Bstract
Looking for a digital camera to use for tracking? Now, the improvement of CMOS image sensors and CCD and the introduction of new high-definition displays and recording formats are certainly models of technology has led to the introduction of many digital cameras. The big differences in price and design points, is more difficult than ever to the optimal digitalcamcorders. Of course, some models are better than others, taking into account the specific application for which commemorated the camera and the functions that are necessary. Because there are so many factors in the choice and because the new models are often involved, it is recommended that guidelines for the evaluation of useful models for a particular application. Then, as new models are available, can be compared to current models on the same basis Guidelines.
The objective of this work is to develop guidelines that, while considering the cameras for use in surveillance applications provide. These applications are those that would be used by military, law enforcement personnel and special investigative methods for gathering evidence or the implementation of electronic reporting and typically include watching from a distance. While these specifications are useful to understand the importance of data, video camera, his right to> Camera purchase decision, we recommend that you search using the guidelines and templates available on the basis of this, the choice of models, the situations are designed to offer the best performance and conduct their own tests in real life. You can learn that other factors may be important for your specific application and the final decision is a compromise between these other factors.
To monitor the quality of the optical image is of paramount importance. camcorder Resolution and sensitivity must be considered the primary factors, with a variety of factors such as image and the pixel field of view, the pixel size and frame rate, image stabilization, alternative lens and interchangeable lens options, how to integrate, Digital zoom and resolution, user interface, video formats, storage media, manual gain, the infrared mode, video compression, external audio inputs, viewfinder, robustness and video compression.
camcorders Resolution
The video resolution is influenced by a variety of different camera features. It 'is known that the definition video cameras with higher resolution than the standard high-definition formats deliver. It 'important to recognize, however, that if the camera) to record image sequences, the time will be seen later (instead of the camera just about the video output in real terms, both the optical resolution and registrationFormat should be considered in determining the ultimate resolution of the video. Considered separately depends not only on the optical resolution of the detector array size, but also the image pixel and field of view. HD recording format also affects the resolution. Finally, there are other factors that may warrant termination contribution to the solution to determine the final camera.
Array detector size:
It seems that any camcorder uses a bit ' various imaging detector. While the recording format HD 1280×720, 1440×1080 or 1920×1080 may be, the image detectors vary a bit '. As shown in the table for a selection of mid-range camcorder that can vary in size detector array of single-chip cameras with array size of 1920×1080 (Canon HF-10 and Sony HDRSR11), and detectors with a three-chip devices as large as 1440×1080. The physical size of the image sensor varies from cameraCamcorders.
Image and pixel Field of View:
Image as shown in the table (refer to the link below), the combination of the physical dimensions of the camera's imaging detector (such as 1 / 3 ") and the focal length of objective lens (eg 50 mm), resulting in a field of view (FOV), as the angle of view from which information is received image. There are separate corner, corresponding to the horizontal and verticalDirections depending on the aspect ratio of the image. For wide screen video formats, the vertical field of view 9 / 16 of the horizontal FOV. Some camcorders have zoom lenses, in which the focal length from wide-angle (angle with the largest FOV) to a telephoto lens (with the smallest angle FOV) varies. A small field of view leads to a higher magnification image, as would be required to see small objects at a distance can.
Panel detectors provide a smaller viewing angle closerwhen used with the same focal length. For example, a 50 mm lens provides a horizontal field of view of 5.5 ° and 3.7 ° when a 1 / 2 "and 1 / 3" format or detector used. On the basis of the change in the size of the detector and the focal length, field of view varies depending on camera settings. The image FOV formula can be easily determined for each camera one.
The pixel field of view (also known as the instantaneous field of view or IFOV) is a measure ofResolution imaging system. Although, image, or field of view FOV is different pixels and a video camera with a narrow image FOV is not necessarily a narrow field of view corresponding pixels. As shown in the table (refer to the link below), while the Canon is the smallest pixel image and FOV values are, the Sony HDR-SR11 has a smaller pixel field of view, despite the image FOV, almost twice Canon is wider.
A handy FOV calculator, you can change the FOV values are determinedcertain candidate for the cameras. Pixel field of view is also expressed in the identification of detection and sensing of some specified object sizes are fixed at a distance.
Recording format:
The difference between the various formats of HD recording is beyond the scope of this paper. However, the effect of the recording format on a resolution critical of the quality of the images for surveillance applications and is described here.
As shown inFigure (a reference to the link below), including standard-definition video camera (with a 4:3 aspect ratio) video at 480 horizontal lines per frame, resulting in a resolution of 640 x 480 (This is for the NTSC format. PAL Format 576 lines per frame, which has a resolution of 640×576). Wide-screen versions of these standard-definition camcorder with an aspect ratio of 16:9 were also present and recorded with some great resolution of 720 x 480 (720×576 for PAL versions). Because ofFor the recording format, it would not) have proven useful pixel has a high-resolution CCD / CMOS detector larger than 720×480 pixels in NTSC standard definition video camera, except in certain circumstances (such as zoom in the central view. But with the 'introduction of recording formats for higher resolution, higher resolution detectors sense.
