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IP CCTV: What does pixel density mean exactly?

IN DEPTH An IP surveillance system may be used to observe and protect people, objects and people s activity inside and outside the objects, traffic and vehicles, money handling in banks, or games in casino environment. All of these objects of interest may have different clarity when displayed on a workstation screen. The image clarity depends primarily on the camera used, the imaging sensor, its lens and the distance from the object.

There is one parameter in IP CCTV that expresses the image clarity in a simple way with just one parameter: pixel density. The pixel density is usually expressed in pixels per metre (Pix/m), at the object plane, although it can be expressed in pixels per foot. Pixel density in IP CCTV sense should not be confused with the display pixel density quoted by various LCD display manufacturers which defines the screen density, in pixels per inch (PPI). The advantage of expressing object clarity with its pixel density is that it combines the sensor size, pixel count, focal length and distance to the object in just one parameter . When using pixel density metrics all variables are included and makes it universally understandable what details you will get on an operator s workstation screen. When designing a system, or a tender for a system, one can request pixel density for a particular image quality. So, instead of asking for a 6 mm lens for your camera in a particular location, for example (which means nothing without knowing the camera sensor it is used on), it would be much more useful if a particular pixel density is defined for the view. This will then be used to calculate the required lens for the particular camera used and the distance from the object. This will guarantee the clarity of the image (assuming the lens is focused optimally and there is sufficient light, of course).

Pixel density can be used for any object that IP CCTV user might be interested in: face, licence plate, playing card, money and similar. Let us now explore how many pixels per metre are attributed to various objects. One of the most commonly referred pixel densities is for Face Identification. Face Identification in CCTV means sufficient clarity of the image so that one can positively identify who the person on the screen is. According to Australian Standards AS4806.2, for Face Identification in analogue CCTV, we require 100% person s height to fit on the monitor screen display. The details of 100% person s height on a screen have been tested many times and it s been verified that they are sufficient for such a person to be identified. We know that PAL signal is composed of 576 active TV lines, so, according to AS4806.2, a person s height would occupy all of the active lines to make it 100%. Head occupies around 15% of a person s height, which is equivalent to around 86 lines (576 x 0.15 = 86.4), which is the same when converted to pixels (assuming recording is made full TV frame mode, which is equal to two TV fields). If we agree that an average person height is 170 cm, the head would occupy around 25 cm of that.

The pixel density at the object, which is required to make a positive Face Identification according to AS 4806.2, can be calculated to be 86 pixels at 25 cm of head height. Since there are 4 times 25 cm in 1 m of height, this becomes 4 x 86 = 344 pix/m. So, one can say that with pixel density of 344 pix/m at the objects plane it should be possible to positively identify a face, according to AS4806.2. Face Identification as per AS4806.2 Some other standards may require different values, and one such (newer) standard is the IEC 62676-4, which defines 250 pix/m to be sufficient (i.e. suggests that with slightly lesser pixel density than the AS standards one should be able to identify a person). Clearly, this number is not fixed in concrete, and it will depend on the observing ability of the operator, as well as other parameters (lens quality, illumination, compression artefacts, etc ), but the key is to understand that such a pixel density can be calculated for any type of camera, irrespective if that is SD, HD, 4k or any other format. The next image quality down, as defined by the standards is for Face Recognition. The details of Face Recognition image should be sufficient to recognise the gender of a person, what he/she is wearing and possibly make an assertion of who that person might be, if picked from a bunch of people that have already been identified somewhere else (e.g. passport or drivers licence photo).

This is basically an image with half the pixel density to the face identification, which according to AS4806.2 should be around 172 pix/m, while IEC62676-4 suggests 125 pix/m. Similarly, pixel density can be defined for vehicle licence plates visual recognition (not software automatic LPR). In the AS 4806.2, this is defined as 5% characters height on a display screen, which is around 30 TV lines (pixels) (to be very accurate 576 x 0.05 = 28.8). If we assume that a typical Australian number plate has characters of around 90 mm in height, than this equates to 11 x 30 pixels = 330 pix/m. The number 11 is obtained from dividing 1000 mm (1 m) with 90 mm. One may say that for visual licence plates recognition similar pixel density is required as for face identification. Licence plate recognition as per AS4806.2 When money and playing cards are observed in banks or casinos, many practical tests have shown that at least 50 pixels are required across the notes or cards longer side in order to positively identify the values. Standard playing cards dimensions are B8 according to ISO216 standard, which is 62 mm x 88 mm. So, we need the 88 mm card length to be covered with at least 50 pixels for proper identification.

