Which Camcorder is Best For Surveillance?

2010 January 24

by Rick

Abstract

Looking for a digital camcorder for use in performing scrutiny? Well, equipment improvements in CCD and CMOS image sensors as well as the introduction of new high classification show and recording formats have surely resulted in the introduction of lots of uncommon digital camcorder models. Since of the wide alteration in facial advent and price points, it's more trying than ever to select the optimal digital camcorder. Surely, some models will be better than others in consideration of the point application for which the camcorder is intended and the facial advent that are vital. Since there are so many factors involved in making a choice and since new models are often introduced, it's best to grant guidelines useful when evaluating models intended for a point application. Then, as new models become available, they can be compared to existing models based on the same guidelines.

The goal of this paper is to grant guidelines that should be considered when evaluating camcorders for use in scrutiny applications. These applications are those that would be used by services, law enforcement and special analytical personnel for gathering prove or performing electronic news gathering and usually include viewing at a distance. While these are useful guidelines for understanding vital camcorder specs, prior to making your own camcorder buy choice, we recommend that you perform your own research of available models and, based on these guidelines, select those models that are probable to give up the best routine and perform your own tests under real-life situations. You may learn that other factors may be vital to your point application and that your final choice is a negotiate of those other factors.

For scrutiny, optical image feature is of peak substance. Camcorder resolution and sensitivity are the primary factors to consider, with a diversity of related factors such as image and pixel fields-of-view, the pixel size, as well as the frame rate, image stabilization, alternative lens options and lens interchangeability, integration mode, digital zoom and show 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 unnatural by a diversity of uncommon camcorder specifications. It is well known that high classification camcorders give up higher resolution than standard classification formats. But, it is vital to grasp that if the camcorder is used to record image sequences that are later to be viewed (rather than using the camcorder just to view the video output in real time), both the optical resolution and the recording format must be considered in determining the ultimate video resolution. Considered unconnectedly, the optical resolution depends not only on the detector array size but also the image and pixel field-of-view. HD recording format also affects resolution. Finally, there are other resolution factors that may warrant consideration in order to establish the ultimate camcorder resolution.

Detector Array Size:

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

Image and Pixel Field-of-View:

As shown in the accompanying chart (allusion at link below) the combination of the physical size of the camcorder's imaging detector (for example 1/3") and the focal length of its objective lens (for example 50mm) result in an image field-of-view (FOV) that is defined as the angle of view from which image information is expected. There are break angles corresponding to the horizontal and vertical directions depending on the aspect ratio of the image. For wide screen video formats, the vertical FOV is 9/16 of the horizontal FOV. All camcorders have zoom lenses where the focal length varies from a wide angle spot (with the largest angular FOV) to a telephoto spot (with the smallest angular FOV). A smaller field-of-view results in a higher image magnification as would be vital to view small stuff at a distance.

Smaller imaging detectors make narrower angles of view when used on the same focal length lens. For example, a 50 mm lens delivers a horizontal FOV of 5.5 and 3.7 when used with a 1/2" and 1/3" format detector, respectively. Based on the alteration of detector sizes and lens focal lengths, the angular field of view for uncommon camcorders varies accordingly. The image FOV 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 the resolution of an imaging system. Though related, image FOV and pixel FOV are evident and a camcorder having the narrow image FOV does not automatically have a corresponding narrow pixel FOV. As shown in the table (allusion at link below), while the Canon camcorders have the smallest image and pixel FOV values, the Sony HDR-SR11 has a small pixel FOV despite an image FOV that is nearly twice as wide as those for Canon.

A handy FOV calculator can be used to establish the FOV values for particular candidate camcorders. Pixel FOV is also calculated as are detection, identification and recognition range values for particular party object sizes at a party distance.

Recording Format:

The variation linking the uncommon HD recording formats is beyond the scope of this white paper. But, the impact of recording format on resolution is critical to imaging routine for scrutiny applications and is described here.