Camera sensitivity
High definition refers to video with a resolution greater thanstandard definition, and very often the decision is related to a 720 lines per frame or 1080 lines / frame-based. Recording formats can be either 1920×1080, 1440×1080 and 1280×720. Consequently, both lines with 720 or 1080 for recording formats of images with a resolution of 1280×720 and 1920×1080 respectively. It 'important to understand the recording format in exchange for all camcorders. If the full resolution of the sensor is required to carry out monitoringFunction, then make sure that the camera records in sufficient resolution.
If this paper is on digital cameras, the above discussion would have been sufficient recording format to be asked to describe the effects on image quality. Such as motion video, the fact that some cameras have a record interlaced video, and other video "progressive" has some significance, especially when the movement is important, the type of monitoring carried out include. IfNot, then the relevance of interlaced vs. progressive scan is less important.
Other factors, resolution:
It is worth remembering that the camera uses three sensors, the pixel-shift has been used in a horizontal incremental improvements to the sensor resolution, to be carried out by interpolation. This complicates the calculation of the optical resolution is a bit 'but not can play a major role.
Camcorder low light sensitivityusually is of primary importance for the monitoring of applications, especially in the figure rose in the dusk or dawn, but also in ensuring a form of night vision, the ambient light. The guidelines for Camcorder Reviews are listed below. We recommend starting a review of the following factors: the specific minimum recommended lighting, lens f-number, size in pixels of the detector, night vision equipment availability module.
As such, however, allow comparison of theseincluding: lens f-number, pixel size, electronic noise suppression, it is clear that performance in low light conditions, such as a list of specific cameras because the different cameras produce different results, even though the specifications may be similar.
Therefore, when you need to find a few different camera that it is of interest and benefit, is the most important for the camera in low light conditionsSkills.
Recommended minimum specification of lighting:
performance specifications are often made available to low-light sheet specifications a camera. These are usually either "low-light sensitivity" or "Minimum Illumination" and the result is described specified in lux. The lower the lux rating, the better the camera is low light. Since, however, describe the details of how these measures are made in low light, it is often notis provided, it is extremely difficult to compare the data from this comparison of different models of cameras from different manufacturers. (What is the reflectivity of the objects allegedly seen? What is the signal / noise? Brightness? Etc.) As such, the use of these data is complicated and often unsatisfactory. Of course it is best to test the same camera. Some sites (like camcorderinfo.com) conduct their own rigorous tests.
DetectorPixel size:
Not only the size of the array detector is important, but the physical size of the detector is important for several reasons. The majority of small quantities detector physics (eg 1 / 6 "format) in less expensive camcorder available while larger detectors (eg 1 / 3" format) found in a higher power cameras. Physically small size detectors require smaller, less expensive, and slow performance in a compact, affordable camera. For monitoring applications, an importantConsideration is that the sensitivity decreases as the pixel format. While larger pixels generally have more sensitivity to light and are higher when the result of images in low light or at night, more pixels and a decrease in resolution (in the light of a particular focal length). Even larger pixel, with results in large format arrays of arrays of large size and large lenses. The smaller the pixels are often preferable. You should compare the sensitivity of the camera with the smallest pixels with otherCamcorder considered. pixel sizes for a variety of digital cameras are in the table attached (see link below).
Lens F-Number:
As for the camera, lens f-number is extremely important for low-light sensitivity of the camera a. All other things equal, a lens with a low F number (eg F1.4) focused much of the light-sensitive imaging detector of the scene on camera. A lens with a number of F-is twice as high (F2.8), will be only 25% of the light, so that the camera is 25% sensitive. That's a lot! For compact cameras with built-in lenses, the lens sometimes has to be developed with a relatively high number of F to maintain the compact size yet deliver the desired zoom range. In particular, we find that the number of F values increased slightly longer focal length. F numbers at maximum zoom for a wide range of digital camerasare in the table attached (see link below).
Night Vision Module Availability:
using a video camera for surveillance applications, the availability of a form of night vision can be very important, particularly for imaging at a distance and at night. Camcorders not only allow enough light sensitivity for imaging in these environments. But with the addition of a form of night vision, like on our websitehttp://www.electrophysics.com/night-vision, camera's light sensitivity can be increased from ten stations on well-known is F. How to produce images, the green night vision is the lack of all colors. But it has also produced a reasonable image in starlight and moonlight are. Some of these forms of night vision can click on the link below.
Other factors to consider
In the evaluation of video cameras for surveillance applications, resolution andSensitivities are usually the main considerations are probably other factors that deserve attention. Some of them are listed below.
Media: "Media" refers, in which the videos are stored. Many camcorders use a variety of media types. The following are the most common types of media and some considerations for surveillance applications:
MiniDV tape – These have been used for many years. The disadvantage is the need to rewind before and, instead of direct access. However, they are knownquite reliable, are widespread and robust. Moreover, it is often useful to physical media with video surveillance in place of a soft copy only the light can be installed or need to be misunderstood.
MiniDVD – Even if half the family, can not be comfortable as you would expect were used for the DVD is often not directly on DVD. Moreover, the inclusion in the highest quality sometimes to a much lower capacity.
