21 Sep 08 Digital Camera - the Easy Way to Take Pictures
Author: Roberto Sedycias
In comparison to film cameras, digital cameras have number of advantages which includes displaying the image on the camera screen right after recording, a single small memory device can record thousands of images, records video with sound, provision to edit images, and above all storage capacity can be re-used by deleting the images. There are numbers of devices available that has in-built digital cameras like mobile phones, PDA`s etc. Specialized digital cameras are fit into astronomical devices like The Hubble Space Telescope.
Digitizing images on scanner and digitizing video signals are much older than making of still images using digital signals from an array of discrete sensor elements. It was then used for astronauts to provide onboard navigation information during their visit to planets. It provided the still photos of stars and planet locations during transit and also additional stadiametric information for orbiting or landing guidance while approaching planet.
Steven Sasson, an engineer at Eastman Kodak, attempted to develop first digital camera with solid state CCD image sensor chips. But it was just a technical exercise. The true digital camera was Fuji DS-1P developed in 1988. And the first commercialized camera was Dycam Model 1 in 1990. Then in 1991, Kodak launched its Kodak DCS 100. Else Casio QV-10 was the first consumer camera in 1995. Nikon D1, a 2.74 megapixel camera was the first digital SLR developed in 1999. And in 2003, Canon 300D, first 600 megapixel camera was launched.
There are various types of digital cameras available. For videos, there are professional video cameras which are used in television and movie production. Camcorders come with inbuilt microphone and a small liquid crystal display to watch video while recording and playback. One can get still photographs also with them. Webcams, attached to computers, can capture full-motion video and are also available with microphones or zooming ability.
In live-preview digital camera, there is an electronic camera that can be used to frame and preview before taking the photograph and also to review stored photographs. Many of such cameras can take motion pictures. Then the recorded images can be transferred to computer, printer or any other such device. USB mass storage device enables the camera to function as disk drive for computer and Picture Transfer Protocol is then used.
To use Firewire, storage device is removed from camera and inserted into other device. Compact digital cameras, small and portable with inbuilt flash, are easy to use, and images are stored using Lossy compression. They might be able to capture motion picture but that to a limit. Bridge or SLR like camera is higher-end-live-preview camera with more advanced features like superzoom lenses, takes movies with sound, etc. Digital rangefinder, a user operated mechanism, is capable to measure subject distance.
Apart from above mentioned digital cameras, there are other categories also. Professional modular digital camera systems are used in studios for commercial production. Line-scan camera systems, based on focusing mechanism, are used in industrial settings to capture images of constantly moving materials. They capture images at extremely fast with high image resolutions.
Most of the digital cameras come with pre-set modes for different applications. Data can be transferred through USB port, Firewire port, USB PTP mode and even through wireless connections like WiFi, Bluetooth etc. These data are mostly stored in Microdrives, Joint Photography Experts Group (JPEG), Tagged Image File Format (TIFF) and RAW. Formats for movies are AVI, DV, MPEG and MOV. Recently MP4 format is also developed. Digital cameras have small but powerful batteries to operate for enough length of time.
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20 Sep 08 The Magic Behind Digital Camera
Author: Harry Rockwell
A digital camera, as opposed to a film or videotape camera, uses an electronic sensor to transform images (or video) into electronic data. Modern digital cameras are typically multifunctional and the same device can take photographs, video, and/or sound.
In 2005, digital cameras are starting to push traditional film cameras out of many markets. Shrinking device sizes have recently allowed miniaturized digital cameras to be included in multifunctional devices, such as cell phones and PDAs.
Classification
Digital cameras can be classified into several groups:
* Professional video cameras such as those used in television and movie production. These typically have multiple images sensors (one per color) to enhance resolution and color gamut. Professional video cameras usually do not have a built-in VCR or microphone.
* Camcorders used by amateurs. These are a combination of camera and VCR to create an all-in-one production unit. They generally include a microphone to record sound, and feature a small LCD to watch the video during filming and playback.
Still cameras
Digital still cameras are generally characterized by the use of flash memory and USB or Fire Wire for storage and transfer.
Most have a rear LCD for reviewing photographs. They are rated in mega pixels; that is, the product of their maximum resolution dimensions. The actual transfers to a host computer are commonly carried out using the USB mass storage device class (so that the camera appear as a drive) or using the Picture Transfer Protocol and its derivatives.
