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April 14th, 2010 admin No comments

Which camcorder is best for surveillance?

To See all graphics / charts / illustrations referred to in this article, click here.

A bstract

Looking for a digital camcorder for use in conducting surveillance? Well, technological improvements in CCD and CMOS image sensors and the introduction of new high-definition display and recording formats have certainly led to the introduction of many different digital camcorder models. Due to the large variation in the features and price points, it's more difficult than once to select the best digital camcorder. Certainly, some models better than others in dealing with the specific application for which the camcorder is used and the functions required. Because there are so many factors involved in making a selection and since de new models are often introduced, it is most useful for guidance in the assessment of models intended for a specific application to. Then, as new models become available, they can be compared with existing models based on the same guidelines.

The purpose of this paper is to provide guidelines that should be considered when assessing camcorders for use in surveillance applications. These applications are those that would be used by military, law enforcement personnel and special investigative techniques for gathering evidence or conducting Electronic News Gathering and usually contain a remotely. Although these are useful guidelines for understanding major camcorder specs prior to making your camcorder purchase decision, we suggest your own research to review the available models and based on these guidelines, select the models that are expected to take the best performance and your own testing under real-life situations to perform. You can learn that other factors may be important to your specific application and that your final decision is a compromise of the other factors.

Monitoring, optical image quality is of paramount importance. Camcorder resolution and sensitivity are key factors to consider, with a variety of factors including image and pixel-field-of-view, the pixel size and the frame rate, image stabilization, alternative lens options and interchangeable lenses, integration mode, digital zoom and resolution, user interface, video formats, recording media, Manual Gain infrared mode, video compression, external audio inputs, viewfinder, robustness, and video compression.

Camcorder Resolution

Video resolution is influenced by a variety of different camcorder specifications. It is known that the high-definition Camcorders higher resolution than standard definition formats deliver. It is important to realize that if the camcorder is used to image sequences later register must be considered (instead of just using the camcorder to the video output in real-time view), both the optical resolution and the recording format should be viewed when determining the ultimate resolution video. individually, the optical resolution is not only dependent on the detector array size, but also the image pixel and field-of-view. Soak HD format also affects resolution. Finally, there are other factors that account resolution, the ultimate camcorder to adopt a resolution which may give rise.

Detector Array Size:

It seems that any camcorder a slightly different imaging detector. While recording in HD format can be 1280x720, 1440x1080, or 1920x1080, graphic detectors can vary quite a bit. As shown in the table for a selection of mid-range camcorders, detector array sizes ranging from single chip cameras arrays as large as 1920x1080 (Canon HF-10 and Sony HDRSR11) to three-chip blocks of detectors as large as 1440x1080. The physical size of the image detector also varies from camcorder to camcorder.

Image and Pixel Field of View:

As shown in the accompanying chart (Reference link above) the combination the physical size of the image of the camcorder detector (eg 1 / 3 ") and the focal length of objective lens (50mm for example) result in an image field-of-view (FOV), defined as the angle from which image information is received. There are separate angles corresponding to the horizontal and vertical directions, depending the aspect ratio of the image. For widescreen video formats, the vertical FOV is 9 / 16 of the horizontal FOV. All camcorders have zoom lenses where the focal length varies from one Wide mode (with the largest angular FOV) to a telephoto position (with the smallest angle FOV). A smaller field-of-view results in a higher image magnification that would be required for small objects at a distance view.

Smaller imaging detectors to create smaller corners of the eye using the same lens with a focal range. For example, a 50 mm lens provide a horizontal FOV of 5.5 ° and 3.7 °, when used in combination with a 1 / 2 "and 1 / 3" format detector, respectively. Based on the variation the detector size and lens focal lengths, the angular field of view of different camcorders vary accordingly. The image FOV can be determined for any camcorder on the basis of a simple formula.

