To view all the figures / graphics / illustrations for reference in this article, click here. Looking for a digital camera for use in exercising Abstract control? Well, the technological improvements in CMOS and CCD image sensors and the introduction of new high definition display and recording formats have certainly led to the introduction of many different models of digital cameras. Due to the wide variety of features and price, it is more difficult than ever to choose the best digital camcorder. While some models are better than others in exchange for the specific application for which the camera has been designed and the features that are needed. Because there are so many factors involved in choosing and as new models are often introduced, it is preferable to provide guidance for the evaluation of the model for a specific application. Then, as new models are available, can be compared with existing models on the basis of the guidelines. The purpose of this document is to provide guidelines that should be considered when evaluating the cameras for use in surveillance applications. These applications are those that would be used by the armed forces, police and investigative staff special stages of collection or make a new collection of electronic and generally include remote viewing. Although these guidelines are useful for understanding the important camera features before making their decision to buy camera, we suggest you do your own research on models available and, based on these guidelines, choose models that are supposed to provide the performance and conduct your own tests in real situations. You may know that other factors may be important for your specific application and the final decision is a compromise of these other factors. To monitor the optical image quality is of utmost importance. Camera resolution and sensitivity are key factors to consider, with a variety of related factors such as image and the pixel field of view, pixel size and frame rate, image stabilization, options for replacement lenses and interchangeability lens, integrated mode, digital zoom and view the resolution, user interface, video format, recording media, the gain manual mode infrared video compression, external audio input, the viewfinder, robustness and video compression. Camcorder Resolution Video resolution is influenced by several specific camera. And 'well known that high-definition camcorders, providing greater resolution than standard definition formats. However, it is important to realize that if the camera is used to record sequences of images that are then to be considered (and not just use your camera to display the video output in real time), both the optical resolution and the recording format must be considered in determining the resolution of the final video. Taken separately, the optical resolution depends not only on the size of the array detector, but also the image and the pixel field of view. Recording format also affects HD resolution. Finally, there are other factors that the resolution of May led to a revision to determine the maximum resolution of the camera. Detector Array Size: it seems that every camera uses a slightly different image detector. While the recording format can be HD 1280×720, 1440×1080, or 1920×1080, imaging detectors may vary slightly. As the table shows, for selected mid-range cameras, the detector array size can vary from single-chip cameras have arrays as large as 1920×1080 (Canon HF-10 and Sony HDRSR11) three blocks with chip detectors as large as 1440×1080. The physical size of the image sensor varies from camera to camera. Image and Pixel Field-of-View: As indicated in Table cons (see link above), the combination of the physical size of the camera's image sensor (eg 1 / 3 ") and its focal length (50mm for example ) leads to an image field of view (FOV) is defined as the angle of view from which the image information is received. There are different points of view corresponding to the horizontal and vertical directions according to the ratio of the image. For widescreen video formats, the vertical FOV is 9 / 16 of the horizontal FOV. All cameras have zoom lenses where the focal length range from wide angle (with the largest angular FOV) to a TV (with the small angular FOV). A smaller field-of-view results in a ratio of images at high magnification, as required for viewing small objects at a distance. Small angles of imaging sensors to create more restricted when used on the lens' focal length. For example, a lens of 50 millimeters provides a horizontal FOV of 5. 5 and 3. 