Digital photo printing

Wednesday, 10 January 2007

Photography is an old and well known technology in which many advances in cameras and accessories have been made. With the rapid development of digital technology, image-capturing devices, such as digital still cameras, mobile camera phones, have become lower priced and more convenient in portability, and as a result, become an increasing part of people’s daily life. Digital cameras are rapidly replacing film cameras in many areas of photography. Digital printing technology has been used as a suitable replacement for traditional camera and photographic film techniques. Traditional methods of printing images from a developed roll of film onto a photosensitive media comprises passing a strip of developed film through an exposure gate where the images on the film are exposed onto a photosensitive media, such as photographic paper. Such photographic techniques rely upon a film roll having a number of pre-formatted negatives which are drawn past a lensing system and onto which is imaged a negative of a image taken by the lensing system. Upon the completion of a film roll, the film is rewound into its container and forwarded to a processing shop for processing and development of the negatives so as to produce a corresponding positive set of photos. Unfortunately, such a system has a number of significant drawbacks. Film processing techniques require the utilizing of a "negative" and its subsequent processing onto a "positive" film paper through the utilization of processing chemicals and complex silver halide processing etc. This is generally unduly cumbersome, complex and expensive. The chemicals utilized are obviously very sensitive to light and any light impinging upon the film roll will lead to exposure of the film. They are therefore required to operate in a light sensitive environment where the light imaging is totally controlled. This results in professional engineering requirements leading to increased expense. In contrast to conventional photographic cameras, digital cameras do not use film to capture an image. A digital camera varies from a film camera in that instead of taking pictures on film that must be developed, it takes pictures that are saved as image files within the camera. The image files may be saved on internal memory of the digital camera, or on a removable memory card or other computer-readable media that can be removed from the camera and inserted into a corresponding slot of a computer or a device attached to the computer. The image files are thus usually uploaded to a computer, where the user may manipulate them, and ultimately may print them on a printer.

The use of digital cameras has exploded in recent years. A large number of digital cameras of various designs and including different components are commercially available. The different digital cameras include different image acquisition sensors which converts light into electrical signals. These image acquisition sensors have different characteristics, in particular different spectral sensitivity. One of the most important technologies in digital photography is the implementation of two dimensional imaging devices such as CCDs (charge couple device) or CMOS (complementary metal oxide semiconductor) sensors in digital photography in general and in the body of standard camera format in particular. Digital cameras are equipped with a display such as an LCD, which functions as a view finder, and which allows a photographed picture to be reproduced and confirmed on the display without using any other devices. A digital still camera can take an electronic or digital image using the camera's image sensor and store the image digitally in some type of memory medium. The digital camera is configured to execute photoelectric conversion of image pickup light to provide image data, record the image data on a recording medium, and output the recorded image data to an external image processing system such as a personal computer (PC). The external image processing system performs print image data preparation processing and outputs the prepared print image data to a printer for printing or reproducing the picked-up image on paper. In the digital camera, an optical subject image is converted into an electronic image signal. Further, the electronic image signal is digitally converted for obtaining image data to be stored in a memory. Some of the digital cameras have a built-in printer to produce a photo print of the desired image data by means of hard copy. These cameras are desirable for consumers who do not own personal computers or feel uncomfortable using such computers. The command buttons and graphical user interface (GUI) menus on such a camera's liquid crystal display (LCD) are used in accordance with a preprogrammed protocol to select the images to be printed. The photo taken by the digital camera is stored in digital camera's memory unit such as the memory card in digital format. Presently, most digital cameras have rewritable memory built into the camera or provided in a removable storage media card, for example. The use of rewritable memory is advantageous because it allows the user to easily discard a stored image if it does not meet the user's requirement. By discarding the image, the image data is erased from the camera memory, which frees storage space for more images. Each photo has an image file corresponding to it. The image file is generally such as an image file in the JPEG compression format. The digital image file must be printed out to have a real paper photo. Digital still cameras permit high resolution color images to be stored for subsequent printing by conventional ink jet and laser printers. The quality of the color prints that are produced approaches that of conventional silver halide photographic prints. As the resolution of digital still cameras have increased, the quality of the digital image is now sufficient in many circumstances to displace photographs taken by conventional photographic film. As digital camera prices fall, digital image quality improves, and ease of use increases, more and more consumers will use digital cameras to fill their image capturing needs. Technological advances have enabled the development of digital cameras that rival the quality of film based cameras. Digital camera interfaces have been designed to mimic film camera controls so that knowledgeable photographers may control the picture taking functionalities, such as shutter speed, aperture, flash, zoom and other features.

