Taking black and white photos with a digital camera: features and difficulties
Actually, the process of shooting black-and-white photographs with a digital camera is no different from both shooting color pictures and shooting on film. Nobody canceled the laws of light. You just need to learn to see the world in black and white. This understanding comes only with experience, when you shoot a lot on black and white film. This experience is much more difficult to achieve with digital cameras these days. At one time, about thirty-five years ago, I learned about a special survey filter “panvision”. This filter is magenta in color. When viewed through it, the filter changes the color sensitivity of the eye so that it is close to the tone rendition of black-and-white film without a filter. That is, when you look through it, you just see a black and white photograph. It was necessary to look through this filter, not to remove it. But I never managed to hold it in my hands.
Speaking about recording an image, in the camera settings you should immediately disable the option “Shooting in black and white mode”.
And shoot only in color, in RAW format, or at least in JPEG. You will understand why this is so in this small series of articles on digital black and white photography.
A few words about filters
The use of most filters in modern digital photography differs significantly from their use in classic black and white photography. And although some light filters are not used at all in digital photography, understanding how they work when shooting on black and white film helps to imagine how the picture will look after it has been converted to black and white using software methods.
For example, an orange filter darkens blue and purple. This filter makes the clouds stand out against the sky very well. Good for nude shots in daylight. This is perhaps the most common filter used by photographers shooting on black and white film.
The top image was taken without a filter, the bottom image was taken using dark orange. While I was putting on the orange filter, the clouds shifted slightly to the left, this can be seen in the second frame.
But color filters designed for black and white film photography are not suitable for shooting with modern digital cameras. Even if you shoot in RAW format, the image comes out with a strong tint to the color of the filter itself. This turns out to be a serious limitation when further converting the image to black and white. In addition, it will be almost impossible to return to the color version of the photograph. If the shooting is carried out only in JPEG format (in the “black and white shooting” mode), then there is no chance of getting a color photo at all, since the camera will save only a black and white image. There are many more creative techniques for converting a color digital image to black and white, not using a camera, but using various RAW converters or Photoshop.
Another reason why color filters are not suitable for black and white digital photography is the design of the camera sensor. As a rule, a Bayer lattice is used in matrix construction. In it, two pixels register the luminance values for green, and one for red and blue. That is, when shooting through a color filter, it will block certain colors. The use of a red or blue filter will mean that only three quarters of the matrix pixels are registered, and with a green filter, the working pixels will be half as much. This is enough to significantly reduce image quality and lead to various artifacts in smooth tonal areas such as the sky.
An exception is the UV filter, which is also used in color photography. In addition to blur, it also eliminates bluish tinge, especially in highlands.
If we talk about other filters, then almost all of them can be used. However, with some reservations.
As the name implies, these filters do not change the spectral composition of light. They are used in both black and white and color photography, and are only used to increase exposure. Imagine you want to shoot a fountain so that the water does not look “frozen” due to a short shutter speed, but it is important to maintain the same depth of field. The light is quite bright and the shutter speed at 22 aperture is 1 / 30th of a second. Putting on a ND filter with a factor of 8 (3 stops), we get a pair of 22. 1/4 of a second. As a result, the water will be perfectly lubricated. The use of filters of high magnification (60–10000) will allow, for example, to shoot a crowded city square in daylight as if there was no one on it. At a shutter speed of 30–120 minutes, all moving objects on the film simply will not appear, since they move too quickly relative to the exposure time. It is still impossible to shoot at a figure with such a shutter speed.
The picture was taken using a ND filter, which made it possible to increase the shutter speed. Due to the relatively long shutter speed (4 seconds), the water is blurry.
For color photography, it is often important to get a richer sky or remove bright highlights from the water. For this, a polarizing filter is used. However, there is always a risk that such a photo, after being converted to black and white, will become boring and lifeless. In addition, after converting the image to black and white, pronounced stripes may appear in the sky. Therefore, if you plan to end up with black and white photography, shoot with or without a polarizing filter. Or just take takes at different angles of rotation of the polarizing filter.
Since both polarizing filters and ND filters increase exposure, be prepared to use a tripod in most cases.
