Viewing angle of the CCTV camera lens. Dependence of the viewing angle on the focal length of the video camera lens. This can be represented more clearly in this way
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All devices are connected via USB 2.0 and do not require additional installation. There are additional software modules StreamEngine and CamEngine that support third-party software (Streamlabs OBS, OBS, XSplit). StreamEngine relieves the computer load by hardware encoding H.264 and CamEngine contains advanced features artificial intelligence. Thanks to it, you will have access to beauty filters, color correction, and sticker masks.
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MSI GF63 Compact and Affordable Gaming Laptop
For those who are looking for an inexpensive and compact laptop for study and entertainment, the MSI product range includes the GF63 model. This gaming laptop is one of the affordable ones, but also has a modern and stylish design.
Thanks to the thin bezels of the MSI GF63 screen, it is noticeably more compact than similar solutions in the “traditional” format, and the strict design without overly aggressive elements will not distract from study and work. To connect a gaming monitor or a projector for presentations, the laptop has an HDMI port conveniently located on the back, and on the sides there are various connectors for gaming peripherals and office equipment. A separate advantage of the laptop was the unusual gaming devices autonomy - up to 7 hours.
MSI GF63 is equipped with a high-quality Full HD IPS screen with a diagonal of 15.6 inches. The device features wide viewing angles vertically and horizontally, natural color reproduction and a matte surface that does not turn into a mirror in bright light.
Responsible for gaming performance in a laptop powerful processor Intel Core i5-8300H or Core i7-8750H, comparable to desktop solutions, and video card GeForce GTX 1050 or GTX 1050Ti. The laptop is capable of delivering a stable 60 frames per second in most popular online games, including the dynamic tactical online shooter Warface, which seamlessly combines matches against other players with PvE and cooperative modes.
When purchasing an MSI GF63 in the DNS store chain, there are several promotions: interest-free installments for two years 0-0-24, increased cashback with points and valuable codes for rare bonus weapons in Warface.
The cost of MSI GF63 is 62,999 rubles.
MSI PS63 Modern - a stylish laptop with up to 16 hours of battery life
MSI is primarily known as one of the oldest manufacturers of gaming laptops, but recently the company has been actively expanding its presence in the segment of devices for business and creative tasks. The MSI PS63 Modern model is a balanced, universal laptop with decent performance and a strict but original exterior that is suitable for both students and accomplished professionals.
The 15-inch laptop weighs only 1.6 kg, but is equipped with a capacious battery that can provide up to 16 hours battery life. The case is made of durable aluminum alloy and is certified according to the MIL-STD 810G standard adopted by the US armed forces - the laptop is protected from vibrations, shaking, temperature and pressure changes, you can safely take it with you on a business trip, a photo expedition, or just carry it everywhere with you. with you in your backpack.
Despite being only 1.6 cm thick when closed, the MSI PS63 Modern is equipped with a rich selection of connectors: 3 standard high-speed USB 3.1, USB Type-C with DisplayPort image output, full-size HDMI and a card slot microSD memory. At the same time, the laptop supports the standard fast charging Qualcomm Quick Charge 3.0 and is able to quickly replenish the charge of mobile devices connected to it.
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The price of MSI PS63 Modern is 127,999 rubles.
The Samsung Space Gaming Monitor gaming panel can be pressed against the wall
Samsung Company presented at the gamescom 2019 exhibition, which takes place in Cologne (Germany), an interesting monitor - a gaming-grade panel Space Gaming Monitor (model SR75Q).
The new product inherited the concept from monitors. main feature These devices consist of an unusual stand, with which the device is attached to the edge of the table. When not in use, the panel is literally pressed against the wall. During operation, the user can move the screen towards him and tilt it at the desired angle.
The presented Space Gaming Monitor measures 32 inches diagonally. The resolution is 2560 × 1440 pixels, which corresponds to the QHD format. The panel boasts narrow bezels on three sides.