All use a CCD (for Charged Coupled Device) which is a chip comprised of a grid of phototransistors to sense the light intensities across the plane of focus of the camera lens.
There has recently been some application of a second kind of chip, called a CMOS (Complementary Metal-Oxide Semiconductor) sensor, and this chip is often differentiated from a CCD proper in that it uses less power and a different kind of light sensing material, however the differences are highly technical and many manufacturers still consider the CMOS chip a charged coupled device. For our purposes, a chip sensor is a CCD.
* Standard Digital Cameras: This encompasses most digital cameras. They are characterized by great ease in operation and easy focusing; this design allows for limited motion picture capability. They have an extended depth of field.
This allows objects at multiple depths to be in focus simultaneously, which accounts for much of their ease of focusing. It is also part of the reason professional photographers find their images flat or artificial-looking. They excel in landscape photography and casual use.
* Digital SLRs typically have a sensor nine times larger than that of a standard digital camera, and are targeted at professional photographers and enthusiasts. They resemble ordinary professional cameras in most ways, with replaceable flash and lens components, which give the user maximum control over light, focus and depth of field.
They are also bulkier and more expensive than their casual-use oriented counterparts. They are superb for portraiture and artistic photography because they can be customized for various applications with a comprehensive range of exchangeable lenses.
Professional modular digital camera systems
High-end digital camera backs used by professionals are usually separate devices from the camera bodies which they are used with. (This is because most of the large- and medium-format camera systems in professional use at the time that digital capture overtook film as the professional’s medium of choice were modular in nature, i.e. the camera body had multiple lenses, viewfinders, winders and backs available for use with it to fit different needs.)
Since the first backs were introduced there have been three main methods of “capturing” the image, each based on the hardware configuration of the particular back.
The first method is often called “Single Shot,” in reference to the number of times the camera’s sensor is exposed to the light passing through the camera lens.
Single Shot capture systems use either one CCD with a Bayer filter stamped onto it or three separate CCDs (one each for the primary additive colors Red, Green and Blue) which are exposed to the same image via a beam splitter.
The second method is referred to as “Multi-Shot” because the sensor is exposed to the image in a sequence of three or more openings of the lens aperture. There are several methods of application of the multi-shot technique.
The most common originally was to use a single CCD with three filters (once again red, green and blue) passed in front of the sensor in sequence to obtain the additive color information.
Another multiple shot method utilized a single CCD with a Bayer filter but actually moved the physical location of the sensor chip on the focus plane of the lens to “stitch” together a higher resolution image than the CCD would allow otherwise. A third version combined the two methods without stamping a Bayer filter onto the chip.
The third method is called “Scan” because the sensor moves across the focus plane much like the sensor of a desktop scanner.
These CCDs are usually referred to as “sticks” rather than “chips” because they utilize only a single row of pixels (more properly “photosites”) which are again “stamped” with the Bayer filter.
The choice of method for a given capture is of course determined largely by the subject matter. It is usually inappropriate to attempt to capture a subject which moves (like people or objects in motion) with anything but a single shot system.
However, the higher color fidelity and larger file sizes and resolutions available with multi-shot and scan-backs make them attractive for commercial photographers working with stationary subjects and large-format photographs.
Webcams
* Webcams are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.
These devices range in price from very inexpensive to expensive higher-end models; many complex webcams have a servo-controlled base capable of tracking facial motion with the help of software.
Interpolation
Image color or resolution interpolation is used unless the camera uses a beam splitter single-shot approach, three-filter multi-shot approach, or Foveon X3 sensor.
The software specific to the camera interprets the information from the sensor to obtain a full color image. This is because in digital images, each pixel must have three values for luminous intensity, one each for the red, green, and blue channels. A normal sensor element cannot simultaneously record these three values.
The Bayer filter pattern is typically used. A Bayer filter pattern is a 2×2 pattern of light filters, with green ones at opposite corners and red and blue elsewhere.
The high proportion of green takes advantage of properties of the human visual system, which is determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation.
Sometimes a 4-color filter pattern is used, often involving 2 different hues of green. This provides a wider color gamut, but requires a slightly more complicated interpolation process.
The luminous intensity color values not captured for each pixel can be interpolated (or guessed at) from the values of adjacent pixels which represent the color being calculated.
In some cases, extra resolution is interpolated into the image by shifting photosites off of a standard grid pattern so that photosites are adjacent to each other at 45 degree angles, and all three values are interpolated for “virtual” photosites which fall into the spaces at 90 degree angles from the actual photosites.
