The functional structure of the digital camera Fig.1.
Formation of images in the camera The flow of light from the subject passes through the lens to the light- sensitive element of the matrix (Figure 1). All these elements, or matrix cells differentiate brightness of light falling on them. The greater the amount of light falls on the light- sensitive element of the matrix, the greater the electrical charge formed on it. Once made frame (camera shutter button is pressed), formed on the matrix image is read, that is, different levels of electric charges are converted into the corresponding numeric values and act in the operational memory of the processor.
The processor processes each value of the quantities of charges of the matrix element and generates a graphic image in the form of dots with different colors and brightness. The file is then written to the memory card. If the matrix gets a lot of light, it will flare matrix and the processor will not be able to distinguish between shades and gradations of light and dark image of the object. If the matrix gets little light, the processor also can not distinguish between colors and gradations of light and dark image of the object. To ensure proper illumination of the matrix, ie, allow to distinguish between shades and gradations of light and dark image of the object using the adjustment value of the incident light flux to the matrix. This adjustment happens automatically when automatic shooting mode; or set manually before recording using the camera's aperture and shutter. Aperture - the hole in the lens. By varying the size of the holes can regulate the amount of light entering the camera. Shutter Operation determines the length of time during which the light penetrates into the camera and the lens focuses the light on the sensor and forms an image.
A block diagram of a digital camera Optical unit Flash unit Viewfinder unit Power Supply matrix Processor Memory card LCD USB порт Program Exposure meter gate diaphrag m
Aperture - the hole in the lens. By varying the size of the holes can regulate the amount of light entering the camera. Shutter Operation determines the length of time during which the light penetrates into the camera and the lens focuses the light on the sensor and forms an image. Assigning camera units Meter - measures the level of illumination of the subject and outputs the data to the processor to calculate the automatic exposure (sensitivity setting matrix, the aperture value and shutter speed). Viewfinder unit - designed for visual evaluation of the field size of the subject (frame size). flash unit - designed to further illuminate the subject, if the low level of illumination. The optical unit (lens) - provides a focus on the subject and controls the flow of light falling on the subject in the matrix. Adjusting the flow of light is provided by the aperture and shutter.
The light image formed by the lens of the camera is put into a recording device. In digital cameras in this role acts as an electron-optical converter (EOC), which is a matrix. Matrix - a device that is in contact with its light-sensitive area of the luminous flux generates and accumulates electric charge. One of the main characteristics of a digital camera is the resolution of the matrix. It is indicated in the form of a pair of numbers (the first number - the number of columns of the matrix, and the second - the number of its rows). Matrix of digital cameras A digital image is composed of dots, called pixels. The more pixels, the sharper the photo resolution, better image. MegaPixel (MP, one million points) is a characteristic of the resolution matrix capacity. In particular, at a resolution of 1600 x 1200 matrix is called a megapixel. Matrix cameras need to be cleaned periodically, especially if you often change the lens when shooting
The second of the main characteristics of the matrix is its sensitivity. Sensitivity matrix - the ability to respond to the incident light flux. Sensitivity matrix measured in ISO equivalent and usually has a relative value from 100 to 1600 or more. Power supply - stand-alone battery LCD - liquid crystal display enables you to view pictures taken, and the object rendering when shooting his crop. Processor - provides control of camera units in terms of setting the parameters for shooting, manufactures computing operations for setting the block parameters, analyzes based on measurements meter illumination level of the subject and generates data for calculations; generates an image file. Memory card - used to store image files. The program - The program provides all kinds of settlement of the processor associated with the formation of control actions, set the aperture, shutter speed, sensitivity matrix.
Data recording formats in digital cameras A digital image is recorded on the memory card is a sequence of numbers that indicate the brightness and color of each image point. Improving the methods of recording the graphic information has led to a variety of different standards or formats. Today, there are dozens of image formats, but used only four digital cameras! It: TIFF, JPG, RAW, and in extremely rare cases, the GIF. The main feature of digital records color images - they are very large, so the formation of pictures are compressed file. One of the most common graphic formats to JPEG uses compression. Thanks to the information compressed JPG image takes up much less space on the memory card than the same picture in the TIFF format. The picture with the five megapixel camera in JPG format takes only about 2 megabytes in TIFF format in eight times more, ie 16 megabytes.
aperture features If you change the current lens aperture diameter aperture controls the amount of light and depth of field of the subject. Depth of field - a part of the image, which is in the field of field from the front to the back of the picture. The aperture value designated aperture value. Each number of the lens aperture corresponds to the diameter of the aperture. The larger the aperture, the more light falls on the matrix in one and the same time. A small aperture (eg 16, a small hole diameter) will give the greatest depth of field, ie, and the foreground and background are sharp in the picture. In turn, for example, aperture 5.6, makes clear only the objects that are in the foreground. The background is out of field and, accordingly, will be blurred. Some of the diaphragm comprise the following sequence: 2.8, 4, 5.6, 8, 11, 16, 22, The most common values for the most part in the aperture - are values from 2 to 16.
Before the matrix is the shutter. Opening and closing, it is strictly metered amount of light falling on a matrix. Watergate formed an excerpt. What is the delay - the time from the opening until the closing of valve flaps for which the light has time to get to the photosensitive element of the camera. Modern cameras have a fairly wide range of exposure settings, which generally varies between 30 and 1/4000 second. Exposure choice depends primarily on the nature of the subject, and the degree of brightness of a subject. Faster shutter speeds (1/ /4000 sec) are mainly used for shooting moving images, fast-moving objects, sports events. When the subject is in motion or when the photographer causes the camera to move making sure, for example, close to the plane takes off. Slow shutter speed (1 -. 1/40 sec) is used usually in low-light conditions - indoors, at night or twilight. This excerpt is more suited to creative experiments - for example at city night photography, you can get colorful fiery plumes from passing cars along the street. Gate. Excerpt.
Exposure - a work-light image sensor on the lighting time. It is expressed in lux * s (for seconds suites). It is formed by a set of parameters established by the aperture, shutter speed and sensitivity matrix. One of the great features that can only be present in a digital camera is the automatic exposure. Thus practically the camera will automatically detects the light level and in accordance with it sets the shutter speed (shutter speed) and aperture value. Exposure However, you can not always trust the system automatically set the exposure. Some lighting conditions knock automatic adjustment system, then received either underexposed (too dark) or overexposed (very light) image. Therefore, to achieve high-quality texture mapping of objects taken or other small parts, in this case it will be impossible. Therefore, when shooting in unusual situations it is best to set the exposure manually.
Complete algorithm of digital camera - Direct the camera at the subject and set up the optical zoom (zoom) so that the object is closer or farther away; - Lightly press the shutter button; - The camera automatically focuses on the subject and evaluates the illumination; - The camera sets the shutter speed and aperture for optimal exposure; - The camera pans to the focal point of the screen and gives a signal of readiness to shoot; - Press the shutter button all the way; - The camera resets the previous settings of the matrix and creates an electrical charge before the shutter closes; - ADC (analog-to-digital converter) measures the charge and produces a digital signal which represents the amount of charge at each point (pixel); - A processor interpolates the data of different pixels to create natural color; - The processor performs data compression to a predetermined level and in a specific format (JPG or RAW); - Information stored on the memory card