Technology implemented AMD Radeon FreeSync, which improves the smoothness of the image during games. The refresh rate reaches 144 Hz.
The HDMI cable and power cable are made in the form of a combined Y-type cable, which is hidden inside the stand. This allows you to give your workspace a neat look.
Nothing has been announced yet about the price and start date of sales of the new product.
Samsung CRG5 gaming monitor with 240 Hz refresh rate goes on sale in Russia
Gaming curved Samsung monitor CRG5 (C27RG50FQI) with a diagonal of 27 inches is now available for purchase in Russia. New product from the South Korean technology giant can provide smooth images High Quality during the game.
The display has no frames on three sides, and the panel bending radius is 1500R. The new product is housed in a stylish black and blue case. It uses a curved flicker-free VA panel that supports refresh rates up to 240 Hz and a response time of 4 ms. High refresh rate is one of the main features of the CRG5 monitor, which was achieved through the use of G-Sync Compatible technology. Due to this, users get smoother images in games.
The display supports a resolution of 1920 × 1080 pixels, and the contrast level reaches 3000:1. The new product provides accurate color reproduction with deep dark and bright white shades. The viewing angle vertically and horizontally is 178°, and the brightness reaches 300 cd/m².
The CRG5 is equipped with two HDMI interface, one DisplayPort 1.2, as well as a headphone jack. In addition, for games of different genres, the developers have prepared settings presets that include parameters such as gamma, contrast, clarity and color.
Already, the Samsung CRG5 gaming monitor is available in the company’s company stores, as well as in partner networks at a recommended price of 24,990 rubles.
ASUS ROG Strix XG17: portable gaming monitor with tripod
In May, at Computex 2019, ASUS sampled the ROG Strix XG17 portable monitor, designed for gaming. Now this device has been officially presented: the announcement took place at the Gamescom 2019 event.
Let us remind you that the ROG Strix XG17 monitor is equipped with a 17.3-inch IPS display with a resolution of 1920 × 1080 pixels (Full HD), a refresh rate of 240 Hz and a response time of 3 ms.
The built-in battery provides up to three hours of battery life. Quick Charge 3.0 fast charging technology has been implemented.
As part of a presentation at Gamescom 2019, new details about the panel were revealed. In particular, it is reported that adaptive synchronization Adaptive-Sync has been implemented, operating in the frequency range from 48 to 240 Hz: this allows you to get a smooth image with mid-range video cards.
The portable monitor comes with a ROG tripod, which allows you to position the device at different heights and angles. For example, a monitor can be installed directly above a gaming laptop and extend the screen space onto it. The ROG tripod is also useful when using the monitor with consoles and mobile gadgets.
A special feature of the panels is their support for DSC video stream compression technology, which is a generally accepted standard. It serves to transmit video content in UHD format over a single cable without significant loss in picture quality, and with support for variable screen refresh rate and extended dynamic range.
With DSC, the new monitors are capable of delivering detailed 4K/UHD resolution images at 144Hz refresh rates over a single DisplayPort 1.4 connection, without the need for chroma subsampling that could negatively impact color accuracy.
The ROG Strix XG43UQ model measures 43 inches diagonally. The panel complies with the DisplayHDR 1000 standard. AMD Radeon FreeSync 2 HDR technology is mentioned, which helps improve image quality in fast-paced computer games.
The HP 22x monitor panel features a static contrast ratio of 600:1 (1000:1 typical) and a maximum brightness of 270 nits. The HP 24x, on the other hand, can offer a static contrast ratio of 700:1 (typical 1000:1) and a maximum brightness of 250 nits. In both cases, the NTSC color space coverage is 72%. Viewing angles are typical for TN panels: 170 and 160 degrees horizontally and vertically, respectively.
On the rear panel of the HP 22x monitor there is one HDMI 1.4 and D-Sub (VGA) connector, while the HP 24x has DisplayPort 1.2 instead of the latter. The stand of a larger monitor allows you to adjust its angle, height and orientation (landscape or portrait), while a more compact model can only be adjusted in tilt.