The pixel FOV (also known as the instantaneous field of view or IFOV) is a measure of the resolution of an imaging system. Although related, FOV and image pixel FOV are distinct and a camcorder with the narrow FOV image does not necessarily have a narrow FOV corresponding pixel. As shown in the table (reference to the link above) while the Canon camcorders are the smallest FOV and image pixel values, the Sony HDR-SR11 has a smaller pixel FOV, FOV despite an image that is nearly twice as wide as that of Canon.

A handy FOV calculator can be used to determine the camcorders FOV values for certain candidates. Pixel FOV is calculated as its detection, identification and recognition gamma values for certain sizes specified object at a certain distance.

Format:

The difference between HD recording formats is beyond the scope of this Paper. However, the impact of The recording format of resolution is critical to imaging performance for surveillance applications and is described here.

If the figure (referenced in the first link Article), standard definition camcorders (with an aspect ratio of 4:3) recorded video with 480 horizontal lines per frame resolution of 640 x 480. (This is for NTSC format. PAL recorded with 576 rows per frame giving a resolution of 640x576). Widescreen versions of this standard definition camcorder with a 16:9 ratio are also available and included with something higher resolution of 720 x 480 (720x576 for PAL versions). Because of the limitations of the recording format, it would not have been useful to have a high resolution CCD / CMOS detector greater than 720x480 pixels in NTSC standard definition camcorder, except under certain conditions (such as zooming in on the central pixels to see). However, with the introduction of higher resolution recording formats, higher resolution detectors sense.

Camcorder Sensitivity

High definition refers to the video with a higher resolution than most standard definition and refers to resolutions on the basis of either 720 lines / frame or 1080 lines / frame. Recording Formats can either 1920x1080, 1440x1080 and 1280x720. Consequently, available with 720 or 1080 lines per frame recording formats with a resolution of 1280x720 and 1920x1080, respectively. It is important to understand the recording format for any camcorder into account. If the full resolution of the sensor is necessary to perform the supervisory function, and make sure that the camcorder records in sufficient resolution.

Was this white paper is about digital cameras, the above discussion of the recording format was sufficient to describe the effects on image quality. However, since motion video contains, the fact that some camcorders "interlaced" video recording, while other "progressive" video has some relevance, particularly when motion is important to the nature of supervision is carried out. If not, then the relevance of interlace vs. progressive scan is less important.

Other Resolution factors:

It is noteworthy that in those camcorders that use of three sensors, Pixel Shift technology operates in the horizontal shaft incremental improvements to the sensor resolution using interpolation. This complicates the calculation of the optical resolution somewhat, but not a primary factor.

Camcorder low light sensitivity is usually of primary interest for surveillance applications, especially when imaging at dusk or dawn, but also to confirm of a night vision module that intensifies ambient light. The guidelines for camcorder review are listed below. We recommend a review of the following factors: the recommended Minimum Illumination Specification, Objective Lens F-number, detector pixel size, Night Vision Module availability.

As such, but criteria for the comparison of these including: lens F-number, pixel size, electronic noise, it is clear that the low-light performance, as mentioned on the list of camcorders specifications because different cameras can produce varying results, even though the specifications may be similar.

Therefore, once you have identified a few camcorders that several characteristics of interest and the performance you need, it is important to test the camcorder's low light capabilities.

Recommended Minimum illumination Specification:

Very often, low-light performance specifications provided on the specification of a camcorder recorded. These are usually described as "low-light sensitivity" or "minimal lighting" and the result is expressed in lux. The lower the lux rating, the better performs the camcorder in low light. However, since the details describe how those little light measurements are made is often not provided, it is extremely difficult in these figures Comparison of different camcorder models from different manufacturers to compare. (What is assumed reflectivity of the objects being viewed, what is the signal to noise ratio? Brightness of the image? etc.). As such, the use of these specifications is difficult and often unsatisfactory. Naturally, it is best to test the camcorders themselves. Some websites (As www.camcorderinfo.com) conduct their own rigorous testing.