The picture was taken using a polarizing filter. Since the shooting was carried out with a wide-angle lens, approximately 45 ° against the light, the darkening of the sky is different from different sides of the frame. In the right part of the frame, the sun is closer, because there was practically no darkening of the sky. With this direction of light, when shooting with a wide-angle lens, the sky will have different brightness. However, the foliage in the left picture looks more impressive.
Both images were converted to black and white using the Black White command in Photoshop. Unfortunately, in the first photo of this pair, the sky has become somewhat striped in the upper left corner. In order to avoid “banding” in such areas, the image should be converted to black and white at 16 bits per channel.
If the shooting was carried out from a tripod, during processing, you can make combinations of shooting takes with different angles of rotation of the polarizing filter and, thereby, achieve reflections and highlights in certain parts of the image so that it meets the artistic intent.
- If you plan to convert a color digital image to black and white, you cannot use the color filters for classic black and white photography.
- You should also avoid using conversion and color enhancing filters.
- Polarizing filters should be applied based on specific needs.
- Various ND filters and any attachments can be used without restrictions.
- When using any filters, the following rule must be observed: the effect of the filter should not overwhelm the photo.
This is the main rule when using any filters.
Converting color originals to black and white
Before converting color images to black and white, complete retouching of the image should be performed, if necessary. Despite the fact that almost all RAW converters can be quite flexible in converting a color photo to black and white, there is a significant category of images for which the settings and tools of the RAW converter are not enough. When to carry out toning also depends on the image itself. For some I do toning before converting to black and white, for others after. If before, then at the final stage, sometimes a small ton-correction follows again. In the RAW converter, you can immediately observe the process of converting to black and white image and toning.
In the following articles, we will talk about converting photos to black and white in the RAW converter and various methods in Photoshop.
Black and White Camera Document: Taking Black and White Photos with a Digital Camera: Features and Difficulties
Features of the ultra-compact document camera DOKO DS13MU
I must admit that I had not received this new DOKO Visualizer for testing yet, just studying its sent characteristics, I was very skeptical. Well, yes, the developers took the already proven model of 2018 DOKO DS13FS as a basis and equipped it with VGA and HDMI inputs (the DS13FS already had the corresponding outputs). Yes, it is now possible to transmit video signals from an external source (for example, a computer or laptop) through a VGA and HDMI camera and switch from a broadcast computer image to a “live” image of the observed scene (and vice versa) by pressing one button. Yes, they replaced the flexible tripod with a folding mechanical one. Of course, this is all interesting, and sometimes it is really necessary. but the price has also increased by a third! And only after taking it out of the box and taking it in my hands for the first time, I appreciated the beauty of this camera! Yes, exactly beauty. after all, the design of any device is its appearance, its attractiveness. So it’s nice to look at this camera, hands just reach out to touch it, turn it, turn it on and work. Everything is thought out to the smallest detail, everything is very compact and functional. When folded, it is so tiny (19x8x2.5cm) that it is comparable in size to a bar of chocolate, fits even in a jacket. and its weight does not exceed 600 grams.
And at the same time, in terms of functional equipment, this device is a full-fledged modern document camera: high quality of generated images, a wide range of sizes of observed objects (documents), a good set of presentation effects, the ability to work both autonomously and with a connected computer. In short, DOKO DS13MU can rightfully be called a new generation ultraportable document camera, a must-have accessory for field lectures and presentations. It is not for nothing that its set includes a special bag-case for carrying.
As expected, to begin with, we give a table of the main characteristics of the camera.