Hard Disk Drive (HDD) – This isgenerally supports high-capacity (eg 120 GB) with long recording times. Backup is certainly important and necessary. Note carefully, even if the compressed video is used for storage, to increase the available capacity.
Flash memory – Flash memory (such as solid state memory and memory card) is very interesting because there are no moving parts resulting in a compact and efficient. The capacities are increasing every year.
Image Stabilization:
ImageThe stabilization is a function of the camera, exercise improves the image quality of video recordings of hand, fading from the camcorder. Stabilizer corrects camcorder shake now and then the hand held telephoto shots (such as video-car made from a movement) are continuous and smooth. This image stabilizers may be optical or digital design. Optical image stabilizer usually manipulate a prism through the lens to stabilize the image when projected ontoCamera detector. Digital image stabilization in the control and direction of movement of the camera, taking advantage of the other rows and columns on the periphery of the detector, which move in the same amount to stabilize the movement of certain image. Typically, the optical image stabilizers, although expensive, are preferable because they better remove the uncertainty component of the movement.
Interchangeable Lens:
Many cameras have a lower cost non-removableLenses. These lenses are compact and highly integrated into the body of the camera have a very wide zoom range, and even the macro capability. Normally, the field of integrated view zoom selected the order most of the applications you want to reach the field of view. But for the most versatile camera with a lens of high-end and a detachable bayonet, so that a series of objectives for a greater variety of applications, including the widest angle, and much more can be offeredTelescopic viewing. (See a list of mid-range camcorder with interchangeable lenses here). Camcorder lens for non-removable when more wide angle or telephoto lens FOV values are required, are sometimes offered adapter to change the magnification as desired. But the result is a decrease in optical quality. For videographers monitoring can change the lens to be a great advantage when the magnification is provided by fixed lens cameras, not enough for the desired application. In addition, the nightThe modules Vision camera for the adaptation detachable lens between the lens and camera lenses and keep all the "functions such as motorized zoom, iris and image stabilization.
Digital Zoom:
Digital zoom is an important feature for the cameras. Why can not estimate the detector panel Resolution Imaging camera viewfinder or display, digital zoom allows the operator toDetails of the viewfinder, which would otherwise have gone unnoticed, were subsequently evaluated for digital images. It is also worth noting that the more a pixel detector array allows the operator to comply more like a digital zoom camera with a smaller sensor without the effects of pixelization.
User Interface:
Each camera operator has confirmed that accessibility features are of particular importance. Drill down menuafter sub-routine functions of access is not a desirable thing to do while on the ground.
IR mode:
Some cameras have a near-infrared sensitivity allows the use of an infrared lamp to illuminate the scene. For a variety of reasons, these lamps are not applicable to many control situations. First, usually the illuminator, the camera does not give light enough for the distances ofInterest. They can also be detected by others, with more cameras and CCD cameras.
Manual:
For low-light situations, some cameras offer a manual mode to win for the user to manually adjust the gain makes the video image, usually increases up to +18 dB. Although grainy, monitoring applications, video images is usually a significant improvement over not wholly obtained and auto versions.
Shutter speed:
IfThe maintenance of the standard frame rate (eg 60 Hz) is not necessary because the objects under observation are not fast in moving, the frame rate and detector reduces the shutter speed (for example, 1 / 3 sec), in integrate so that each pixel of the sensor can be exposed for an extended period that they face. In dark environments, the selection of the longest integration time acceptable enough to provide a usable image at dusk or dawn.
External audio input:
For the look and sound like a pure optical to prevent outsiders, it is important to remember that the audio quality and access to external audio inputs is important in controlling cameramen. The built-in microphone is not always well away when the images taken, or if something more directional filter out ambient noise must.
Viewfinder:
In carrying out covert surveillance, with a viewfinder camerasometimes important to prevent the light from the bright LCD screen.
Strength:
Another compromise is the serious lack of robustness in camera hardware – switches and controls fragile, causing stress cameramen. If you are traveling in the box in potentially dangerous conditions that do not want the game with few controls and LCD panels, which are easily detached from each other.
Price:
Of course the price is always aAccount in the assessment of many, many models of cameras already available. But what these guidelines should state that very often the most expensive camcorder, can not be the best for a particular application. Understand which features are most useful for your application, considering the price range camera.
Conclusion
Technological improvements in CCD and CMOS image sensors and the introduction of new high-definition display andThe recording formats have led to the introduction of many models of digital cameras. The valuation guidelines were made available on the camcorder for use in surveillance applications.
To monitor the quality of the optical images is of the utmost importance. Camcorder resolution and sensitivity are the main factors to consider, with a variety of factors such as image and the pixel field of view, the pixel size and frame rate , image stabilization,Alternative lens and interchangeable lens options, integrated mode, digital zoom, resolution, user interface, video formats, storage media, manual gain, the infrared mode, video compression, external audio inputs, viewfinder, robustness and compression video.
Although this decision are the guidelines helpful in understanding the important camera specifications before buying this camcorder, you should, and you do your own research of models available,Based on these guidelines, you can choose which model to get the best performance, and conduct its own tests in real situations. You can learn that other factors may be important for your specific application and the final decision is a compromise between these other factors.
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