What is the best camcorder for surveillance?

Posted on April 9, 2010, 6:52 am

To see all figures / maps / illustrations referenced in this article, click here. Summary Looking for a digital camcorder for use in monitoring the scene? Well, the technological improvements in CCD and CMOS sensors and the introduction of new high-definition viewing and recording formats have certainly led to the introduction of many different models of digital camcorder. Because of 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 return for the specific application for which the camcorder is designed and the features that are needed. Because there are so many factors involved in making a choice and that new models are often put in place, it is best to provide useful guidelines for the evaluation of models for a specific application. Then, as new models become available, they can be compared to existing models based on the same guidelines. The purpose of this paper is to provide guidelines that should be considered when evaluating camcorders for use in surveillance applications. These applications are those that would be used by law enforcement personnel and military special investigation gathering evidence or making a new electronic collection and generally include remote viewing. Although these guidelines are useful to understand the characteristics camcorder important before making your purchase decision camcorder, we suggest you do your own research on models available and, based on these guidelines, choosing the models that are expected to offer the best performance and conduct your own tests in real life situations. You can learn that other factors may be important for your specific application and your final decision is a compromise of these other factors. To monitor the quality of optical image is of the utmost importance. Camcorder resolution and sensitivity are key factors to consider, with a variety of related factors such as image and the pixel field of view, the pixel size and frame rate, image stabilization, options of replacement lenses and interchangeable lenses, integration method, the digital zoom and resolution display user interface, and video formats, recording media, manual gain, infrared remote, video compression, external audio input, the viewfinder, the robustness and video compression. Camcorder Resolution Video resolution is affected by a number of different characteristics camcorder. It is well known that high-definition camcorders offer a higher 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 available (rather than using the camcorder right to display the video output in real time), both the optical resolution and the recording format should be considered in determining the ultimate resolution video. Considered separately, the optical resolution depends not only on the size of the array of detection, but also the image pixel and field of vision. HD recording format also affects the resolution. Finally, there are factors other resolution that may warrant examination to determine the ultimate resolution camcorder. Sensor array size: It seems that every camera uses a different imaging detector. Although the format of HD recording can be 1280×720, 1440×1080 or 1920×1080, the imaging detectors may vary slightly. As the table shows, for selected mid-range cameras, the sensor array sizes can vary from single chip cameras with tables as large as 1920×1080 (Canon HF-10 and Sony HDRSR11) in blocks of three chips detectors as large as 1440×1080. The physical size of the imaging sensor also varies from camcorder to camcorder. Image and Pixel field of view: As shown in the accompanying graph (refer to the link above) the combination of the physical size of the camcorder’s imaging sensor (eg 1 / 3 “) and the focal length of its lens (50mm for example) result in an image field of view (FOV) is defined as the angle of view from which image information is received. There are different angles corresponding to the horizontal direction and vertical depending on the aspect ratio of the image. For wide screen video formats, the vertical field of view is 9 / 16 the horizontal FOV. All camcorders have zoom lenses where the focal length varies from wide angle (with the largest angular FOV) to a telephoto position (with the smallest angle FOV). The result is a small field of view in a higher magnification image is needed to bring small objects distance. The small imaging sensors to create angles closer when used on the same focal length. For example, a 50mm lens offers a horizontal field of vision. 5 5 and 3. 