The digitization of a variety of information and the preservation of such information by recording it on various recording media has been realized by the popularization of computers and devices that utilize them. Use of a digital camera enables a user to personally and easily preserve or process an image in various manners through use of a processing device such as a personal computer. Digital images transferred to the computer can be processed with the use of suitable programs and printed directly by a user. This eliminates the cost of films and developing, thereby reducing the time required to produce the photographs. Digital images transferred to the computer can be processed with the use of suitable programs and printed directly by a user. This eliminates the cost of films and developing, thereby reducing the time required to produce the photographs. Image data thus obtained using a digital camera of such a conventional technique are transferred to a personal computer that is connected to the digital still camera through a communication interface. There are many methods for printing images from digital cameras. Digital image files may be physically transferred to a computer via a memory card or by a data link between the computer and the digital camera. Once the digital image resides in the memory of the computer, a computer program can be used to select and print the images on a local printer. In the personal computer, various data processes desired by user are carried out. Digital images, whether obtained from scanned film or from digital cameras, often contain exposure errors, where the key subjects of the picture are lighter or darker than desired by the user, due to imperfect exposure determination algorithms in the digital camera or film scanner which created the digital image. The personal computers may be provided with digital still camera image processing software for enhancing the color balance, contrast, borders and other characteristics of the images prior to storage, printing or transmission. Many imaging applications, such as Adobe Photoshop, permit the user to adjust the "brightness", "contrast", and/or "gamma" of the image by sliding using one or more "sliders" controlled by a mouse. Each control adjusts one of the slope, x-intercept, or exponential function applied to the image, typically using a look-up table, in order to modify the tone reproduction of the image when it is displayed or printed. Thereafter, the processed data are transferred to a color ink-jet printer, color sublimation type printer, color copier, etc. and printed therein. The field of digital photography is growing rapidly because of the availability of inexpensive digital cameras and low cost personal computers to process the digitally acquired images. Digital printing is changing the printing industry. Advancements in printing technologies have enabled printers to vividly reproduce a wide range of colors at resolutions that rival traditional photographic prints. Improvements in editing and processing capabilities available with digital photography continually open doors to new forms of creative expression available to both the amateur and the professional.

Digital printers, which print images such as documents which are retained as data files in computers, are now commonplace in offices. In digital printing, a customer creates an electronic version of a document and sends it to a printer operator for final formatting, printing, and assembly on selected printing devices. In digital printing, digital image relating to an image desired to be printed is retained in a computer. In the standard model of digital printing, data to be printed is retained in the memory of a source computer, such as a print driver, print server, personal computer, or mainframe. When the data to be printed, in the form of a file, is sent from the source computer to a printer, the data is in a page description language or some other format. At the printer, software resident therein known as a "decomposer" or "interpreter" converts the file from its original page description language or format into code which ultimately operates the printer hardware, such as by modulating a laser or controlling an ink-jet printhead over time, to form the desired printed images. A digital printer may use a variety of different technologies to transfer colorant to the page. Some common types of digital printers include laser electrophotographic printers, LED electrophotographic printers, dot matrix impact printers, thermal paper printers; film recorders; thermal wax printers, dye diffusion thermal transfer printers, and ink jet printers. Use of ink-jet printing apparatus for creating color images based on digital image data is well-known. Basically, color ink-jet printing apparatus include printheads, or portion of a single printhead, each dedicated to placing ink at specific locations on a print sheet in accordance with the digital image data. In most basic digital color printers, the primary colorants available to be placed at various locations on the print sheet, which correspond to different types of signal accepted by the printing apparatus, correspond to the subtractive primary colors cyan, magenta, and yellow. An ink jet printing method is advantageous in that actuating noise is sufficiently low to the extent that can be ignored, and in being capable of high-speed recording, and thus is currently becoming preferred among recent printing methods. A typical laser printer usually includes an electrostatic printing mechanism composed of a cylindrical drum having an electrically charged surface. Toner particles of opposite charge adhere to the drum. The image to be printed is formed on the drum by means of a laser beam directed toward the drum. Wherever the laser impinges on the drum, the drum surface is discharged, creating an area in which the charged toner particles will not adhere, corresponding to white areas in the image. Solid areas are represented by the charged areas of the drum, where the toner particles adhere. The laser scans the drum line by line, emitting pulses that correspond to the white and black areas of the image. Subsequently, the image is printed to paper by transferring the toner on the drum surface to paper by means of a heating process. A color thermal printer is used with color thermosensitive recording paper, and produces full-color prints. The recording paper includes a support and at least three thermosensitive coloring layers overlaid thereon. While the recording paper is moved back and forth in the color thermal printer, a thermal head pressurizes and heats the recording paper to record three color images to the coloring layers. After the thermal recording, a photo fixer is driven to apply ultraviolet rays to the recording paper.

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