This means around 550 pix/m (1000 mm / 88 mm = 11 => 50 pix x 11 = 550 pix/m) should be sufficient for playing cards. We may require slightly better pixel density for identifying money, since notes size is typically larger than playing cards, so if one takes the Face Inspection pixels density of 1000 pix/m, it should attain pretty good identification, although as it can be seen from the real life example below, even 770 pix/m might be sufficient. Playing cards and money shown above with 770 pix/m As it can be concluded from the above examples, the pixel density can be defined for any object and any camera, large or small. The beauty of the pixel density parameter is, as said at the very beginning, that includes all parameters influencing the clarity of the observed objects. For this reason, ViDi Labs has developed the ViDiLabs iOS calc (search the iTunes App Store under ViDiLabs calc ), a unique tool for the surveillance industry, which can also be used in cinematography, photography and any other imaging application dealing with objects details. So the following table can be used as a rough guide for various pixel densities. Free Download: The key to mitigating cybersecurity risks Exploiting IoT technology without creating cybersecurity vulnerabilities is one of the defining challenges in today s security landscape.

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PIXEL TW-283/E3 LCD Wireless Shutter Remote with E3 Type Terminal for Canon EOS 60D, E0S70D @ securityblogs.co.uk

PIXEL TW-283/E3 LCD Wireless Shutter Remote with E3 Type Terminal for Canon EOS 60D, E0S70D


List Price
£18.50

Value Price
£18.50


  • 1. Anti-vibration: With wired or wireless remote control, it can avoid damaging image integrity and quality caused by camera vibration when you press camera shutter button.
  • 2. FSK 2.4GHz Wireless Control System: It features no directionality, 80M+ remote distance and ultra-powerful anti-interference caused by other similar devices. Using international 2.4G transmission technology, it’s stable and quick response to shutter.
  • 3. Wired/wireless 4 in 1 Function: Pixel wireless timer remote control integrates wireless/wired timer, wireless/wired shutter functions, providing you a variety of choices. When the receiver is powered-off, you can use wired mode to capture the wonderful moments.
  • 4. Low-consumption LCD Screen: We uses low-consumption LCD panel to reduce its power consumption and extend working time greatly. Both of the transmitter and receiver communication channel adopt LCD screen display, which enables all the information to be displayed on the screen. So it’s easy and clear to handle.
  • 5. Aesthetic Style and Good Hand-feel: The remote control integrates aesthetic design to provide you the most comfortable hand-feel through hand-holding ratio measurement. The size is suitable for most of photographers’ hand, so it’s much handier. With high-quality leather-like anti-drop design, it offers you better tactile appeal.

Specifications:
System Mode: FSK 2.4GHz wireless control system
Transmission Distance: over 80M
Communication Channel: 30 channels
Transmitting Power: -1dB
Receiving Sensitivity: -99dB
Control Cable Length: 30cm (straight line)
Transmitter Stand-by Time: over 1000hrs. (use 2 size AAA alkaline batteries)
Receiver Stand-by Time: over 400 hrs (use 2 size AAA alkaline batteries)
Transmitter Dimension(L¡ÑW¡ÑH): :146mmX40mmX19mm
Receiver Dimension (L¡ÑW¡ÑH): 73mmX38mmX31mm
Weight: (excluding batteries)
Transmitter:52.6g
Receiver:36.2g

Shutter Functions:
Single Shooting
BULB Shooting
Delay Shooting

Timer Functions:
Timer Schedule Delay
Timer Schedule Exposure Time
Timer Shooting Number of Shots
Repeat Timer Schedule Interval Time
Repeat Timer Schedule Times

Item Included:
TW-283 Transmitter X 1
TW-283 Receiver X 1
Shutter Connecting Cable X 1
User Manual X 1

Compatible cameras: select by socket
E3 Canon EOS:Elan series, Digital Rebel (300D), XT (350D),XTi (400D), XSi (450D), T1i (500D), T2i (550D), T3 (1100D),T3i (600D), T4i (650D), T5 (1200D), T5i (700D), T6i (750D),T6s (760D),SL1 (100D) and XS (1000D),60D,70D
PowerShot:G10,G11,G12,G15,G16,G1 X,G1 X Mark II, SX50 HS
Contax:N and 645
Fujifilm:X-E2 and X-T1
Hasselblad:H series
Pentax:K10D,K20D,K100D,K110D,K200D,K-3,K-5,K-5 II,K-7,K30,K-50,K-500,*istDS,DS2,DS,DL2,DL,and D
Samsung:NX10,NX100;GX-1S,GX-1L,GX-10,GX-20
Sigma:SD1,SD9,SD10,SD14,SD15.
Note: package no include batteries.