As shown in the figure (allusion at the link below), standard classification camcorders (with a 4:3 aspect ratio) recorded video with 480 horizontal rows per frame giving a resolution of 640 x 480. (This is for NTSC formats. PAL formats recorded with 576 rows per frame giving a resolution of 640x576). Wide screen versions of these standard classification camcorders with a 16:9 aspect ratio were also available and recorded with slightly larger resolution of 720 x 480 (720x576 for PAL versions). Since of the limitations of the recording format, it would not have been useful to have a high resolution CCD/CMOS detector larger than 720x480 pixels in a standard classification NTSC camcorder except under particular circumstances (like zooming in to view inner pixels). But, with the introduction of higher resolution recording formats, higher resolution detectors make sense.

Camcorder Sensitivity

High classification refers to video having higher resolution than standard classification and most frequently refers to resolutions based on either 720 rows/frame or 1080 rows/frame. Recording formats can either be 1920x1080, 1440x1080 and 1280x720. Consequently, are available with either 720 or 1080 rows per frame recording formats having a resolution of 1280x720 and 1920x1080 respectively. It is vital to be with you the recording format for any camcorder under consideration. If the full sensor resolution is necessary to perform the scrutiny gathering, then make sure that the camcorder records in ample resolution.

Had this whitepaper been about digital still cameras, the above conversation of recording format would've been ample to give reasons for the effects on image feature. But, since video incorporates motion, the fact that some camcorders record "interlaced" video while others record "progressive" video has some weight, above all when motion is vital to the type of scrutiny being performed. If not, then the weight of interlace vs. progressive scan is less vital.

Other Resolution Factors:

It's worth mentioning that in those camcorders that use three sensors, pixel shift equipment has been employed in the horizontal axis to make incremental improvements to the sensor resolution by using interpolation. This complicates the estimate of optical resolution to some extent, but may not be a primary factor.

Camcorder low-light sensitivity is usually of primary substance for scrutiny applications, above all when imaging at dusk or dawn, but also when attaching a night vision module that intensifies ambient light. The guidelines for camcorder evaluation are listed below. We recommend a review of the later factors: the Recommended Smallest Illumination Specification, Objective Lens F-number, Detector Pixel Size, Night Vision Module availability.

As such, but criteria enabling the comparison of these counting: objective lens F-number, pixel size, electronic noise reduction, It is apparent that low-light routine as meticulous on the list of the camcorders specifications since uncommon cameras can produce varying results, even though the specifications may be similar.

Consequently, once you've identified a few uncommon camcorders that have the facial advent of appeal and the routine that you require, it is vital to test the camcorder's low-light capabilities.

Recommended Smallest Illumination Specification:

Quite often, low-light routine specifications are provided on a camcorder's specification sheet. These are usually described as either "low light sensitivity" or "smallest illumination" and the result is given in lux. The lower the lux rating, the better the camcorder performs in low light. But, since the details describing how these low-light measurements are made is not often provided, it is exceptionally trying to compare these figures when comparing uncommon camcorder models from uncommon manufacturers. (What's the assumed reflectivity of the stuff being viewed? What's the signal-to-noise ratio? Image brightness? etc.). As such, use of these specifications is intricate and not often satisfying. It is obviously best to test the camcorders yourself. Some websites (such as camcorderinfo.com) perform their own very rigorous tests.

Detector Pixel Size:

Not only is the detector array size vital, but the physical size of the detector is also vital for a number of reasons. Most often, small detector physical sizes (such as 1/6" format) are found in less pricey camcorders while larger detectors (e.g. 1/3" format) are found in higher routine camcorders. Physically small detectors require small, less pricey lenses and result in compact, lower cost camcorders. For scrutiny applications, an vital consideration is that light sensitivity decreases with pixel size. While larger pixels in general have more light sensitivity and are superior when imaging in low light or at night, larger pixels also result in a decrease in resolution (in consideration of a fastidious focal length lens). Also, larger pixels with large array sizes result in large arrays and large lenses. So, smaller pixels are often preferable. One should compare the sensitivity of camcorders with the smallest pixels with other camcorders being considered. Pixel sizes for a diversity of digital camcorders are shown in the accompanying chart (allusion at link below).