7 ° when used with a 1 / 2 “and 1 / 3 format sensor, respectively. Based on the variation of detector size and lens focal length, the angular field of view for different cameras varies accordingly. The field of view image can be determined for any camcorder based on a simple formula. The pixel (FOV also known as the instantaneous field of view or IFOV) is a measure of resolution of an imaging system. While related, the image and the pixel FOV FOV are distinct and a camcorder with image narrow field of vision does not necessarily have a corresponding pixel narrow field of vision. As indicated in the table (refer to above link ), while the Canon camcorders are smaller and the image pixel values FOV, the Sony HDR-SR11 has a pixel field of view in spite of a small FOV image that is almost two times larger than those from Canon . A calculator handy FOV can be used to determine values for FOV camcorders certain candidate. Pixel field of view is also calculated that is the detection, identification and recognition of values for certain sizes range specified object at a distance specified. Recording Format: The difference between the various formats of HD recording is beyond the scope of this paper. However, the impact of the recording format of the resolution is essential to the performance of imaging for surveillance applications and is described here. As shown in the figure (refer to the first link in the article), the standard definition camcorders (with a 4:3 aspect ratio) video recorded with 480 horizontal lines per frame that gives a resolution of 640 x 480. (This is for NTSC. PAL formats registered with 576 lines per picture with a resolution of 640×576). Wide screen versions of these standard-definition camcorder with a 16:9 aspect ratio also available and recorded with a slightly higher resolution of 720 x 480 (720×576 for PAL versions). Because of the limitations of recording format, it would have been useful to have a high resolution CCD / CMOS more 720×480 pixel detector in a standard definition NTSC video camera, except in certain circumstances (such as a picture to see the central pixel). However, with the introduction of more formats for recording resolution, high-resolution detectors sense . camcorder definition high sensitivity refers to video with higher resolution than standard definition and most often refers to the resolutions is based on 720 lines per image or 1080 lines / frame. Recording formats can be either 1920×1080, 1440×1080 and 1280×720. As a result, are available with either 720 or 1080 lines per image recording formats with a resolution of 1280×720 and 1920×1080 respectively. It is important to understand the recording format for any camcorder in the study. If full sensor resolution is necessary to fulfill the oversight function, then make sure the camcorder records in sufficient resolution. If this white paper focused on digital cameras, the above discussion of the recording format was sufficient to describe the effects on image quality. However, since the video resumes motion, the fact that some camcorders record “interlaced” video in other register “progressive” video has some relevance, particularly when the motion is important for the type of surveillance carried out. If not, then the relevance of interlaced vs. progressive scan is less important. Other factors Resolution: It is worth mentioning that in these camcorders that use three sensors, the pixel shift technology has been used in the horizontal axis to make incremental improvements to the sensor resolution using interpolation. This complicates the calculation of optical resolution a bit, but can not be a major factor. Camcorder low light sensitivity is generally important paramount to surveillance applications, especially when imaging at dusk or dawn, but also in the setting of a night vision module that intensifies ambient light. The guidelines for the evaluation camcorder are listed below. We recommend considering the following factors: the minimum recommended specification Enlightenment, Objective Lens F-number, detector pixel size, night vision module availability. As such, the criteria for comparing These include: F lens-number, pixel size, the noise reduction, it is evident that the performance of low light as shown in the list of specifications because different cameras camcorders can produce variable results, even if the specifications may be similar. Therefore, once you’ve identified a few different cameras that have the characteristics of interest and performance you need, it is important to test the capabilities of low light camcorder. Recommended Minimum Illumination Specifications: Very often, performance specifications for low light are provided on the sheet from a camcorder. They are usually described as either “low-light sensitivity” or “minimal lighting” and the result is given in lux. The higher the lux rating, the better the camera performs in low light. However, because the details describing how these measures are made low light is often not provided, it is extremely difficult to compare these figures when comparing different models of camcorders manufacturers. (Which is the reflectivity taken objects being viewed and what is the SNR? Image Brightness? Etc..) As such, the use of these specifications is complex and often unsatisfactory. It is obviously preferable to test yourself camcorders. Some websites (such as www. Camcorderinfo. Com) conduct their own rigorous testing. Detector Pixel Size: 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 (like 1 / 6 “size) are found in less expensive cameras while the larger detectors (eg 1 / 3″ format) can be found in camcorders, high performance. Physically small detectors require small lenses cheaper and result in compact camcorders at lower cost. For surveillance applications, an important consideration is that decreased sensitivity to light with the pixel size. While larger pixels generally have a higher sensitivity to light and are superior when imaging in low light or at night, more pixels also cause a decrease in resolution (in return for a particular focal length). Moreover, large size pixels wide range cause large pictures and large glasses. Thus, smaller pixels are often preferable. A comparison of the sensitivity of the cameras with the smallest pixels with other camcorders under study. Pixel sizes for a variety of digital camcorders are shown in the attached table (refer to the first link in the article). Objective Lens F-Number: As with SLR cameras, lens F-number is extremely important to lower camera sensitivity to light. All other things being equal, a lens with low f-number (such as F1. 