7 ° when used with a 1 / 2 "and 1 / 3" format sensor, respectively. On the basis of the variation of the size of the detector and the focal length, field of view angle for different cameras varies accordingly. The image field of view can be established for all cameras based on a simple formula. Pixel FOV (also known as the instantaneous field of view or CVI) is a measure of resolution of an imaging system. Though related, the pixel of the image FOV and FOV are distinct and have a narrow FOV camera image does not necessarily have a corresponding pixel FOV restricted. As shown in the table (see link above), while the Canon camcorders are smaller and the values of the pixels of the image FOV, the Sony HDR-SR11 has a low pixel FOV, although the image FOV is almost twice those Canon. This calculator will FOV can be used to determine the values for the cameras FOV certain candidate. Pixel FOV is calculated that is the detection, identification and values formed in the range of recognition for some specified object to a specified distance. Recording Format: The difference between the various formats of HD recording is outside the scope of this document. However, the impact of the recording format for the resolution is essential for the performance of imaging for surveillance applications and is described here. As shown in the picture (we refer to the first link in this article), standard definition camcorders (with a ratio 4:3) recorded video with 480 horizontal lines per frame, which provides a resolution of 640 x 480. (This is for NTSC. PAL registered with 576 lines per frame offers a resolution of 640×576). Widescreen versions of this standard definition camcorder with a ratio of 16:9 are also available and recorded with a resolution slightly higher at 720 x 480 (720×576 for PAL versions). Due to limitations of recording format, it would be useful to have a high resolution CCD / CMOS sensor 720×480 pixels than a standard definition NTSC video camera, except in certain circumstances (such as the zoom view of the central pixel). However, with the introduction of higher resolution formats for recording, resolution detectors have a higher meaning. High definition camcorder sensitivity refers to the higher-resolution video in standard definition, and most often refers to the resolution is based on 720 lines per frame or 1080 lines per frame. Recording formats can be 1920×1080, 1280×720 and 1440×1080. As a result, are available with 720 or 1080 lines per frame recording formats with a resolution of 1280×720 and 1920×1080, respectively. It 'important to understand the recording format for all the cameras in question. If the resolution of the sensor is necessary to fulfill the monitoring function, then make sure that the camcorder records in sufficient resolution. This white paper has been on digital cameras, the discussion above the recording format was sufficient to describe the effects on image quality. However, since video takes up the movement, the fact that some cameras record "interlaced" video, while other records "progressive" video has some relevance, especially when the movement is important for the type of the checks. If not, then the amount of interlace vs. progressive scan is less important. Other factors Resolution: It is worth mentioning that in these three cameras that use of sensors, pixel technology gap was used horizontally to make incremental improvements to the sensor resolution by interpolation. This complicates the calculation of optical resolution, a bit ', but can not be an important factor. Camcorder low light sensitivity is usually of paramount importance to surveillance applications, especially when imaging at sunrise or sunset, but also in creating a module for night vision, that intensifies ambient light. The guidelines for the evaluation of the camera are listed below. It is advisable to consider the following factors: the minimum illumination specific advice, Lens F-number, the size of the pixels of the detector, the availability of night vision module. As such, the criteria for the comparison of these include: front lens F number, pixel size, noise reduction, it is clear that the performance of low light, as specified in the list of specific cameras cameras, because the individual in can produce variable results, even though the specifications may be similar. So once you've identified a number of different cameras that have the features of interest and the required performance, it is important to test the camera in low light capabilities. Recommended Specifications Minimum illumination: Very often, performance specifications in low light is provided on a sheet of specific camera. They are usually referred to as "low-light sensitivity" or "minimum illumination and the result is expressed in lux. The higher the lux rating is, the better the camera performs in low light conditions. However, because the data describing how these measures are made for low light are often not provided, it is extremely difficult to compare these data when comparing the different camera models from different manufacturers. (Which is supposedly the reflectivity of the objects being observed and what is the brightness of the image SNR? Etc.) As such, the use of these specifications is difficult and often unsatisfactory. And 'obviously preferable to test yourself camcorder. Some websites (such as www. Camcorderinfo. Com) conducted its own rigorous testing. The pixel size of the detector: not only the size of the array detector important, but the physical size of the detector is also important for a number of reasons. In most cases, a detector of small physical size (eg 1 / 6 "size) are in Camcorders less, while larger detectors (eg 1 / 3") are more powerful cameras. Physically detectors of small businesses in need of glasses, smaller and cheaper compact cameras because of cost. For surveillance applications, an important consideration is that the light sensitivity decreases with the size of the pixels. While the larger pixels generally have a higher sensitivity to light and are larger when imaging under poor lighting or at night, the larger pixels also translate into a reduction of resolution (in exchange for a lens focal length). Also, the more pixels, with a large table result in a wide range of important objectives. Thus, the smaller pixels are often preferable. We have to compare the sensitivity of the cameras with smaller pixels, with other camcorders under study. The pixel size for a range of digital cameras are presented in chart cons (compared to the first link in this article). Objective Lens F-Number: Like the SLR, Lens F-number is extremely important for the low sensitivity to light a video camera. All else equal, a lens with a low f-number (like F1. 