Separately, we note the support of the Omen X 27 monitor for AMD FreeSync 2 HDR technology, which is responsible not only for frame synchronization and elimination of image tearing, but also provides image output with enhanced dynamic range(HDR). Interestingly, the regular Omen 27 supports competing technology NVIDIA G-Sync and is not capable of outputting an HDR image.
The set of video connectors on the rear panel includes two HDMI 2.0 ports and one DisplayPort 1.4. Through the latter, the image is output at a frequency of 240 Hz. HP also equipped the Omen X 27 with a pair of USB 3.0 ports and a 3.5mm headphone jack. The monitor stand allows you to adjust its angle and height.
The HP Omen X 27 gaming monitor will go on sale next month, and its recommended price in the US will be $650 (approximately 43,500 rubles).
The curved panel of the CQ27G2 has a QHD resolution of 2560 × 1440 pixels. The other two versions correspond to the Full HD format, which indicates a resolution of 1920 × 1080 pixels.
The AOC pavilion will, of course, feature other monitors, including the 27-inch QHD flagship AGON AG273QCG. Optimized for fast-paced games, racing and shooters, the 27-inch AGON AG273QCX, AGON AG271QX and AGON AG272FCX6 models guarantee smooth, stutter-free images at frequencies from 144 to 165 Hz.
For particularly intense games, the ultra-fast AGON AG251FZ monitor, which operates at a refresh rate of 240 Hz, is suitable. Maximum immersion in the virtual world will be provided by the 35-inch curved monitor AGON AG352UCG6, equipped with G-Sync technology and WQHD display.
Dell S3220DGF: Curved Monitor with AMD Radeon FreeSync 2 HDR Support
At the annual Gamescom 2019 exhibition, Dell presented the S3220DGF monitor, designed for use as part of gaming desktop systems.
The new product is made on a curved Vertical Alignment (VA) matrix (1800R). The size is 31.5 inches diagonally, the resolution is QHD (2560 × 1440 pixels). Viewing angles horizontally and vertically - up to 178 degrees.
It is claimed that the presented panel is the world's first monitor in its category with support for AMD Radeon FreeSync 2 HDR technology and a refresh rate of up to 165 Hz.
We are talking about VESA DisplayHDR 400 certification. The brightness is 400 cd/m2, the contrast is 3000:1. Response time is 4 ms. The new product claims 92.4 percent coverage of the DCI-P3 color space and 99.7 percent coverage of the sRGB space.
The new product boasts a refresh rate of 240 Hz and a response time of 1 ms. Implemented AMD Radeon FreeSync technology to improve quality gameplay. Provides 99% coverage of the sRGB color space. The brightness is 350 cd/m2, the contrast is 1000:1.
There is AlienFX lighting. The stand provides a full range of adjustments, including switching the screen from landscape to portrait orientation.
The second new product, AW3420DW, is equipped with a 34.1-inch concave display. A WQHD matrix with a resolution of 3440 × 1440 pixels is used. Viewing angles horizontally and vertically - up to 178 degrees.
The monitor received NVIDIA G-SYNC technology. The refresh rate is 120 Hz. 98% coverage of the DCI-P3 color space and 134.5% coverage of the sRGB color space are claimed. Brightness - 350 cd/m2, contrast - 1000:1.
This model also features AlienFX lighting. The stand allows you to adjust the height, tilt and rotation of the screen.
The AW2720HF will be available on September 17th for US$600. The AW3420DW panel will become available earlier - on August 28, and its price will be $1,500.
