By Nirmal Roshan &

Deepak Chakravarti

Camera Obscura

The camera obscura (Lat. dark chamber) was an optical device used in drawing, and one of the ancestral threads leading to the invention of photography. In English, today's photographic devices are still known as "cameras"

The principle of the camera obscura can be demonstrated with a rudimentary type, just a box (which may be room-sized, or even hangar sized) with a hole in one side. Light from only one part of a scene will pass through the hole and strike a specific part of the back wall. The projection is made on paper on which an artist can then copy the image. The advantage of this technique is that the perspective is accurate, thus greatly increasing the realism of the image

In camera terms, the light converges into the room through the hole transmitting with it the object(s) facing it. The object will appear in full colour but upside down on the projecting screen/wall opposite the hole inside the dark room. The explanation is that light travels in a straight line and when some of the rays reflected from a bright subject pass through the small hole in thin material they do not scatter but cross and reform as an upside down image on a flat white surface held parallel to the hole

Pinhole Camera

A pinhole camera is a camera in which the lens is replaced by an extremely small hole, pierced in very thin material. Light from a scene passes through this single point, producing a more-or-less sharp image on the rear of a light-proof box. The image is upside-down, as in a conventional camera with a lens

do - is the distance of the object (from the pinhole)di - is the distance of the image (from the pinhole)ho - is the height of the object, hi - is the height of the image

The smaller the hole, the sharper the image, but the longer the exposure required. Optimally, the size of the pinhole, or aperture, should be 1/100 or less of the distance between it and the screen

A pinhole camera's shutter is usually manually operated because of the lengthy exposure times, and consists of a flap of some light-proof material to cover and uncover the pinhole. Typical exposures range from 5 seconds to hours and sometimes days

Box Cameras

The box camera is, with the exception of the pin hole camera, a camera in its simplest form. The classic box camera is shaped more or less like a box

A box camera has a simple optical system, often only in the form of a simple meniscus lens. It usually lacks a focusing system (fix-focus) as well as control of aperture and shutter speeds. This makes it suitable for daylight photography only

The box cameras are the oldest class of photographic cameras. The first camera ever used for making persistent photographic images was the big wooden box camera used for experimental photography in the mid-1820s

From the beginning amateurs were participating in the photography business, at least as customers for photographic material. But traveling was expensive, and camera equipment was heavy, so that a camera was even not in the luggage of many rich travelers. Circumstances had changed at the end of the 19th century. Dry plates, roll film, drugstores with darkrooms to rent, material and infrastructure were given to support a wider spreading of

amateur photography

The Kodak introduced in 1888, the first commercially successful box camera for roll film -- the advertising slogan being ‘You press the button - we do the rest’

The Kodak Brownie, a long lasting series of classical box cameras using roll film

A camera where the photographer sees exactly the same image that is exposed to the film and can adjust everything by turning dials and clicking buttons. Since it doesn't need any electricity to take a picture, a manual SLR camera provides an excellent illustration of the fundamental processes of photography

‘SLR’ – Single lens reflexmeans that the same lens is used for viewing and taking pictures

A still film camera is made of three basic elements: an optical element (the lens), a chemical element (the film) and a mechanical element (the camera body itself). As we'll see, the only trick to photography is calibrating and combining these elements in such a way that they record a crisp, recognizable image

Most point-and-shoot cameras are fully automatic. Conceptually, automatic cameras are pretty much the same as fully manual models, but everything is controlled by a central microprocessor instead of the user

The central microprocessor receives information from the autofocus system and the light meter. Then it activates several small motors, which adjust the lens and open and close the aperture. In modern cameras, this a pretty advanced computer system

In 1981, Sony unveiled the first consumer camera to use a charge-coupled device for imaging, eliminating the need for film: the Sony Mavica. While the Mavica saved images to disk, the images were displayed on television, and the camera was not fully digital

The Kodak Professional Digital Camera System (unofficially named the DCS 100) was the first DSLR camera. It was mounted on a Nikon F3 body and released by Kodak in May of 1991

The image sensor employed by most digital cameras is a charge coupled device (CCD). Some cameras use complementary metal oxide semiconductor (CMOS) technology instead. Both CCD and CMOS image sensors convert light into electrons

