How to read the camera specifications

In the video camera circle, the technical indicators in a color page actually cover most of the technology. If you don’t believe it, there are several people who dare to say that he knows it well. No matter whether it is a salesperson or a contractor, the first thing to get is A coloring page, and most of the color pages are bragging. Only after the final technical indicators are "slightly" somewhat learned, let everyone do it today:
It is expected that "knowledge articles" and "practice articles" will be articles of knowledge. In my opinion, actual combat articles will be provided by the information provided by everyone. Everyone will practise drills together. Those who wish to play in the museum may also participate in the exercise to increase their interest...
Before clarifying the technical indicators, it is necessary to clarify the following things:

1. The imaging element is the CCD! (Of course there are C-MOS), mainly divided into color, black and white, 1/3", 1/4", 1/2" and brand,

size:
The difference in size is mainly sensitivity, which is the minimum illumination, 1/4 illumination will be worse than 1/3, the principle is very simple: the same number of photosensitive points, each point placed on the 1/4 must be smaller, he The light received is less, of course, the illumination is poorer, the advantage is cheaper, there are smaller, the board can be smaller.

Brand:
In terms of price, from expensive to cheap, they are Sony, Panasonic, Sharp, and A1 (LG).
If you use Sony's usual logo "Sony Super-HAD CCD", which is a registered trademark of Sony, or the low-light monogram "Sony Ex-View CCD" has a process called "HAD" during the manufacturing process of the CCD, The CCD of that house can be called "HAD CCD, but Sony improved the process and thought that the quality of the CCD produced was better. It was called "Super-HAD" and registered this name, so only Sony has the so-called Super-HAD. CCD, often seen in the general record "1/3" Sony Super-HAD CCD" is like this, can not mark "1/3" Sharp Super-HAD CCD" That would make a joke.
Ex-view is the Sony CCD registered proprietary name, emphasizing illumination is lower than Super-HAD, of course, the price is much more expensive, other features and pins are similar to the original Super-HAD.
Instead of using Sony's, only "1/3" Color CCD "2 pixels:
In the PAL system, there are 752 (H) x 582 (V), which is called 440,000 pixels, and 500 (H) x 582 (V) is also called 250,000 pixels. In NTSC system, there are 768 (H) x 494 (V), also known as 380,000 pixels, and 510 (H) x 492 (V), which is the so-called 250,000 pixels, 440,000 pixels, is called high resolution, and 250,000 is called low resolution, general solution or middle solution. The above-mentioned pixel refers to "effective pixel 3. resolution:
This is more fun, 25-megapixel camera, the technical limit is about 320, more than a decade ago, Taiwan produced a video camera, probably between 280-300, but compared with the Japanese goods is worse In one piece, what should I do? Then the standard 350 line is good, and later there is a new company and South Korea out, about 300 or so, so the standard 380 good, and in recent years, the mainland has also come out, what can I do? So standard 420 is good! Now, all of them are marked with 420, and there is also a standard of 450 shameless. Even more puzzling is that, whether it is in Taiwan or the mainland, sent to the inspection, it is actually 420? Really bizarre!
And 440,000, the technical limit is probably about 480 lines. Generally speaking, Taiwan, South Korea will probably make it between 400-450. In the same way, the standard is 480,500,520,550! Each conscience.
Also, the recent popularity of the so-called 520 line is a big scam. Why did he say 520 lines? Because the main chip used Sony HQ1 (CXD3172AR), turned over the original data, can not find the word 520, only the unofficial statement: there are 520 lines, but only Y / C output. Therefore, as long as the HQ1 program, we will mark 520, in addition to irrigation method, 550 and 560 came out, it is estimated that 580 is also there.

4. Minimum illumination:
The simplest definition: In the darkroom, the camera is facing the object to be measured, and then the light is slowly dimmed until the measured object is not clearly visible on the display. At this time, the illuminance of the amount of light is the minimum illumination. It's vague enough! In fact, we must consider using a few millimeters of lens, how much light into the camera AGC must be turned off, the video signal is down to how much IRE and so on. Few manufacturers will do this test.
That... the old story came again. Long time ago, Panasonic and Sony's machine had a low standard of 1.1Lux (F1.2), and if Taiwan did it, it would have a mark of 0.5. Later, it would have to be 0.2, and you would mark 0.2. Standard 0.1, he standard 0.05. That's all.
Also, high-resolution CCD illuminance will be worse than low-resolution, or old saying, the same chip area, one placed 440,000 points, one placed 250,000 points, that big point?

5. Signal to noise ratio:
Any circuit will generate noise as long as it is powered on, including the components and the line itself. Of course, the smaller the noise, the cleaner the picture looks. We use the ratio of the video signal to the noise to indicate that the bigger the better, of course. Mathematical formula is 20log (V2/V1), V2 refers to the video signal, V1 refers to the noise size, the unit is "dB"
Or the old story, long time ago, Matsushita and Sony's machine noise ratio than the standard 50 dB, that made it on the standard in Taiwan ... ... Oh! One seems to be rather poor, I'm sorry to brag, then the standard 48 is good, but does not look good? Modify it: "More than 48 dB", so ">48dB" is this way, regardless of the A-Cat dog made by the camera, will be marked this way, there is to test? I gave him his head!