4) focuses much of the light from the scene on the camcorder sensitive imaging detector. A lens with an F-number is twice as high (F2. will increase to only 25% of light through it, which makes the camcorder 25% as sensitive. It’s a lot! For compact cameras with integral lenses, sometimes the goal must be designed with an F-relatively high to maintain the compact design while providing the desired zoom range. In particular, we note that the number of F values at the focal length increases slightly. F-numbers at the maximum zoom setting for a variety of digital camcorders are shown in the attached table. Night Vision Module Availability: For camcorders to use for surveillance applications, the availability of a night vision module can be very important, especially for remote imaging and night. Camcorders simply do not have sufficient sensitivity to light to allow imaging in these environments. However, by attaching a module of night vision such as those presented here, the light sensitivity of the camcorder can be increased by a maximum of ten F-stops. As is known, the resulting image Night vision is green, in the absence of any color. But images can be produced reasonable in light of the stars and the moon. Some of these night vision modules can be viewed by clicking on the link above. Other factors to consider in evaluating the cameras for surveillance applications, the resolution and sensitivity are usually the primary considerations, other factors may merit attention. Some of them are listed below. Media: “Media” means the place where the video will be stored. Many camcorders use several different media types. The following are the common types of media and some considerations for surveillance applications: MiniDV – They have been used for many years. The disadvantage is the need to fast forward or rewind rather than direct access. However, they are known to be very reliable, they are widely available and robust. In addition, it is often convenient to have a physical with surveillance images rather than electronic copies that can easily be misplaced or mislabeled. MiniDVD – While media familiar, it may not be as practical as we wait for the DVD often can not be directly inserted into the DVD player. In addition, recording the highest quality sometimes results in a significantly lower capacity. Hard disk drive (HDD) – It is the media capacity is generally high (eg 120 GB) with a time record length. Backup is obviously important and necessary. Also note carefully whether the compressed video is used for storage in order to increase the available capacity. Flash memory – Flash (like memory and semiconductor memory cards) is very attractive because there are no moving parts resulting in a compact and efficient. Capacity is increasing every year. Image stabilization: Image stabilization is one factor which helps to improve picture quality camcorder when recording video devices, which reduces motion blur camera. The stabilizer corrects camcorder shake instantly so that hand telephoto shots (such as video taken from a moving car) are smooth and regular. These image stabilizers may be optical or digital design. Optical image stabilizers generally handle a prism in the objective to stabilize the image when projected on the camera detector. digital image stabilizers in general direction of the motion camera and taking advantage of additional rows and columns on the perimeter of the detector, moving image of an appropriate amount to stabilize certain types of movement. Normally, optical image stabilizers although more expensive, are preferable because they better remove the blurring component of the motion. Lens Interchangeability: Many camcorders have a lower cost non-removable objective lenses. These lenses are compact and highly integrated into the camcorder, a wide zoom range of abilities and even macro. Normally, the field of vision of the built-in zoom lens is chosen to obtain the desired FOV range for most applications. However, for added versatility, high-end camcorders offers a removable lens and lens mount, so that a whole series of lenses may be offered for a greater variation of applications, including wider viewing angle and telephoto more displayed. (See the list of mid-range cameras with removable ice here). For non-removable lens cameras, if a greater angle or telephoto more FOV values are needed, the adapters are sometimes offered to change the magnification as desired. But the result is a reduction in optical quality. For the videographer monitoring, interchangeable lenses can be a great advantage if the magnification offered by the