to think about the sensor used in a digital camera (or camcorder) is to think of it as having a 2-D array of thousands or millions of tiny solar cells, each of which transforms the light from one small portion of the image into electrons. Both CCD and CMOS devices perform this task using a variety of technologies. CCD sensors, as mentioned above, create high-quality, low-noise images. CMOS sensors, traditionally, are more susceptible to noise. Because each pixel on a CMOS sensor has several transistors located next to it, the light sensitivity of a CMOS chip tends to be lower. Many of the photons hitting the chip hit the transistors instead of the photodiode. CMOS traditionally consumes little power. Implementing a sensor in CMOS yields a low-power sensor. CCDs use a process that consumes lots of power. CCDs consume as much as 100 times more power than an equivalent CMOS sensor. CMOS chips can be fabricated on just about any standard silicon production line, so they tend to be extremely inexpensive compared to CCD sensors. CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality and more pixels.

Slide 25 : IRIS DIAPHRAGM / Aperture: The iris is the diaphragm, and the opening in the iris of the eye (the pupil) is the aperture. An analogous device in a photographic lens is called an iris diaphragm. 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. or 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. Or 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.

Slide 26 : SHUTTER: 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”. The earliest shutter was hardly more than a piece of card or tape held over the ‘lens’ or pinhole which was removed for a set period. The time normally ran into seconds or minutes due to the low sensitivity of film and the small apertures used. These shutters move slow (1 sec.,1/2 sec.) or extremely fast (1/1000 sec.), as per requirement of the situation. 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.

Slide 27 : Shutter Speed The Shutter Speed controls the amount of light by the length of time it remains opens. The faster the shutter speed, the more likely a moving subject will be sharp. Shutter and subject speed also affect the amount of blurring in a photograph.

Slide 28 : 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”. Shutter speed is the speed with which the camera’s shutter opens when the picture is taken and aperture is the size of the hole light passes through in camera lens before it gets to the shutter. it is important to control the amount of light to the film by using the aperture and shutter speed to get a correct exposure. Both the shutter speed and aperture affect the amount of light entering the camera. Shutter speed and aperture also affect sharpness. Things consider to choosing a shutter speed: 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. Fast moving subjects tend to need shutter speed of 1/250 of a second or faster into order to freeze motion or prohibit blur. The faster the subject needed faster shutter speed. Low level of light limit one to a slow shutter speed.

Slide 29 : Things consider to choosing a aperture: Choosing an aperture can dictate the amount of distance in front and behind your subject that is in acceptable focus. The larger the aperture number, the smaller the aperture hole, and the better the depth of field. The smaller the aperture number, the larger the aperture hole the less depth of field. Wide angle lenses,35mm-15mm have more depth of field per aperture. Tele photo lenses,80mm-200mm have less depth of field per aperture. Low level of light may require a large aperture hole. Co-relation of shutter speed and aperture hole: Slow shutter speed creates un- sharp pictures, hence requires tripod. Fast shutter speed freezes action and motion and creates sharp picture without Any tripod. Smallest aperture or hole gives best depth of field. large aperture or hole gives worst depth of field.

Slide 30 : Pentaprism A pentaprism is a five-sided reflecting prism used to deviate a beam of light by 90°. The beam reflects inside the prism twice, allowing the transmission of an image through a right angle without inverting it (that is, without changing the image's handedness) as an ordinary right-angle prism or mirror would. The reflections inside the prism are not caused by total internal reflection, since the beams are incident at an angle less than the critical angle, or minimum angle for total internal reflection. Instead, the two faces are coated to provide mirror surfaces. The two opposite transmitting faces are often coated with an antireflection coating to reduce spurious reflections. The fifth face of the prism is not used optically, but truncates what would otherwise be an awkward angle joining the two mirrored faces. A variant of this prism is the roof pentaprism which is commonly used in the viewfinder of single-lens reflex cameras. In this case, the image needs to be reflected left-to-right, as the prism transmits the image formed on the camera's focusing screen, which is itself reflected by the reflex mirror in the camera body. This reflection is done by replacing one of the reflective faces of a normal pentaprism with a "roof" section, with two additional surfaces angled towards each other and meeting at a 90° angle. This form of the prism changes the handedness of the image

Slide 31 : Memory (Internal & External) Digital camera memory is an essential and often overlooked piece of digital photography equipment. There are two types of memory in the camera one is internal memory or built-in memory and second is External memory. Internal Memory is the built-in memory. You can't alter it. Let's say a camera with 4 GB of internal memory, it means the camera has 4 GB of memory comes with the camera. if the camera has no SD slot for memory expansion then you're stuck with 4 GB, it's all you can get. Once you reach the 4 GB limit, you'd need to delete off files to gain back space.External memory is something like a SD card, you can physically plug it in to add more Although memory cards are reusable, they don't have a limitless capacity and it's always good to have more than you actually need.