4) devotes much of the light from the scene image sensors sensitive camera. A lens with an F-number that is twice as high (F2. will increase only 25% of light through it, which makes the camera 25% sensitive. That's a lot! For the compact camera with an integral lens, sometimes the front lens should be designed with a large F to maintain the relatively high number of compact design, yet deliver the desired zoom range. In particular, we note that the F-number increases as the values of focal length slightly. F-digit maximum zoom setting for a series of digital cameras are shown in the attached table. Night Vision Module Availability: video camera for use in surveillance applications, the availability of a module for night vision can be very important, especially for remote image and night. Cameras simply do not have the sensitivity to light enough to allow imaging in these environments. However, with the addition of a module for night vision, like those shown here, the camera's light sensitivity can be increased up to ten F-stop. As is known, the resulting image Night Vision will be green, in the absence of all colors. But images can be produced reasonable in light of the stars and the moon. Some of these modules for night vision can be viewed by clicking the link above. Other factors to consider in evaluating the cameras for surveillance applications, the resolution and sensitivity are usually the main considerations, other factors may deserve attention. Some of them are listed below. Media: "Media" refers to the point where the video will be stored. Many cameras use different types of media. The following are the most common types of media and some considerations for surveillance applications: MiniDV – These have been used for many years. The disadvantage is the need to fast forward and rewind, rather than direct access. However, they are known to be very reliable, are widely available and robust. Furthermore, it is often convenient to have a physical medium, with video surveillance rather than a single screen copy that could easily be lost or misunderstood. MiniDVD – Although family support can not be more comfortable as expected from the DVD often can not be directly inserted into the DVD player. Furthermore, recording in high quality sometimes results in a capacity much lower. Disk drive (HDD) – These are generally in favor of large capacity (for example 120 gigabytes) with a record time. Backup is of course important and necessary. Also note carefully that the compressed video is used to increase the storage capacity available. Flash Memory – Flash Memory (like semiconductor memory and smart card) is very interesting because there are no moving parts resulting in a compact design and efficient. The ability to increase every year. Image stabilization: Image stabilization is a camcorder feature that improves image quality, at the hands of video recordings, reducing blur caused by camera shake. Stabilizer corrects camcorder shake instantly so that the raid at telephoto (like the video taken from a moving vehicle) is smooth and regular. The image stabilizer can be optical or digital design. The optical image stabilizer usually manage a prism in order to stabilize the image projected on the detector camera. The digital image stabilizer usually means that the movement of the camera and taking advantage of additional rows and columns on the perimeter of the detector, moving images of an amount sufficient to stabilize certain types of movements. Normally, optical image stabilizer, although more expensive, are preferable because they better remove the obfuscation of the motion. Interchangeability of Objective: cameras cost much less, objective lenses are not removable. These lenses are compact and highly integrated in the body of the camera, have a wide range of focal lengths and even macro features. Normally, the field of vision of the integration of the zoom has been selected to achieve the desired FOV range for most applications. However, for greater versatility, higher end cameras have a lens and a removable frame so that a series of lenses may be available for a wider variation of applications, including wider viewing angle and more telephoto. (See the list of mid-range cameras with removable lens here). For non-removable lens cameras, so wide angle or telephoto lens FOV values are most needed, adapters are sometimes proposed to change the magnification as desired. But the result is a decrease in optical quality. For monitoring