Auto / Daylight / Incandescent / Manual
Text / Graphics / Black & White / Negative / Sketch
Freeze / Select / Mask / Spread / PIP / Slide Show
VGA (15-pin D-sub), HDMI (mini HDMI 1.3)
Single frames to built-in memory / SD card / PC
13M (4160×3120) / 8M (3264×2448) / 5M (2560×1920) /
117 MB (up to 500 frames 1024×768 / 200 frames 1600×1200 /
90 frames 2560×1920 / 55 frames 3264×2448 / 35 frames 4160×3120)
DC 5V 1A (via AC / DC power adapter 100-240V, 50-60Hz)
7 watts (non-illuminated) / 4.4 watts (illuminated)
AC / DC power adapter, HDMI and USB cables, control panel, microscope adapter set, anti-glare sheet, quick start guide, CD with software and manual
Basic elements of the camera
The design of the chamber is as follows:
|one||Camera lens||9||Security slot|
|2||Backlight (3 brightness levels)||ten||HDMI input|
|3||Swivel chamber head||eleven||HDMI output|
|four||Camera control panel||12||VGA input|
|five||Slot for installing an external SD card||thirteen||VGA out|
|6||Receiver of IR signal from the control panel||14||USB port for connecting to PC|
|7||Built-in speaker||15||DC 5V power connector|
|8||Receiver of IR signal from the control panel||16||Built-in microphone|
For a general understanding of working with the camera, it is necessary to present a diagram of its connection to external display devices (TV-monitor, video projector) and to a computer.
To display images from a camera on a monitor (video projector), the VGA OUT or HD OUT connectors of the camera must be connected to the VGA IN or HDMI IN inputs of the monitor, respectively. Switching between VGA and HDMI outputs is performed by buttons on the control panel, while VGA resolutions are available at 1024×768 and 1600×1200 (aspect ratio 4: 3), and for HDMI. 1280×720 and 1920×1080 (aspect ratio 16: 9). The choice of output resolution is carried out through the on-screen menu.
But to implement the pass-through transmission of a VGA (HDMI) signal from a computer (or other source of external video signal) through the camera to an external monitor, you must connect the VGA IN (HD IN) connector of the camera to the corresponding output of the computer.
It should be noted here that to switch the camera’s output signal from an external (computer) image to the image formed by the camera itself (or vice versa), it is necessary and sufficient to press the “PC” button on the camera control panel. This function is very important in the real conditions of a school lesson, lecture or report, since it allows you to flexibly control the presentation, to combine pre-prepared computer images (slides) from the laptop screen with “live” images of objects (documents) from the desktop. But it must be admitted that such a switch does not occur instantly, but in about 5 seconds. at this time, there will be no signal at the camera’s output (a black screen will be observed on the external monitor). It is also important to note that when disconnected, the camera automatically switches to the pass-through mode, independently detecting the presence of an active signal at the input (however, the camera must remain connected to the mains).
When connected to a computer via USB, 2 modes are available: Disk and Camera, switching between them is performed through the on-screen menu. In the first mode, the computer will open direct access to the camera’s memory (like an external computer drive): either the built-in memory (117 MB capacity) or an external SD card (up to 32 GB). It is important to note here that priority is always given to the SD card. if it is installed, then both writing and reading will be performed from it. In the second mode, the computer recognizes the connected device as a regular USB camera, which allows it to be used, for example, with programs such as Skype. But of course, the deepest integration and control of the camera is achieved within the original SmartDC Pro program included in the package.
First of all, for this, you can use the buttons on the control panel of the camera itself (located on the front surface of its base):
As you can see, they provide access to the basic functions of the camera, from selecting the video output signal to storing snapshots and videos in the camera’s memory, from turning on the backlight to adjusting the brightness of the image. Most of these commands are duplicated on the IR remote control. But only with its help the user gets access to such functions as manual focus adjustment, presentation effects (Mask, Highlight area and Picture-in-Picture), changing the sound volume and turning on the MACRO focus mode. detailed settings, including control of display functions, selection of values for various camera parameters (output video signal resolution and image size, USB mode and display modes), are available through the multi-level OSD menu:
And the Viewer OSD menu allows you to control playback options, delete recorded image / video files or get detailed information about them (INFO):
And finally, some camera functions (zoom, autofocus, brightness) can be controlled via USB directly from a computer using the supplied SmartDC Pro software.