Basic information:
As you know, LCD displays have a limited viewing angle. Image contrast strongly depends on the viewing angle of the LCD panel. At certain angles, the contrast reaches a maximum, and the image is easy to read; at others, the contrast drops sharply and reading information from the screen is very difficult. The physical dimensions of the permissible viewing angle, hereinafter referred to as the viewing angle, are determined by several factors, the main of which are the type of “liquid crystals” and power cycles. Since the viewing angle is usually smaller than desired, each LCD module acquires a reference viewing direction during its production process. Most often, the optimal viewing angle is shifted relative to the normal to the module surface.
Several types of LCD modules are offered by manufacturers with the reference direction set at different angles or positions to cover as much as possible more various applications of modules. The term “reference direction” or “offset angle” is often confused with the concept of “viewing angle”.
Definition of “displacement angle” and “viewing angle”
The offset angle is the angle between the normal to the LCD surface and the direction from which the display provides best picture and maximum contrast see Fig. 1.
This angle is determined by the display design and can be set in any direction or orientation during manufacturing. The offset angle orientation of displays is often formulated using the reference directions of a clock face. If the direction better review is above the display, they talk about the 12:00 offset or the main offset. Hantronix offers standard LCD displays with both 12:00 and 6:00 offset angle positions, and also manufactures custom modules with any offset angle.
Fig.1 Determination of viewing angle (Viewing angle)
The viewing angle is considered to be the angle formed on both sides of the offset angle within which the display contrast remains sufficiently high. Hantronix limits this contrast reduction within the viewing angle to a ratio of 1.4:1. STN digital display with 1/16 power cycle has a viewing angle of 20 degrees, and an offset angle of 25 degrees. When this display is viewed at an angle of 25 degrees above normal (as shown in Fig. 1.) it has maximum contrast and the best image. In this example the display is offset to 12:00, i.e. main type offset. When the observer's eyes are shifted relative to the display by an additional angle within 30 degrees, the contrast of the display decreases, but the image remains quite clear and easy to read. A further increase in this angle leads to a significant decrease in image quality.
Adjusting contrast and its effect on viewing angle
Adjusting the contrast voltage, VL, sets the offset angle to a specific position, but does not affect the viewing angle. A display with an offset angle of 12:00 can be optimized for an angle of 6:00 by adjusting the contrast voltage. But a 12:00 o'clock display set to the 6:00 offset position will not have the same high contrast as a 6:00 o'clock display set to the 6:00 position and vice versa.
Designers often desire LCD displays optimized for zero offset angle, where contrast is greatest when the viewer's eye falls normally on the panel.
Both 12:00 and 6:00 module types can be used for this purpose, and the contrast voltage is simply adjusted to optimize the displays at a given viewing angle.
For example, in the displays above, the viewing angle of both types of displays, 12:00 and 6:00, overlaps the perpendicular to the surface of the displays.
Procedure for adjusting contrast
Once the display offset angle has been set in accordance with its design, it can, however, be subsequently adjusted in accordance with its application. This is confirmed by the results of the development of many prototypes of products with LCD displays. For such adjustment, a potentiometer with a resistance of about 10 Kom is required, connected to the module power buses, as shown in Fig. 2, for two power supply options, single and bipolar.
The potentiometer motor is connected to the VL input of the module. The LCD is installed in a position where it is visible at the required offset angle. By adjusting the position of the potentiometer slide, and with it the voltage VL, optimal image contrast is achieved. The voltage VL can then be measured and recorded.
Subsequently, the potentiometer can be replaced in the product with a divider of two resistors, which generates the required voltage VL.
Fig.2.
Selecting the required module for the product
Most manufactured electronic products, during operation, have a certain spatial position. For desk-mounted devices, such as calculators, displays are primarily visible from above. This is usually also true for small measuring instruments. For these applications, preference should be given to 6:00 LCD modules. For products where the LCD module is located vertically, for example, on the dashboard of a car or airplane, preference should be given to 12:00 modules.
Conclusion
Choice LCD displays, in terms of viewing angle, is very important, however, the developer must keep in mind that setting the contrast is no less important, since both of these parameters jointly affect the image quality of the selected module, and ultimately the attractiveness of your design.