Detector pixel Size:

Not only is the detector array size is important, but the physical size of the detector is also important for several reasons. In most cases, small physical sensor size (like 1 / 6 "format) are found in less expensive camcorders, while larger detectors (eg 1 / 3 "format) can be found in high performance camcorders. Physically small detectors smaller, less expensive lenses and result in a compact, lower cost camcorders. For surveillance applications, an important consideration is that the sensitivity to light decreases with pixel size. While larger pixels in generally more light sensitivity and his superior in the overall picture in low light or at night, larger pixels also result in a decrease in resolution (in the treatment of a particular focal length lens). Even larger pixels with large array sizes result in large arrays and large lenses. So, smaller pixels are often preferable. One must compare the sensitivity of camcorders with the smallest pixels with other camcorders are considered. Pixel sizes for a variety of digital camcorders are shown in the accompanying graph (referenced in the first link in the article).

Objective Lens F-number:

As with SLR cameras, lens F-number is extremely important for a camcorder low sensitivity. All other things being equal, a lens with a low f-number (eg F1.4) focuses a large part of the light from the scene on the sensitivity of the camcorder's imaging detector. A lens with an F number that is twice as high (F2.8), only 25% of light to pass through it, making the camcorder 25% as sensitive. That's a lot! For compact camcorders with built-in lenses, sometimes the lens must be designed with a relatively high F-number for the compact design still retained to provide the desired zoom range. In particular, one sees that the F-number at the longer focal length values increased slightly. F-number at the maximum zoom setting for a variety of digital camcorders are shown in the diagram.

Night Vision Module Availability:

For camcorders are used for surveillance applications, the availability of a nocturnal vision module is very important, particularly for imaging at a distance and at night. Camcorders simply do not have sufficient sensitivity to light perception in these environments possible. However, by awarding a night vision module as here be mentioned, light sensitivity of the camcorder can be increased by up to ten F-stops. As is known, the resulting images will be green night vision, lack of all color. But, can expect reasonable image is produced in Starlight and moonlight. Some of these modules can see in the dark to see by clicking the link above.

Other factors to consider

In assessing the camcorder for surveillance applications, resolution and sensitivity are usually the most important considerations, Other factors may deserve attention. Some of these are listed below.

Media: "Media" refers to the place where the video is saved. Many camcorders use different media types. The following are the most common forms of media and a number of considerations for surveillance applications:

MiniDV tape - These are used for many years. The disadvantage is the need to fast forward and rewind instead of direct access. They are known as very reliable, they are widely available and robust. Moreover, it is often useful to physical media with surveillance images have a soft copy only one who could more easily be misplaced or mislabeled.

MiniDVD - Although a trusted media is not as easy as one might expect since the DVD can often not be incorporated into DVD players. Also, recording the highest quality may result significantly lower capacity.

Hard Disk Drive (HDD) - These are generally a high-capacity media (eg 120 GB) with a long record times. Backup is obviously important and necessary. Also note carefully as compressed video is used for storage in the available capacity.

Flash memory - Flash memory (such as solid state memory and memory card) is very attractive because there are no moving parts results in a compact and efficient design. Capacities are increasing each year.

Image stabilization:

Image stabilization is a feature that allows the camcorder image improve during the hand-held video recordings, reduce blur caused by motion camcorder. The stabilizer corrects camcorder shake instantly, so that the hand-held shots at full telephoto (such as video taken from a moving car) are smooth and stable. This image stabilizers can be either optical or digital in design. Optical image manipulation stabilizers usually a prism into the lens to the image projected on the camcorder detector to stabilize. Digital image stabilizer usually sense the motion camcorder and uses additional rows and columns at the edge of the detector, a shift of the image an appropriate amount for certain types of motion stabilization. Normally, the optical image stabilizers, but more expensive, are preferable because they better remove the component of the motion blur.