The camera is equipped with a CCM lens from Sony (CCM. Compact Camera Module, assembled with a registering CMOS matrix). It has a built-in micromotor for autofocus function. The matrix resolution (Sony IMX214) is 13.13 million pixels, which is perhaps a record for this class of equipment today. At first glance, this seems even superfluous, since the maximum output resolution of the generated images does not exceed 2 million pixels (1600×1200 or 1920×1080). This is why many competing models still use a 2M matrix. But practice confirms that the higher the recording resolution, the higher the quality of the output image (visually “clearer”, more detailed). This is especially noticeable when using digital zoom. over, such a 6-fold “reserve” in the resolution of the recording matrix allows, when displaying the observed objects, to implement the so-called smart-zoom. a zoom function without loss of image quality, equivalent to optical zoom (more on this below).
In addition, we must not forget that the camera allows you to capture and save in its own memory (and then transfer to the computer) individual frames (photographs) of the observed objects. Thirteen million pixels correspond to a 4160×3120 frame at an aspect ratio of 4: 3 or 4800×2704 at 16: 9. The quality of digital scans of documents obtained with such a resolution turns out to be sufficient for effective text recognition. Thus, this model can be used as an express scanner for various documents in formats from A10 to A3-. And being connected to a microscope (a set of adapters for eyepieces of various diameters is included in the delivery set), it turns the latter into a modern digital instrument for observing micro-objects. However, here we must warn against excessive optimism. in the images formed by the camera, trapezoidal geometric distortions are observed at the edges of the field of view, which is quite acceptable for the purposes of visual observation, but for scientific measurements it may turn out to be unacceptable.
According to the specification, the camera has a total zoom of 16X. And although the camera lens has a fixed focal length, i.e. does not provide optical zoom, of these 16 times, pure digital zoom is only 8X. But additional 2X are provided by using the redundancy of the resolution of the recording matrix, which in fact is equivalent to optical magnification. This technology has been known for a long time and is actively used in older models of document cameras from various manufacturers (under the names AverZoom, Smart Zoom, Extension Zoom, etc.). Let’s dwell on this technology in more detail.
According to the general scheme of the document camera, the formed image of the object, passing through the lens, enters the CMOS matrix, consisting of separate recording elements (pixels), in which it is converted first into an electrical and then into a digital signal. The resulting digital image is recorded in the camera’s memory and transmitted to the camera’s output. The enlargement of the image means that a smaller area of the observed object is focused on the recording matrix, but it is fixed with the same number of pixels, so that at the output (on the screen used for displaying a monitor or video projector) we see a more detailed image of this area. Thus, an increase in the image is equivalent to an increase in the number of recording pixels per a given area of the observed object. Here it is important to emphasize once again that it is the number of pixels of the recording matrix that is of fundamental importance, it is it that is responsible for the detailing of the image, for its information saturation. Although from the point of view of convenience of visual perception of the displayed image, both the screen size and the acceptable value of the resolution of the used display device are important. But the detail of the image does not change.
In the simplest case, a camera lens consists of a single fixed focal length lens. The method of magnification available in this case is the mechanical approach of the observed object to the camera lens (sometimes it is even called mechanical magnification). In this case, a smaller area will be focused on the recording matrix, respectively, it will have a larger number of pixels. and at the camera output we will observe its more detailed image.
However, there is also another possibility. “Guess” (mathematically calculate, that is, interpolate) the estimated values of the image between the available pixels of the recording matrix and thereby, as it were, increase the selected area of the image. This uses the built-in Digital Signal Processor (DSP) of the document camera. This approach is called digital zoom.
It is important to understand that in this case the real detail of the image does not change in any way, new information about the observed object does not appear. And the visual quality of the image area enlarged in this way is rather low, pixelation and / or “blurring” appear (depending on the processor power and the implemented interpolation algorithm).
sophisticated lenses consist of multiple lenses that can move relative to each other. Moving the objective lenses forward and backward, the degree of magnification of the object is changed, focusing on the area of the recording matrix an image of a larger or smaller area of it. In this case, the optically enlarged section of the observed object completely falls on the same sensor, so that all the available pixels of the matrix fall on it. The resulting image at the camera output is sharper and more detailed. This is real optical magnification.