Connectivity
Many digital cameras can connect directly to a computer to transfer data. USB is the most widely used method, though some have a Fire wire port.
Integration
Some devices, like mobile phones integrates digital cameras. Mobile phone cameras are much more sold than standalone digital ones.
Digital cameras need memory to store data. The higher one goes in pixel size, the more memory will be needed. Cameras use a removable memory card to store data, but the cheapest and smallest cameras may simply use fixed internal memory instead. Some cameras come with inbuilt memory as well.
Autonomous devices
An autonomous device, such as a PictBridge printer, operates without need of a computer. The camera connects to the printer, which then downloads and prints its images. Some DVD recorders and television sets can read memory cards too.
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20 Sep 08 Digital Camera Basics - Want To Stop Being An Idiot And Learn How Digital Cameras Work?
Author: Mike Singh
With the advancement of the digital camera and the software that is made for them, most pictures look professional from the first click of the camera. But like most things, it is important to understand the “how and why” for higher quality results.
The basics of a digital camera revolve around terms like pixel, pixel count, white balance, sensor, sensitivity, optical zoom, or digital zoom. These improve your understanding of what digital photography is all about, and will help you become a more efficient photographer.
For example, one important term is digital sensor. A typical digital camera may have a digital sensor element that is as big as a small finger nail. Most 5MP digital cameras use a sensor that is 7mm x 5mm in size. This is much smaller than the size of the negative of a 35 mm camera. However, high-end digital cameras have large sensors, and generate superior images. These are important things to know, to see how pictures can be better or worse.
Digital cameras also have sensitivity settings similar to ISO ratings on film. Most digital cameras will have settings for sensitivity equivalent to ISO 100 and ISO 200. Many also have a setting for ISO 400. A few expensive digital SLR cameras with large sensors have settings for ISO 3200 or even for ISO 6400.
Most digital cameras have an optical and a digital zoom. An optical zoom lens works by changing the focal length and magnification while the zoom is being utilized - with the image quality remaining high. Digital zoom works by cropping the image to a smaller size. The cropped image is enlarged to fill the frame, causing a significant loss of quality.
The manufacturers of digital cameras use the term “pixel count” to describe their camera’s image properties. The word pixel originates from “(PIC)ture (EL)ement”- with the use of phonics added for emphasis. It represents a single point in a graphic image - not a dot but an abstract sample that can be reproduced in any size, without a dot or square appearance.
A pixel is important to understand because it is the basic unit of measurement, used to define a digital photograph. The more the number of pixels per square inch, the higher the resolution of a digital picture, increasing its clarity. Some examples would be 2,400 pixels per inch, 640 pixels per line, or spaced 10 pixels apart. Designers, artists, and photographers sometimes interchange the pixel terminology, such as dots per inch (dpi) with pixels per inch (ppi). The dpi is used when it refers to the printer’s resolution for the printing density. Each pixel is made up of three color channels - red, green and blue-and has a numerical value of between 0 and 255.
The pixel count also decides the size of a print in case you want to print photographs. A 3MP camera can provide excellent 4×6 inch prints, while a 4 or 5MP digital camera can deliver high quality 8×10 inch prints. With a digital camera you can pick the white balance to suit the light source. This is meant to ensure that white looks white, and not yellow or blue. Normally, your digital camera will do this automatically. You can also set the white balance yourself for better effects.
Since each pixel generates three bytes of data, a photographer using a 3MP camera will need a storage space of 9 million bytes or 9MB to store a single image. This is a huge amount of space. Camera companies therefore allow for a compression of image using a format called JPEG. This reduces the file size significantly but while doing so a lot of data is lost. To overcome this problem companies have come up with different storage formats. Canon calls it RAW while Nikon calls it NEF. The data loss is less in these formats.
The low end cameras used by beginners can shoot images whose pixel count is one million is categorized as 1 MP or one million pixel camera because the intensity of each pixel is variable, with each pixel having three or four dimensions of variability - such as red, green and blue, cyan, magenta, yellow, and black. The high-end cameras used by professionals, can range from 14MP to 22MP with a pixel count as high as 14 million or 22 million per image.
The thing to remember is the higher the resolution, the more realistic the image is, matching closest what the actual image is. So take your time, do some research, and talk to people who know cameras. Otherwise, a lot of money will be spent on something that is barely adequate for what you want.
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