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The most important parameter of a video surveillance camera (even more important than resolution and sensitivity) is the viewing angle or focal length of the lens. It is this parameter that determines whether you can distinguish or identify a person at a certain distance. And it is very important to find the right compromise between the wide viewing angle of the video camera and the required image detail.
Beginners often make the mistake of thinking that if they install a camera with high resolution, then even with a wide viewing angle, it will be possible to recognize a person at a sufficient distance. However, it is not. Here's one helpful advice to select the correct focal length:
1. A person you know in the field of view of a video camera can be recognized at a distance no greater than the focal length of the video camera lens in meters. For example, a video camera with f=9 mm. will allow you to recognize a person at a distance of up to 9 m.
2. A stranger in the field of view of a video camera can be 100% identified at a distance of no more than half the focal length of the video camera lens in meters. For example, a video camera with f=9 mm. will allow you to identify a person at a distance of up to 4.5 m.
Example of an image from a video camera with different focal lengths (viewing angles)
The following tables indicate the horizontal and vertical viewing angles of video cameras depending on the size of the matrices and the focal length of the lens.
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Matrix format 1/4" |
Matrix format 1/3" |
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Matrix format 1/2.8" |
Matrix format 1/2.5" |
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Many people overlook that the size of the matrix plays no less a role in shaping the camera's viewing angle than the lens. It is interesting to note that on a video camera with a cheap 1/4 matrix and a 2.8 lens, the viewing angle will be less than on a standard 1/3 matrix and a standard 3.6 lens - 59° versus 67° horizontally!
One of the important parameters that must be taken into account before purchasing a CCTV camera is the viewing angle of the lens. This value directly determines how much of the observed area falls within the camera’s field of view. For example, to get general overview area or a cramped room, you need to choose cameras with a wide viewing angle, and if you need to focus on a specific object, choose cameras with a narrow one.
What parameters does the viewing angle depend on?
The viewing angle of the lens depends on two parameters that determine it:
- The focal length that the lens has;
- Size of the sensitive element (matrix).
It should be remembered that the larger the focal length of the lens, the smaller its viewing angle will be, therefore long-focus lenses have the ability to observe objects relatively distant from the camera, while wide-angle lenses allow you to cover a larger area of territory or room.
The dependence of the viewing angle of a video surveillance camera on the physical size of the matrix also occurs. So, the larger the matrix size, the larger the viewing angle will be, for example:
- A matrix with a diagonal of ¼ will have a viewing angle of 64° at a focal length of 2.8;
- In this case, a matrix with a ½ diagonal will have a viewing angle of 96°.
These calculations are valid for indicating the horizontal viewing angle; to find the vertical angle, it is necessary to take into account the ratio of the vertical and horizontal sides of the matrix.
Determining the required focal length
In almost all cases, there is a need to select the optimal viewing angle of the camera, which can be determined by calculating the FR of the lens. In fact, the viewing angle is dependent on the focal length. It may vary for each specific case, and directly depends on:
- Distances to the object of observation;
- Matrix size;
- The size of the observed object.
For example, a viewing angle of 100° is good for small, cramped rooms, but will be unsuitable for observing objects several tens of meters away - when viewing the recording, it will simply be impossible to distinguish the details of the object. As the focal length increases, the viewing angle narrows and it becomes possible to observe relatively distant objects.
Knowing a few and some data about the object of observation, it is not difficult to determine the necessary DF of the lens in each specific case.
The optimal FR of the lens is calculated using the formula:
F= h*S/H or F=v*S/V , Where
h – size of the horizontal side of the matrix;
S – distance to the tracking object;
H – horizontal size of the observed object;
v – size of the vertical side of the matrix;
V – vertical size of the observed object.