It is not difficult to understand that its implementation requires complex and expensive lenses (the more difficult and more expensive, the higher the resulting magnification provided), which only older models of Visualizers are equipped with. But recently, a new approach to magnification has appeared, based on the use of recording matrices with an increased number of pixels. The fact is that if the resolution of the camera’s output signal is limited to 2 million (2M) independent display elements, and the recording matrix has 8M pixels, then there are 4 matrix pixels for each displayed element. Accordingly, the detailing when registering an image along each of the axes is 2 times higher than the visualization capabilities. And such redundancy can be easily used to enlarge the displayed area of the image, simply by using “hidden” (non-displayed) pixels. Of course, in this operation, you still have to use the camera’s digital processor, but when calculating it will rely on the available real values. And the resulting magnification will be virtually equivalent to optical.
It is this approach called Smart Zoom that is implemented in the DOKO DS13MU camera. However, it is limited to a value of 2X. although the seemingly available “reserve” of the effective number of recording pixels (13.13M versus the required 2.07M) allows you to achieve an increase of 2.5X. In fact, such a simple calculation is erroneous because it does not take into account the aspect ratio. The fact is that the value of this ratio for the output HDMI signal (1920 × 1080) is 16: 9, while the Sony IMX214 CMOS matrix has 4208 × 3120 active pixels and is characterized by a 4: 3 ratio. Accordingly, on the larger side, the maximum magnification is limited to 2.19 (4208: 1920). For additional considerations of the accuracy of the implementation of the corresponding algorithm, it was decided to set the Smart increase value for DOKO DS13MU as 2X.
Flexibility to adjust the field of view
A folding mechanical camera tripod consists of two legs with a maximum camera head lifting height of 35 cm. Additional freedom of adjustment of the field of view is provided by the ability to rotate both the camera head itself (± 90º) and the lens inside the camera head (by 90º). using the corresponding wheel.
It is useful to note that the combination of lens rotation by 90º with the function of mirror image reflection (FLIP command on the panel or control panel) provides an additional opportunity to rotate the generated image by 90º / 180º / 270º / 360º.
Large capacity on-board memory with direct access
The camera has both built-in memory and a slot for connecting external SD memory cards. The internal memory is used for recording and storing individual frames, and video clips (with sound from the built-in microphone) can also be recorded on the SD card. The recorded data in playback mode can be viewed either individually or all in a row (similar to a slide show, but with automatic playback and video files). As for the resolution of the captured frames, there are 4 values to choose from: 13M, 5M, 2M and 0.8M. The built-in memory capacity of 117 MB is enough to store up to several hundred frames (the memory is non-volatile, so its contents are retained when the power is turned off). It is important to note that the size of the picture in pixels will depend not only on the selected resolution value, but also on the set aspect ratio of the video output. If the VGA output is set to active using the buttons on the camera control panel, but this ratio is 4: 3 and, accordingly, the 13M resolution corresponds to a 4160×3120 frame, 5M. 2560×1920, 2M. 1600×1200, 0.8M. 1024×768. But if the HDMI output is active (aspect ratio 16: 9), then when you select 13M, the frame size will be 4800×2704, 5M. 2944×1632, 2M. 1840×1024, 0.8M. 1168×640.
(with VGA / HDMI)
Average file size with frame
Number of frames in internal memory
Dead pixels compensation
All dies produced by SONY pass 100% final inspection, but not all of their shortcomings are the reasons for rejection. A typical malfunction associated with the formation of a “white” point is not a reason for rejection, because with a sufficient level of illumination does not appear visually.
However, in low light conditions, for example, when working in night mode, such “dead” pixels clearly stand out against the general dark background in the form of bright white dots.
The new processor provides the ability to automatically search and compensate for up to 64 such pixels, which is performed by the user through a special menu command. In real CCD matrices, the number of such pixels rarely reaches 3-5 pieces. Thus, all “dead” pixels, not only existing in the new CCD matrix, but also arising in it during operation, can be compensated.
The state of the “inoperative” pixel is calculated as the average value of the pixels adjacent to it, and therefore, after compensation, it becomes indistinguishable both in the daytime and at night.
Analog cameras are characterized by this feature. when displaying elements located at an angle to the horizontal axis, as well as small alternating contrasting objects, moire appears on their borders, as well as colored stains in the form of multi-colored stripes.