videographer, interchangeable lenses can be a great advantage if the magnification afforded by fixed cameras goal is not sufficient for the desired application. Moreover, the forms of night vision cameras that are designed for removable lens matching the lens and the camera and keep all the functions which the front lens "including motorized zoom, auto-iris and image stabilizer. Digital zoom: Digital zoom is an important element for any camera. Why can not assess the image sensor resolution on the camera's viewfinder or a billboard, digital zoom allows the operator to view the details on the viewfinder that otherwise unnoticed until digital images were then analyzed. It is also useful to note that a detector of an array of larger pixels allows the operator to make more than one zoom digital camera with a detector having a small size, without the effects of pixelization. UI: each machine operator to confirm that the characteristics of accessibility is of some importance. Drilling sub-menu after sub-menu to access the routine is not a desirable thing to do while in the field. Infrared modes: Some cameras have a sensitivity to the near infrared using an infrared illuminator to illuminate the scene. For various reasons, these beacons are not applicable to many situations of control. On the one hand, the illuminators normally with the camera is not enough to highlight the distances of interest. In addition, they can be detected by others with more cameras and CCD cameras. Manual Gain: For low light conditions, some cameras offer manual gain mode that allows the user to manually adjust the gain of the video image, typically increases by 18 dB. Although grainy for surveillance applications, video images are usually a significant improvement compared to non-vested or not self-bought versions. Shutter speed: whether to maintain the standard frame rates (eg 60 Hz) is not necessary because the observed objects move fast, the frame rate and shutter speed sensor can be reduced (eg to 1 / 3 sec) so that each pixel of the sensor will integrate light over a longer period to which they are exposed. In dark environments, choosing the longer time of integration acceptable may be sufficient to provide a usable image at dusk or dawn. External audio inputs: To prevent the occurrence of such a perspective of pure geek, remember that the audio quality and access to external audio input is important for video surveillance. The microphone does not always work well when shooting from afar, or if you need something more directional filters out background noise. Viewfinder: To carry out covert surveillance, with a viewfinder of the camera is sometimes important to prevent the illumination of the monitor. Durability: Another compromise is a serious lack of robustness in photographic equipment – switches and controls that fragile videographers stressful. When you're on the ground in conditions that are potentially dangerous, you do not want to play with some controls and LCD panels that come easily to hand. Price: Of course, the price is always a consideration in assessing the number of cameras are many models available today. But what these guidelines should show is that very often the most expensive camera, can not be better for specific applications questions. Understand what are the features most beneficial to the application, in view of the camera price range. Conclusion technological improvements in the field of CMOS and CCD image sensors and the introduction of new high definition display and recording formats have led to the introduction of different models of digital cameras. Guidelines were provided in the assessment of video cameras for use in surveillance applications. To monitor the optical image quality is of utmost importance. Camera resolution and sensitivity are key factors to consider, with a variety of related factors such as image and the pixel field of view, pixel size and frame rate, image stabilization, options for replacement lenses and interchangeability lens, integrated mode, digital zoom and view the resolution, user interface, video format, recording media, the gain manual mode infrared video compression, external audio input, the viewfinder, robustness and video compression. Although these guidelines are useful for understanding the important camera features before making their decision to buy camera, we suggest you do your own research on models available and, based on these guidelines, choose models that are supposed to provide the performance and conduct your own tests in real situations. You may know that other factors may be important for your specific application and the final decision is a compromise of these other factors. Disclaimer: We've tried to provide accurate information. However, we can not accept any responsibility for any errors or inaccuracies. If you find errors or need assistance, please contact us directly. Thank you. For the most complete White Papers to visit our center of competence. www. electrophysics. com / Night Vision 373 Route 46, Fairfield, NJ 07004 Tel: 973-882-0211 Fax: 973-882-0997 www. electrophysics. com © 2008 Electrophysics Corp. All rights reserved. ISO 9001:2000 Certified Company UKAS # 7096 – ANAB # A060693

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