You can find out the size of the vertical and horizontal sides of the camera sensor from this table:
For example, let's calculate a simple problem. Given: it is necessary to observe the front side of a small garage, 4 meters wide, the distance to the object is 10 meters. The matrix size is ½ inch. Calculate a suitable DF for the camera lens. To solve, use the formula and substitute all the necessary values:
F=6.4*10/4=16
Having calculated the formula, we found that the FR of the lens should be equal to 16, but there is one more nuance. It is very important that the camera’s viewing angle is larger than calculated, otherwise nothing else will be visible except the object being observed. Therefore, in this case, the optimal focal length of the camera lens will be 8-10 mm. The viewing angle at these values will be about 35°, and is quite suitable for video surveillance of a garage at a distance of 10 meters. Below is a detailed table with viewing angles of cameras with different focal length parameters and matrix sizes.
If you need to change the viewing angle from time to time, or in any difficult situations when determining the focal length before purchasing a camera can be problematic, it is worth purchasing cameras with a varifocal lens that allow you to manually adjust the viewing angle. The FR range of such cameras usually lies in the range of 2.8-12 mm. When using varifocal lenses, you can zoom in or out without losing quality thanks to the optical zoom of the lens.
Which viewing angle should you choose?
The answer to this question depends on the specific task, because each situation is individual. For example, for video surveillance of a large area without the need to select a specific object, cameras with a wide-angle lens of 2.8-3.6 mm and a viewing angle of 70-140° are used.
The viewing angle of 60° is similar to the viewing angle of the human eye and is an average value. Cameras with this angle are capable of transmitting a detailed image with a range to the observation object of up to 10 m.
Cameras with a long-focus lens and a narrow viewing angle (10-30°) are used to observe distant objects, the distance to which can vary from 20 to 70 meters, and depends on the FR of the lens.
There is one interesting feature that allows you to determine the distance of confident recognition of an object, and can serve as a kind of cheat sheet when choosing a camera. It consists in the approximate equality of the focal length, expressed in millimeters, with the confident recognition distance in meters. For example, a camera with a 1/3-inch sensor and a lens with a focal length of 12 mm will be able to recognize a human figure at a distance of 12 meters. At this distance, the size of the observed zone will be 3 meters in height and 4 in width, which will make it possible to confidently identify a person.
2 comments
Correct errors in the article on choosing a lens. “Having calculated the formula, we found that the FR of the lens should be equal to 16, but there is one more nuance. It is very important that the camera’s viewing angle is larger than calculated, otherwise nothing else will be visible except the object being observed. Therefore, in this case, the optimal focal length of the camera lens will be 20-28 mm.”
With a 20-28mm FR, the viewing angle will be NARROW than for the 16mm FR you have chosen.
When planning to deploy a video surveillance system, you inevitably ask yourself: where and how many cameras should you install? How to determine the best places for their location to avoid “blind spots”? At what distance from the objects of observation should the cameras be installed so that the result is a sufficiently clear image of the necessary details?
The appearance and quality of the image are greatly influenced not only by the parameters of the video camera and lens, but also by their correct combination. So, sometimes an excellent, expensive lens can produce an even worse image than a cheap alternative model.
Let's talk about the main factors influencing the quality and scale of the video image, which should be taken into account when choosing a lens for a camera in order to make the most of their capabilities and at the same time avoid unnecessary costs.
Lens viewing angle
One of important characteristics CCTV systems is the viewing angle of the lens. The number and possible locations for installing cameras at the site directly depends on it. The viewing angle of the lens determines the size of the visible object and the scale of the image in the frame.
From this diagram it can be seen that the viewing angle is directly affected not only by the focal length of the lens, but also by the dimensions of the matrix:
And if the focal length is quite easy to determine, knowing the lens model, then with the size of the matrices it is not so simple.