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Aiptek Picasso DVB-T II Digital Photo Frame for Watching Free Digital Television – 7 inch (800 x 480 Pixel) @ securityblogs.co.uk

Aiptek Picasso DVB-T II Digital Photo Frame for Watching Free Digital Television – 7 inch (800 x 480 Pixel)


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Portable Digital TV and portable 7-inch 800×480 pixel digital photo frame for: Enjoying photo slide show (up to 12 megapixels) Watching free digital television(DVB-T) TV anywhere Playing back movie Listening to MP3 music Slim and simplicity design with only 18 mm in thickness and 395g in weight Embedded Li-Ion battery supports at least 3-hour slide show or 3-hour digital TV on a single charge Remote control for hands-free entertainment


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BoddBan® HD SPY Camera clock with Motion detection, Alarm, Design Mirror, Spy CAM , 1280x 960 pixel @ 30fps, 5 Mega pixel , Spy clock, Voice & Videos Recorder, Picture, Audio Sound, Remote Control with battery, 24 hours Video recording , Room/Store Temperature, 140° Wide View Angle, Music, Hidden Camera , Calendar – MultiFunctional Clock @ securityblogs.co.uk

BoddBan® HD SPY Camera clock with Motion detection, Alarm, Design Mirror, Spy CAM , 1280x 960 pixel @ 30fps, 5 Mega pixel , Spy clock, Voice & Videos Recorder, Picture, Audio Sound, Remote Control with battery, 24 hours Video recording , Room/Store Temperature, 140° Wide View Angle, Music, Hidden Camera , Calendar – MultiFunctional Clock


List Price
£48.99

Value Price
£48.99


  • HD video High Resolution Recording
  • High Capacity 4800mAh Battery with Working time on full charge of up to 20 hours
  • Remote controlled / Digital Mirror Clock Spy Camera / Motion detection / Ultra discreet
  • Can tell you what the room Temperature is and also can be used for Alarm
  • Camera has a viewing angle of 140 degrees

Record clearly and covertly with this Digital Mirror Clock Spy Camera, for ultra long 20 hours continuously on one charge!

This Spy Camera appears to be an innocent looking Digital Mirror Clock, but under that mirror there is a secret camera located within its case allowing you to record video as well as audio. The perfectly hidden pinhole lens and microphone make this spy gadget virtually undetectable. A remote control is also included to trap people more easily. And there is a lot more.
This comes with motion detection activated recording. By setting this mode, it will record only when movement is detected in front of the clock. This is a great function to capture videos you really need, other than to watch hours of useless video footage just to find out the real action. Further more, remember that this Spy Camera can record up to 20 hours on one charge, meaning that you will never have to stop in the middle of a mission just to recharge the camera!
This is a great spy device to start with. Put it in your office, the bathroom, or the meeting room, you will be surprised to find out what people are doing behind your back

Product Specifications
Video resolution: 1280×960 @ 30fps
Native resolution: 640 x 480
Video format: AVI
Audio format: WAV
View angle: 140 degree
Memory consumption: 40 minutes/1GB
Motion detection distance: direct 6 meters
Low illumination: 1Lux
Remote control distance: 18 meters
Recording Audio Area: 40m2
Support MicroSD: 32GB Max
Built-in MIC: yes
Motion detection: yes
Time/date: yes
Battery: 4800mAh
Working time on full charge: 20 hours
Room/Store temperature: -20 -80 degree C
Operation temperature: -10 – 60 degree
Operation humidity: 15-80% RH
OS: Windows 2000/XP/Vista and above

Package Contents
1 x Camera clock
1 x Remote control
1 x USB cable for charging
2 x Battery
1 x Driver CD
1 x English user manual


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