6. Electronic shutter:
In order to make the image brightness correct, we must correctly control the amount of light into the camera, to adjust the amount of light from the lens aperture and the camera shutter, generally we use the manual lens, the aperture adjustment will not move, if this time What should I do with glare? It is very simple, before the CCD has not been exposed, DSP will quickly "sweep" the signal on the CCD, that is, catch light faster when the light is strong, slower when the light is weak, grab once equivalent to my door SLR camera When the "click" sound, SLR camera is a mechanical shutter, we are electronic, so called "electronic shutter"
According to DSP specifications, the electronic shutter speed is 1/50 second to one hundred thousandth of a second in the PAL system, so everyone has marked this. If the camera is poorly tuned for practical applications, it is less than 100,000. One, if the camera looks like a thin layer in the sun, it is not very clear, that is, the shutter speed is not enough.
In addition, if an auto iris lens is used, the amount of light entering is controlled by the lens aperture. At this time, the shutter speed of the rear camera itself is set at 1/50 second. 7. Gamma compensation:
What is Gamma? Simple explanation, CRT tube is based on the strength of the electron beam hit on the screen to determine the brightness generated, the stronger the stronger the fight, but not 1:1, that is, after a strong time will not be Proportionally bright, this is the characteristics of the CRT tube, so the video output has to do some deliberate enhancement at high brightness, which is called Gamma compensation, a compensation curve called 0.45, as long as the next instruction to the DSP is just fine, There is no technology at all, and some cameras will add a switch, allowing you to choose 0.45 or 1, 1 of the compensation curve is 1:1, in some bright light environment is also quite easy to use (under strong light, non-backlight under)

8. Backlight compensation:
What is the backlight compensation, which is related to the shutter speed, for example, when a camera is mounted on the ATM, facing the street, in the big sun, the environment is very bright, so the camera shutter speed is of course very fast. Will not be overexposed. At this time, if someone withdraws funds, the face is facing the camera. Because the camera is currently fully metered, it is basically affected by the environment and the whole is still very bright. Under the high-speed shutter, the exposure of the face is insufficient. Obviously dark, this is the “backlight” mentioned above in photography, that is, there is a strong light on the back, which causes the subject to underexpose and turn black.
So the problem lies in the overall exposure. If we only take a part of the surface to measure the light, for example, in the middle, the face is in the middle of the stroke, when the DSP will measure underexposure, it will slow down the shutter speed. At this time, the human face is clear, but because the shutter speed is slow, the background (street) is overexposed and white.
Therefore, backlight compensation is based on a specific metering area, adjust the electronic shutter (or auto iris), so that the exposure value in the metering area is normal, not in the metering area, regardless of the metering area set by the DSP parameters, Usually take the middle 1/9, or add the bottom 1/3 into a convex font.
As for what is "wide dynamic", it will write another article to talk about.

9. Synchronization system:
Synchronization inside, outside synchronization and power synchronization.
Power synchronization,
To put it in a long story, simply put, it is to make the timing of each camera's loss of map field consistent. For example, if the speed of each enemy is the same, if everyone has the same speed, if no one is whistling or shouting at the side, The pace is not consistent, this function is used in the matrix switch, the screen will not shake and then return to normal, otherwise the administrator eyes do not spend, to achieve power synchronization must be added to the power synchronization circuit, plus a switching power supply Synchronous signals are taken from alternating current (power is fixed for 50 weeks) as the basis for synchronization.
In addition, in the NTSC system, because the oscillation frequency in the DSP can not be consistent with 60 weeks of commercial power, there will be color rolling in the light, especially the Sony 2163 program is more serious, then you have to add power synchronization to solve, forced to DSP The frequency is consistent with the light.
In addition, the AC power supply used by us has three phases, which are 120 degrees different from each other. If the power-synchronized cameras are connected to different phase power supplies, there will be a phase difference that cannot be synchronized with each other. Therefore, a phase adjustment knob is needed to trigger the phases to each other. Adjusted to the same.

External synchronization is triggered by the external step to throw out the screen, this function is now rarely used in the internal synchronization is to output 25 pictures per second, regardless of someone else 10.AGC
It is the electronic automatic gain, it is the basic function of the camera, some people make the screen look bright, deliberately adjusted very high, so that when the low illumination is very easy to white, so some people simply put a switch here, to be high To be low, come on your own for the next few things:

Connector type:
There are C-Mount and C/S Mount:
To tell the story, when the camera was originally made, it had to be equipped with a lens. Therefore, an interface standard was implemented:
"The pitch diameter is 25.4mm, 32 threads per inch, and the distance from the edge to the CCD is 17.526mm."
This is called the C interface. The camera and the camera will match this standard.
At that time, there were eight lenses in the lens. Later Panasonic engaged in a five-glass lens. The cost was saved, but the imaging distance was shorter by about five millimeters. That is, the lens was closer to the CCD by five millimeters. What about? Then change the standard. Change the “Edge to CCD distance of 17.526mm” to 12.5mm. This is a C/S interface. Almost all cameras now use the C/S interface, and then pay a C/S. Extension ring from S to C interface.

Automatic aperture:
That is, the type of auto iris lens that can be connected, there are currently two: video and direct drive (DC), because the direct drive method has to add a small circuit, some inexpensive machines simply removed, Bet you can't afford to buy a DC auto iris lens.

Video output:
The standard is 1 Vpp, which is 1 volt (peak-to-peak), the standard is such a mark, but often manufacturers look for a "bright" point, deliberately increase the strength of the question mark, will cause some in the DVR and wiring Troubled.

Power consumption:
When the general camera is at 12V, it is generally between 90-130mA.
Divided into 12VDC, 24VAC, 220VAC three, usually 24VAC is also compatible with 12VDC