fixed lens cameras is not sufficient for the desired application. In addition, night vision modules are designed for camcorders removable lens matching the lens and the camcorder and keep everything objective lens “including the power zoom functions, auto-iris and stabilization image. Digital zoom: Digital zoom is an important asset for any camcorder. Because it is not possible to assess the resolution of all imaging detectors on the camcorder’s viewfinder or display panel, digital zoom allows the operator to view details on the viewfinder that would otherwise go unnoticed until digital images were then analyzed. In addition, it is useful to note that a detector of a more pixel allows the operator to zoom over digital camcorders with smaller detector without the effects of pixelization. User Interface: Any camcorder operator will confirm that the accessibility features is of some importance. Drilling through the sub-menu after sub-menu to access the routine is not a desirable thing to do while in the field. infrared mode: Some camcorders have a sensitivity to near infrared light allows the use of infrared illuminator for illuminating scenes. For various reasons, these illuminators are not applicable to many monitoring situations. For one thing, the illuminators normally included with the camcorder does not throw sufficient light at the distance of interest. In addition, they can be detected by others with most camcorders and CCD cameras. Manual Gain: For low light situations, some camcorders offer manual gain mode, which allows the user to manually adjust the gain of the video image, generally increases to +18 dB. Although grainy, for surveillance applications, video images are normally a significant improvement compared to non-acquired, or self-acquired versions. Shutter speed: If maintaining the standard frame rate (eg 60 Hz) is not necessary because the objects under observation does not move quickly, the rate and shutter speed detector can be reduced ( eg for 1 / 3 sec), so that each pixel of the sensor will integrate light over a longer time they are exposed. In dark environments, selecting the longest integration time may be acceptable enough to provide a usable image at dusk or dawn. External Audio Inputs: To prevent the appearance of looking like a pure geek perspective, it is important to mention that the audio quality and access to external audio input is important for monitoring the videographer. The microphone does not always work well when you shoot images below or if you need something more directional to filter out background noise. Viewfinder: When you perform covert surveillance, with a viewfinder on the camcorder is sometimes important to avoid the illumination of the LCD. Robustness: Another compromise is the serious lack of robustness in the photo equipment – switches and controls fragile stress because videographers. When you are on the ground in conditions that are potentially dangerous, you do not want to play with some controls and LCD panels that come immediately to hand. Price: Of course, the price is always a consideration when evaluating the many models of cameras available today. But, what these guidelines should show is that very often the most expensive camcorder can not be the best for a specific application questions. Understand the functions are most beneficial to your application in consideration of the price range camcorder. Conclusion The technological improvements in CCD and CMOS sensors and the introduction of new high-definition viewing and recording formats have led to the introduction of many different models of digital camcorder. Guidelines have been provided during the evaluation of camcorders for use in surveillance applications. To monitor the quality of optical image is of the utmost importance. Camcorder resolution and sensitivity are key factors to consider, with a variety of related factors such as image and the pixel field of view, the pixel size and frame rate, image stabilization, options of replacement lenses and interchangeable lenses, integration mode, digital zoom and resolution display user interface, and video formats, recording media, the manual gain mode, IR video compression, external audio input, the viewfinder, the robustness and video compression. Although these guidelines are useful to understand the characteristics camcorder important before making your purchase decision camcorder, we suggest you do your own research on models available and, based on these guidelines, choosing the models that are expected to offer the best performance and conduct your own tests in real life situations. You can learn that other factors may be important for your specific application and your final decision is a compromise of these other factors. Disclaimer: We have attempted to provide accurate information. However, we can not accept any responsibility for errors or inaccuracies. If you find errors or need assistance, please contact us directly. Thank you. For white suits, visit our knowledge center online. www. Electrophysics. com / Night Vision 373 Route 46, Fairfield, NJ 07004 Phone: 973-882-0211 Fax: 973-882-0997 www. Electrophysics. com © 2008 Electrophysics Corp. All rights reserved. A company certified ISO 9001:2000 UKAS # 7096 – ANAB # A060693