Megapixel Video for. Part 1 of 4. Brought to You by. Presented by Video Security Consultants

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1 Megapixel Video for Brought to You by 2009 Video Security Consultants Presented by Part 1 of 4 MARCH 2009 A1

2 Megapixel Video for Part 1 of 4 Making the Most of Megapixel s Marvels Gang way, the Megapixel Revolution is upon us! No, it s not the latest Transformer movie blockbuster but rather the coined phrase signifying the arrival of superior video surveillance technology. This, the first of a four-part series, has been designed to transform you into an expert on the topic. By Bob Wimmer Welcome to Part I of the latest in SECURITY SALES & INTEGRATION s acclaimed D.U.M.I.E.S. series: Megapixel Video for D.U.M.I.E.S. Brought to you by Pelco, this four-part series has been designed to educate readers about megapixel cameras and video the next phase of surveillance technology following the leap from digital to IP-based, or networked, CCTV systems. D.U.M.I.E.S. stands for dealers, users, managers, installers, engineers and salespeople. Recently, the Megapixel Revolution has begun to affect all of us in the industry. First came the megapixel camera, then megapixel lenses and, of course, megapixel video recorders. Perhaps the megapixel coffee cup is next! It s for certain that this changing technology is on a very fast track, and a great deal of hype has surrounded the megapixel revolution. But what exactly is this so-called revolution all about? What is required to support megapixel systems and what are the main advantages of megapixel and IP cameras over analog cameras? The answers lie in this series of articles, which will cover the theoretical and practical technology and design theories required to intelligently sell, install or service megapixel solutions. A2 MARCH 2009 Advantages of Megapixel Cameras Anyone following the megapixel movement has already heard the three main advantages for the incorporation of megapixel technology: 1. better image quality; 2. fewer cameras required; and 3. virtual pan/tilt/zoom (p/t/z). Let s take a closer look.

Better image quality The most noticeable advantage of megapixel cameras is image quality. In some cases, this advantage can be confusing or even misunderstood.

1-megapixel camera can appear to have the same image quality when viewed on a standard monitor (see page A7 for more on image resolutions).

3 Better image quality The most noticeable advantage of megapixel cameras is image quality. In some cases, this advantage can be confusing or even misunderstood. For example, comparing a standard high-resolution analog output camera producing 580 TVL and a 3.1-megapixel camera can appear to have the same image quality when viewed on a standard monitor (see page A7 for more on image resolutions). The real test is in the ability to zoom or focus on just a small area of that scene this is where the megapixel camera will prove to be superior (see diagram right). Analog Vs. Megapixel Image Quality 580TVL Camera 3.1-Megapixel Camera Fewer cameras required When outfitted with high quality wide-angle lenses, megapixel cameras have the ability to cover a much wider area than analog CCTV cameras. It has been stated, Comparing apples to apples, a 1-megapixel camera can cover more than four times the area of a standard CCTV camera with the same resolution. This means you can replace four CCTV cameras with a single megapixel camera. How can one camera replace a total of four standard cameras? The answer is all four would have to be in the same general area (see diagram below). The statement means that when using a very wide-angle lens, a megapixel camera can electronically divide that area into four parts and display each of those sections with the same high quality as if using three or four cameras. Wide-Angle Megapixel Camera Coverage Photos courtesy Theia Technologies Electronic Zoom Zoomed-in images One of the top three advantages of megapixel technology is better image quality. Here one can see the clarity rendered by the megapixel camera (right) is considerably sharper than its analog counterpart. These differences become quite apparent when zooming in. Equipping megapixel cameras with wideangle lenses can enable them to cover four times the field of view as conventional analog cameras while maintaining the same level of resolution. Ultimately this means fewer cameras could be required to perform the same surveillance task. Virtual p/t/z Another advantage of megapixel cameras is the application of virtual p/t/z, which stems from similar capabilities to the aforementioned multicamera example. Instead of displaying three or four cameras on individual screens, the pixels within the camera sensor are actually addressed in such a way that it appears the camera is moving around a scene. The main consideration of both the multicamera description and virtual p/t/z is the quality of the lens incorporated into the megapixel system. The characteristics of megapixel lenses will be addressed later in this article. An additional advantage of megapixel technology is video compression and the reduction related to cable costs and the use of existing cable in system backbones. Bandwidth is a main limitation for megapixel cameras. Due to the structure of the NTSC standard, bandwidth was restricted and, therefore, the need for IP-addressable cameras as well as video compression is an issue. This will be further detailed in Part II of this series, but, as an example, a 3.1-megapixel camera without compression would require approximate- MARCH 2009 A3

Megapixel Video for Virtual Pan/Tilt/Zoom in Action Megapixel cameras have the ability to allow users to zoom-in to different areas within a field of view during either live or even recorded video