This feature is associated with the fact that the chrominance signal of an analog camera is encoded at a certain frequency, and when the luminance and chrominance signal processing paths are insufficiently matched, the moiré effect appears.
The function of suppressing moiré allows you to exclude color “streaks”, which is achieved due to a higher processing frequency, and as a consequence of better consistency of the paths for generating signals of luminance and chrominance, as well as due to special algorithms for processing contrast transitions, incl. and alternating.
Intelligent IR power control
Experts know that often the wrong selection of IR illumination significantly degrades the image quality in night observation. In this case, one part of the scene is flooded with white light, and the second remains dark with indistinguishable details.
There are two reasons for this problem: first. wrong design of IR illuminator, second. excess power of IR LEDs.
To eliminate the latter drawback, the new processor, in addition to the D-DWR mode, provides dynamic control of the power of the IR illuminator, based on the analysis of the illumination level, while the backlight power increases as the image brightness decreases, i.e. compensates for the lack of light, and does not turn on or off according to the sensor signal, as in conventional cameras.
Control of car parking zones
The processor allows you to superimpose the markings of the parking zones on the image, which greatly simplifies the monitoring of parking lots and control of the uniformity of the distribution of cars on them.
Below are the images with the parking area monitoring function enabled.
Remote configuration capability
As noted earlier, all camera modes can be configured via the OSD menu. In this case, some of the parameters can be adjusted only during the day, at high brightness (BLC, AE, D-WDR, LSC), and some. only in the dark (HLC, 2D-NR, Smart-IR).
As a rule, the configuration is performed from the joystick built into the camera.
But besides this, the cameras are equipped with an RS-485 interface with which you can remotely enter its menu using the control commands of the Pelco-P or Pelco-D protocols available in most telemetry control panels. This possibility greatly simplifies the setup of CCTV cameras installed in hard-to-reach places, and can be performed after installation, taking into account the specific features of its operating conditions, taking into account the accumulated wishes.
LSC. lens unevenness compensation
Popular wide-angle lenses with f = 2.5 and 2.8 mm are characterized by reduced light transmittance at their edges, resulting in image shading at the corners.
LSC (Lens Shading Compensation) mode eliminates this effect of the lens. The operation of the camera in this mode is shown in the following images:
Like all previous functions, this function is also configurable via the OSD, so the degree of compensation can be adjusted depending on the location of the camera.
General information about 600 TVL cameras
In cameras with a resolution of 600 TVL, our company uses a 4th generation video processor, which is characterized by increased digitization of the video signal taken from the color CCD matrix, extended frequency response of video processing paths and the ability to generate CSVB or S-Video output signals using digital-to-analog converters (DAC) built into the processor.
Sintech Dvr setting for blank & white problem
Like all previous processors, the new ISP performs digital image processing and implements a number of functions already traditional for CCTV cameras, namely:
- DN (Day-Night). “day Night”. formation of a black-and-white image in low illumination with the ability to adjust thresholds and delays in the transition between black-and-white and color modes
- AE (Automatic Exposition). electronic shutter allows you to maintain constant image brightness regardless of the illumination of the observed scene
- AGC (Automatic Gain Control). automatic gain control in night mode ensures the formation of a bright and recognizable image in low light and night work
- BLC (Back Light Compensation). backlight compensation with the ability to adjust up to 4 zones, with the setting of the brightness level in each of them relative to the overall brightness level of the image, which allows, for example, to compensate for excessive brightness of windows against the general background of the room
- adjusting the contrast and clarity of the image
Changes to the ISP operation parameters are made by the user through the on-screen menu, with navigation using the joystick built into the camera or through the RS-485 interface in the Pelco-P or Pelco-D protocol.
All CCTV camera settings are stored in non-volatile EEPROM memory and do not change when it is de-energized.
A wide range of video processing parameters allows you to customize the camera and get an ideal image under any operating conditions: in dark and light rooms, outdoors and indoors, when working in backlight and in scenes with a wide range of brightness, as well as in complete darkness when using infrared (IR) backlight.