Interchangeable lenses:

Many lower cost camcorders have non-removable lenses. These lenses are compact and highly integrated into the body of the camcorder, have a very large zoom range and even macro capability. Normally, the field-of-view of the integrated zoom lens selected for the desired FOV range for most applications a reality. However, for greater versatility, higher-end camcorders offer a removable lens and a lens mount so that a series of lenses can be offered to a wider variety of applications, including a wider angle and longer distance view. (See a list of mid-range camcorder with removable lenses here). For non-interchangeable lens camcorders, if wider angle or more telephoto FOV values are required, sometimes Adapters offered to enhance the desired change. But the result is a reduction in optical quality. In monitoring videographer, interchangeable lenses, a major advantage as the magnification offered by fixed lens camcorders is not enough for the desired application. Furthermore, night vision modules designed for interchangeable lens camcorders fit between the lens and the camcorder and keep everything objective 'features including motorized zoom, image stabilization and auto-iris.

Digital zoom:

Digital zoom is an important feature for any camcorder. Because it is not possible for all imaging detector resolution can enjoy the camcorder's viewfinder or display digital zoom enables the operator to see details on the viewfinder that would otherwise go unnoticed until digital images were later analyzed. Moreover, it is useful to note that a larger pixel detector array allows the operator to carry out more than a digital zoom camcorder with a smaller detector without the effects of pixelization.

User Interface:

Each camcorder operator will confirm that the accessibility features of some importance. Drill down through sub-menu after sub menu to access get routine functions is not desirable to do while in the field.

IR mode:

Some camcorders have a sensitivity for which near infrared light using an infrared illuminator to brighten scenes. For a variety of reasons, these illuminators are not applicable to many monitoring situations. For one thing, the illuminators normally included with the camcorder is not sufficient lighting project at the distances of interest. Moreover, they can be detected by others with most camcorders and CCD cameras.

Manual Gain:

For low-light situations, some camcorders manual mode to get the user to manually adjust the gain in the video image permits to offer, usually rises to 18 dB. Though grainy, for monitoring applications, video normally a significant improvement over non-acquired or acquired auto versions.

Shutter:

If enforcement of the standard frame rate (eg 60Hz) is not necessary because the objects are not supervised by moving quickly, the frame rate and shutter speed detector to be reduced (for example, 1 / 3 sec) so that each of the pixels of the sensor light integrating over a longer time they are exposed. In dark environments, selecting the longest acceptable integration time may be sufficient to create a usable image in the dusk or dawn.

External audio inputs:

To prevent sounds like the appearance of a pure optical geek, it is important to note that the audio quality and access to external audio inputs is important for monitoring videographer. The built-in microphone not always work when shooting images of far away or if you just need to filter out directional ambient noise.

Viewfinder:

When conducting secret surveillance, with a viewfinder of the camcorder is sometimes important to avoid the bright lights of the LCD.

Robustness:

Another serious compromise is the lack of robustness in the camera hardware - the thin switches and controls that enable videographers stress. If you are in the field below potentially hazardous conditions, you do not want to play with few controls and LCD panels that are easy to come apart.

Price:

Of course, the price is always a consideration in evaluating the many, many camcorder models available today. But, what these guidelines should prove is that very often the most expensive camcorder is not the best for a specifi c application. Understand what features are most beneficial to your application in respect of a camcorder price.

Conclusion

Technological improvements in CCD and CMOS image sensors and the introduction of new high-definition playback and recording formats have led to the introduction of many different digital camcorder models. Guidelines are provided in the assessment for use in camcorders surveillance applications.

Monitoring, optical image quality is of paramount interest. Camcorder resolution and sensitivity are key factors to consider, with a variety of factors such as image and pixel-field-of-view, the pixel size and the frame rate, image stabilization, alternative lens options and interchangeable lenses, integration mode, digital zoom and the resolution, user interface, video formats, media, Manual Gain infrared mode, video compression, external audio inputs, viewfinder, robustness, and video compression.

Although these helpful guidelines for understanding major specs camcorder, prior to making your camcorder purchase decision, we recommend that you carry out your own research of available models and based on these guidelines, select the models are expected to provide the best performance and testing your own real-life situations to perform. You can learn that other factors may be important for your specific application and that your final decision is a compromise of these other factors.

DISCLAIMER: We have taken every effort to provide accurate information. However, may We accept no liability for errors or inaccuracies. If you identify errors or need assistance, please contact us. Thank you.

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