CMOSCMOSCCDCCD

A CCD transports the charge across the chip and reads it at one corner of the array. An analog-to-digital converter (ADC) then turns each pixel's value into a digital value by measuring the amount of charge at each photosite and converting that measurement to binary form

CMOS devices use several transistors at each pixel to amplify and move the charge using more traditional wires. The CMOS signal is digital, so it needs no ADC

Once the sensor converts the light into electrons, it reads the value (accumulated charge) of each cell in the image. This is where the differences between the two main sensor types kick in:

CCD sensors create high-quality, low-noise images. CMOS sensors are generally 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 is lower. Many of the photons hit the transistors instead of the photodiode

CMOS sensors traditionally consume little power. CCDs, on the other hand, use a process that consumes lots of power. CCDs consume as much as 100 times more power than an equivalent CMOS sensor

CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality pixels, and more of them

Differences between the two types of sensors lead to a number of pros and cons

The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the pictures can be larger without becoming blurry or ‘grainy’

256x256 - Found on very cheap cameras, this resolution is so low that the picture quality is almost always unacceptable. This is 65,000 total pixels

640x480 - This is the low end on most "real" cameras. This resolution is ideal for e-mailing pictures or posting pictures on a Web site

1216x912 - This is a "megapixel" image size -- 1,109,000 total pixels -- good for printing pictures

1600x1200 - With almost 2 million total pixels, this is "high resolution." You can print a 4x5 inch print taken at this resolution with the same quality that you would get from a photo lab

2240x1680 - Found on 4 megapixel cameras -- the current standard -- this allows even larger printed photos, with good quality prints upto 5.25x8 inches

4064x2704 - A top-of-the-line digital camera with 11.1 megapixels takes pictures at this resolution. At this setting, you can create 13.5x9 inch prints with no loss of picture quality

The largest are the ones used in "medium format" cameras, typically via a "digital back" which can be used as an alternative to a film back. Because of the manufacturing costs of these large sensors the price of these cameras is typically over Rs. 10,00,000

Image sensors used in DSLRs come in a range of sizes

With the exception of medium format DSLRs, the largest sensors are referred to as "full-frame", and are the same size as 35 mm film; these sensors are used in quite expensive DSLRs such as the Canon EOS-1Ds Mark III, the Canon EOS 5D, the Nikon D700, and the Nikon D3

Most modern DSLRs use a smaller sensor commonly referred to as APS-C sized, that is, approximately 22 mm × 15 mm, or about 40% of the area of a full-frame sensor

Other sensor sizes found in DSLRs include the ‘Four Thirds System’ sensor at 26% of full frame, APS-H sensors at around 61% of full frame, and the ‘Foveon X3’ sensor at 33% of full frame

The sensors used in current DSLRs are much larger than the sensors found in digicam-style cameras, most of which use sensors known as 1/2.5", whose area is only 3% of a full frame sensor. Even high-end digicams such as the Canon PowerShot G9 or the Nikon CoolPix P5000 use sensors that are approximately 5% and 4% of the area of a full frame sensor, respectively

There is a connection between sensor size and image quality; in general, a larger sensor provides lower noise, higher sensitivity, and increased latitude and dynamic range

According to the U.S. survey results, more than two-thirds (68 percent) of professional photographers prefer the results of film to those of digital for certain applications including:

Film’s superiority in capturing more information on medium and large format films (48 percent)

Capturing shadow and highlighting details (45 percent)

The wide exposure latitude of film (42 percent)

According to a survey made by Kodak in 2007, 75 percent of professional photographers say they will continue to use film, even though some embrace digital

Digital point-and-shoot cameras have become widespread consumer products, outselling film cameras, and including new features such as video and audio recording

Kodak announced in January 2004 that it would no longer sell reloadable 35 mm cameras in western Europe, Canada and the United States after the end of that year

In January 2006, Nikon followed suit and announced that they will stop the production of all but two models of their film cameras: the low-end Nikon FM10, and the high-end Nikon F6

On May 25, 2006, Canon announced they will stop developing new film SLR cameras

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