CCTV cameras of 600 TVL resolution
The heart of such surveillance cameras is a 760H CCD (CCD) matrix with 752×582 effective pixels horizontally and vertically, respectively. This matrix format has long been used in high-definition cameras, including 480 TVL, 520 TVL and 540 TVL cameras.
How is a higher horizontal resolution obtained on a classical matrix??
The answer is simple. like all previous increases in resolution, from 480 TVL to 540TVL, were carried out through the use of a more efficient video signal processor. ISP (Image Signal Processor).
The article describes the capabilities of the new processor and cameras based on it.
Main characteristics of CCTV cameras.
In modern CCTV cameras, charge-by-charge recording devices (CCDs), which form the basis of CCD matrices, are used as a light-to-electrical signal converter. Today most camcorders are manufactured on the basis of Sony, Panasonic, Sharp, LG, Samsung matrices.
Matrix format (inch). the size of the matrix diagonal in inches, which determines the angle of view when using a lens with a particular focal length. The most common CCTV cameras are 1/2 ″, 1/3 ″, 1/4 ″. The larger the matrix format, the larger the camera dimensions, and the matrix dimensions do not in any way affect the image quality indicators.
Resolution (TVL) is a parameter that characterizes the detail of an image, in a word, the higher the resolution, the better small details are seen, such as a car number, a person’s face. It is measured in television lines (TVL), and the horizontal resolution is implied, since the vertical resolution of video cameras of the same standard is the same and is limited at one level (400 TVL for CCIR / PAL standard and 330 TVL for EIA / NTSC). Black-and-white standard-definition CCTV cameras have a resolution of 380-420 TVL, high-resolution 560-570 TVL, color cameras 280-350 TVL, high-resolution up to 460 TVL, and with digital video signal processing (DSP) up to 560 TVL via S-VHS output. details can be found in the article “TVL in CCTV cameras”
Sensitivity (lux). the minimum illumination level (in lux) at which the CCTV camera produces a recognizable video signal. This is the most confusing parameter as there is no clear definition. Most often, sensitivity is understood as the minimum illumination on the object, measured at a lens aperture of 1.4. For conventional black and white cameras, it is 0.4
0.01 lux (twilight), for highly sensitive up to 0.00015 lux (dark night), for color 0.2
3 lux. Sometimes manufacturers indicate the minimum illumination on the matrix, which is 10 times higher
It is worth mentioning that the sensitivity of black-and-white video cameras affects not only the spectrum of visible light, but also the infrared region, which makes it possible to use IR illumination in low light conditions.
Signal-to-Noise Ratio (dB). expresses the ratio of the amplitudes of the video signal to the noise in a logarithmic scale. S / N = 20 log (video signal / noise). In a word, S / N = 50 dB means that the amplitude of the video signal is 316 times greater than the amplitude of the noise. This allows you to observe a clear picture, with S / N = 40 dB, small interference is noticeable, especially in low light conditions. At S / N = 20 dB, there will already be a solid “ripple” on the screen.
Electronic shutter (sec). in other words, the exposure time of the matrix, which provides an average brightness of the image in a dynamically changing light environment. This is achieved due to the accumulation time of the charge in the cells of the CCD matrix, which in bright light can reach 1/100000 sec, thus simulating the auto iris of the lens. Normal and maximum value of the matrix exposure time for CCIR / PAL signal is 1/50 sec, for EIA / NTSC 1/60 sec.
The supply voltage of camcorders is usually 12V DC or 24 / 220V AC.
Synchronization of CCTV cameras is of 3 types. In most cases, internal crystal synchronization is used. In some cases, AC-powered cameras use Linelock synchronization, and DC-powered cameras use external synchronization.
Back Light Compensation (BLC) is a hardware function that allows you to observe an object in front of a bright background.
Digital video signal processing (DSP) in CCTV cameras allows you to significantly expand the dynamic range, use motion detection, switch between day-night, black-and-white and color modes, apply the PTZ function (ZOOM, shift of surveillance zones).
For more information on the main characteristics of video cameras, see the article: Basic settings for video cameras. OSD menu.