Video camera matrix size
Depending on the aspect ratio (4:3 or 16:9), matrices with the same diagonal have different physical dimensions (Table 1). Therefore, for example, a camera on a 1/3’’ matrix with an aspect ratio of 4:3 gives a larger viewing angle vertically and a smaller one horizontally than a camera on a matrix with the same diagonal but an aspect ratio of 16:9.
| Matrix format | Matrix diagonal (mm) | Aspect Ratio | |||
| 4:3 | 16:9 | ||||
| Width (mm) | Height (mm) | Width (mm) | Height (mm) | ||
| 1/4 | 4.23 | 3.39 | 2.54 | 3.69 | 2.08 |
| 1/3 | 5.64 | 4.52 | 3.39 | 4.92 | 2.77 |
| 1/2.8 | 6.05 | 4.84 | 3.63 | 5.27 | 2.96 |
| 1/2.7 | 6.27 | 5.02 | 3.76 | 5.47 | 3.07 |
| 1/2.5 | 6.77 | 5.42 | 4.06 | 5.90 | 3.32 |
| 1/2 | 8.47 | 6.77 | 5.08 | 7.38 | 4.15 |
In order to facilitate the selection of compatible optics and calculation of viewing angles, the closest standard value for the matrix diagonal is usually declared: 1'', 1/2'', 1/2.5'', 1/2.7'', 1/2.8'', 1/ 3'', 1/4''. At the same time, it is usually measured in vidicon inches. This unit of measurement, equal to 2/3 of an ordinary inch, was introduced since the birth of television, when the receiving element in the television camera was an electronic tube (“vidicon”), and the size indicated its diameter (into which the shot frame had to fit with a margin).
In addition, you must remember that in some camera operating modes some of the matrix pixels are not used. Therefore, when determining the viewing angle, one should talk not so much about the size of the matrix, but about the size of the active area of the matrix.
For clarity, here are a few examples:
N1000(Fig. 2): for everyone possible modes During operation, the active area of the matrix remains unchanged.
Matrix size: 3.7 x 2.77 mm, diagonal 4.62 mm = 1/3.67 vidicon inches (closest value 1/4’’).
N37210(Fig. 3): depending on the operating mode, the active area of the matrix changes by almost 30% vertically and 25% horizontally.
Matrix size: 5.71 x 3.14 mm, diagonal 6.52 mm = 1/2.6 vidicon inches (closest value 1/2.7’’). At a resolution of 1024x768, the size of the active area of the matrix is reduced to 4.58 x 2.32 mm.
BD2570(Fig. 4): depending on the operating mode, the active area of the matrix changes by almost 50% vertically and 25% horizontally.
Matrix size: 5.61 x 4.31 mm, diagonal 7.08 mm = 1/2.39 vidicon inches (closest value 1/2.5’’). At a resolution of 1280x720, the size of the active area of the matrix is reduced to 4.22 x 2.21 mm.
From these examples it is clear that the size of the matrix may differ from that indicated in the passport, and the size of its active region may vary depending on the operating mode.
However, when calculating the viewing angle, one should take into account not only this feature, but also the fact that aberrations of a real lens lead to more complicated calculations.
Most lenses used in CCTV improve image quality by increasing the complexity of the optical system in order to reduce aberrations that affect resolution. This often results in increased geometric aberrations such as distortion (Figure 5), which are perceived as a side effect.
For example, positive distortion reduces the viewing angle disproportionately quickly as the active area of the sensor decreases (blue frame in Fig. 6).
This effect is observed both when changing operating modes of the same camera, and when installing the lens on matrices of different formats. For example, the apparent viewing angle of an 8 mm distortion lens on a 1/2 matrix can be the same as that of a 6 mm lens, and on a 1/3 matrix it can be the same as a 7 mm lens.
The disproportionate decrease in the viewing angle of a real lens with positive distortion is explained by a shift of the focal plane in the center of the frame, in contrast to an ideal lens (Fig. 7), for which the relations are correct
Thus, it is possible to predict quite accurately what the quality and scale of the video image will be for a “camera-lens” pair only if we take into account all the parameters of the video system that affect this. allows you not only to calculate the field of view and viewing angles, but also to select suitable lenses for BEWARD cameras.