Objective Lens F-Number:

As with SLR cameras, lens F-number is exceptionally vital to a camcorder's low light sensitivity. All other things being equal, a lens with a low f-number (such as F1.4) focuses much of the light from the scene onto the camcorder's sensitive imaging detector. A lens with an F-number that is twice as high (F2.8) will pass only 25% of the light owing to it, making the camcorder 25% as sensitive. That's a lot! For compact camcorders with integral lenses, sometimes the objective lens must be designed with a moderately high F-number in order to retain the compact design yet give up the desirable zoom range. In fastidious, one finds that the F-number at the longer focal length values increases slightly. F-numbers at the maximum zoom background for a diversity of digital camcorders are shown in the accompanying chart (allusion at link below).

Night Vision Module Availability:

For camcorders to be used for scrutiny applications, the availability of a night vision module can be quite vital, above all for imaging at a distance and at night. Camcorders simply do not have ample light sensitivity to enable imaging in these environments. But, by attaching a night vision module such as those shown on our site at http://www.electrophysics.com/night-vision, the light sensitivity of the camcorder can be increased by up to ten F-stops. As is well known, the ensuing night vision images will be green, absent of all color. But, evenhanded images can be bent in starlight and moonlight. Some of these night vision modules can be seen by clicking on the link below.

Other Factors To Consider

In evaluating camcorders for scrutiny applications, resolution and sensitivity are usually the primary considerations, other factors may deserve attention. Some of these are listed below.

Media: "Media" refers to where the video will be stored. Many camcorders use several uncommon media types. The later are the common types of media and some considerations for scrutiny applications:

MiniDV Tape - These have been used for many years. The downside is the need to quick forwards and rewind rather than direct access. But, they are known to be quite reliable, they are widely available and rugged. In addition, it is often convenient to have physical media with scrutiny footage rather than a soft copy only which could more easily be misplaced or mislabeled.
MiniDVD - Though a familiar media, it may not be as convenient as one expects since the DVD often cannot be directly inserted into DVD players. Also, recording in the peak feature sometimes results in significantly lower room.
Hard Disk Drive (HDD) - These are generally high room media (e.g. 120 gigabytes) with long record times. Backup is obviously vital and necessary. Also note carefully if compressed video is being used for storage in order to increase the available room.
Flash Memory - Flash memory (such as solid state memory and memory cards) is very attractive since there are no moving parts ensuing in a compact and efficient design. Capacities are increasing every year.

Image stabilization:

Image stabilization is a camcorder feature that helps improve image feature during hand-held video recordings, reducing blur due to camcorder motion. The stabilizer instantly corrects camcorder shake so that hand held shots at full telephoto (such as video taken from a moving car) are smooth and steady. These image stabilizers can be either optical or digital in design. Optical image stabilizers usually manipulate a prism in the lens to stabilize the image when projected on the camcorder detector. Digital image stabilizers usually sense the camcorder motion and, taking advantage of extra rows and columns on the perimeter of the detector, shift the image an appropriate amount to stabilize particular types of motion. Naturally, the optical image stabilizers, though more pricey, are preferable since they better remove the blur component of the motion.

Lens interchangeability:

Many lower cost camcorders have non-comes off objective lenses. These lenses are compact and highly integrated into the camcorder's housing, have a very wide zoom range and even macro capability. Naturally, the field-of-view of the integrated zoom lens is selected to achieve the FOV range desired for most applications. But, for increased versatility, higher-end camcorders offer a comes off lens and a lens mount so that a series of lenses can be existing for a wider alteration of applications, counting wider angle and more telephoto viewing. (See a list of mid-range camcorders having comes off lenses here). For non-comes off lens camcorders, if wider angle or more telephoto FOV values are vital, adapters are sometimes existing to change the magnification as desired. But the result is a reduction in optical feature. For the scrutiny videographer, like peas in a pod lenses can be a fantastic benefit if the magnification existing by fixed lens camcorders isn't ample for the desired application. In addition, night vision modules that are designed for comes off lens camcorders fit linking the lens and camcorder and retain all that objective lens' functions counting motorized zoom, auto-iris and image stabilization.

Digital zoom:

Digital zoom is an vital feature for any camcorder. Since it is not possible to appreciate all the imaging detector's resolution on the camcorder's viewfinder or show panel, digital zoom enables the operator to view details on the viewfinder that would otherwise go unnoticed until digital images were later analyzed. In addition, it's useful to note that a detector having a larger pixel array enables the operator to perform more digital zoom than with a camcorder having a smaller detector without the effects of pixelization.

User interface:

Any camcorder operator will confirm that accessibility to facial advent is of some substance. Drilling down owing to sub-menu after sub-menu to access routine functions is not a desirable thing to do while in the field.

Infrared mode:

Some camcorders feature a sensitivity to near infrared light permitting the use of an infrared illuminator to brighten scenes. For a diversity of reasons, these illuminators are not applicable for many scrutiny situations. For one thing, naturally the illuminators included with the camcorders do not project ample illumination at the distances of appeal. In addition, they can be detected by others with most camcorders and CCD cameras.

Manual Gain:

For low-light situations, some camcorders offer a manual gain mode that permits the user to manually adjust the gain in the video image, usually increases up to +18dB. Though grainy, for scrutiny applications, the video images are naturally a significant improvement over non-gained or even auto-gained versions.

Shutter Speed:

If maintaining the standard frame rate (for example 60Hz) is not necessary since the stuff under routine are not moving promptly, the frame rate and detector shutter speed can be cut-rate (for example to 1/3 sec) so that each of the sensor's pixels will integrate light over a longer time that they are exposed. In darkened environments, selecting the highest acceptable integration time may be ample to grant a usable image at dusk or dawn.

External Audio inputs:

In order to disqualify the advent of sounding like a pure optics geek, it is vital to mention that audio feature and access to external audio inputs is vital for the scrutiny videographer. The built-in microphone doesn't always work well when shooting images far away or when you need a touch more directional to filter out ambient noise.

Viewfinder:

When performing covert scrutiny, having a viewfinder on the camcorder is sometimes vital in order to disqualify the illumination from the bright LCD panel.

Robustness:

Another serious negotiate is the lack of robustness in camera hardware - the flimsy switches and reins that cause videographers stress. When you're out in the field under maybe perilous situation, you don't want to be before a live consultation around with small reins and LCD panels that easily come apart.

Price:

Of course, price is always a consideration when evaluating the many many camcorders models available today. But, what these guidelines should show is that very often, the most pricey camcorder may not be the best for a point application. Be with you what facial advent are most beneficial for your application in consideration of camcorder price range.

End

Equipment improvements in CCD and CMOS image sensors as well as the introduction of new high classification show and recording formats have resulted in the introduction of lots of uncommon digital camcorder models. Guidelines have been provided when evaluating camcorders for use in scrutiny applications.

While these are useful guidelines for understanding vital camcorder specs, prior to making your own camcorder buy choice, we recommend that you perform your own research of available models and, based on these guidelines, select those models that are probable to give up the best routine and perform your own tests under real-life situations. You may learn that other factors may be vital to your point application and that your final choice is a negotiate of those other factors.

To View all figures and illustrations referenced in this article, CLICK HERE

DISCLAIMER: We have made every attempt to grant right information. But, we cannot accept any responsibility for errors or inaccuracies. Should you identify errors or require help, please contact us directly. Thank you.

Author: Josh L. White
Article Source: EzineArticles.com