4 Megapixel Video for Virtual Pan/Tilt/Zoom in Action Megapixel cameras have the ability to allow users to zoom-in to different areas within a field of view during either live or even recorded video surveillance. This capability is referred to as virtual pan/tilt/zoom (p/t/z) and is considered one of megapixel technology s leading advantages. ly 168MB bandwidth. IT personnel would not exactly be enamored with that type of camera being inserted onto their networks. In summary, megapixel technology offers many improved features for the surveillance industry such as better image quality, electronic zoom and virtual p/t/z systems. Are these sufficient enough to offset the high price of equipment? It depends on the particular application, how shrewdly these advantages are deployed, and how the return on investment (ROI) and total cost of ownership (TCO) results are calculated. Sometimes, more money spent now can mean savings down the line for the end user. It s for sure that megapixel technology has a place in the security industry, but only time will tell the full measure of its ultimate impact. CMOS Image Sensors Come of Age What changes to camera technology have led to the megapixel revolution? The first and foremost advancement is the camera sensor. Through the years the sensor has gone through many stages of increased performance. The early sensors incorporated in surveillance cameras consisted of either CCD or CMOS chips. CCD Vs. CMOS Camera Sensors CCD CMOS Noise moderate moderate Processing sensor sensor Dynamic Range wide wide Sensor Output analog digital A key difference between charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS) camera chips is the latter outputs its information in a digital format. While CCD has dominated the video surveillance sector, IP and megapixel cameras are helping CMOS encroach on the marketplace. CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) image sensors are two different technologies for capturing images digitally. Each has unique strengths and weaknesses that lend advantages in different applications. For a long time, CCD has been the most popular choice for video surveillance use. But during the past five years much has changed with both technologies, and the current situation seems to favor the CMOS sensor. Both types of imagers convert light into electric charge and process it into electronic signals. In a CCD sensor, every pixel s charge is transferred through a very limited number of output nodes to be converted to voltage, buffered and sent off-chip as an analog signal. All of the pixel can be devoted to light capture, and the output s uniformity (a key factor in image quality) is high. In a CMOS sensor, each pixel has its own charge-to-voltage conversion, and the sensor often also includes amplifiers, noise-correction and digitization circuits, so that the chip outputs digital bits. These other functions increase the design complexity and reduce the area available for light capture. With each pixel doing its own conversion, uniformity is lower. But the chip can be built to require less off-chip circuitry for basic operation. The main reason for the success of the CCD over the CMOS in the early stages of video surveillance was the lower noise, less video smearing and blooming found in CMOS devices. However, with the increased performance of CMOS devices and the fact that it is truly a digital output and requires less power to operate, CMOS chips have become the choice for IP and megapixels cameras. The main advantages of today s CMOS devices include: System-on-a-chip integration allows smaller cameras Lower cost of sensor chip and fewer components in camera Easy digital interface for faster cam- Much lower power era design applications Less image artifacts no blooming or smear, with same sensitivity Higher dynamic range for security Digital output for faster readout speeds and frame rates Direct addressing of pixels allows electronic p/t/z A4 MARCH 2009

For Pixels, It s Hip to Be Square Analog CCTV systems typically have nonsquare pixels for the sensor to meet NTSC/PAL standards and display properly on 4:3 monitors.

Older CCTV cameras had a nonsquare 4.8 X 3.75 micron pixel size, with only a 70-percent fill factor. The sensors incorporated in megapixel cameras have square pixels ranging from 1.8 (H) X 1.

Fill factor is the ratio of light on a given area that is collected by the silicon and turned into signal, divided by the total area of the pixel.

5 For Pixels, It s Hip to Be Square Analog CCTV systems typically have nonsquare pixels for the sensor to meet NTSC/PAL standards and display properly on 4:3 monitors. However, almost all digital megapixel cameras use square pixels. The advantage of square pixels is light collection efficiency. Square pixels maximize the fill factor for a given pixel pitch. Older CCTV cameras had a nonsquare 4.8 X 3.75 micron pixel size, with only a 70-percent fill factor. The sensors incorporated in megapixel cameras have square pixels ranging from 1.8 (H) X 1.8 (V) microns to 2.2 (H) X 2.2 microns (V). The pixels are square and the fill-factor is close to 90 percent. Fill factor is the ratio of light on a given area that is collected by the silicon and turned into signal, divided by the total area of the pixel. That means 90 percent of the photons incident into the square area are converted into signal. In other words, square pixel sensors offer greater overall camera sensitivity. Ever wonder why, when reading camera specification sheets, you would see two sets of numbers rating the sensor of the camera? One lists the number of pixels (768 H X 494 V) for the sensor and the other rates the horizontal resolution (TVL) of the camera. Observe SPECIFICATIONS: (Camera) Effective pixels (Horizontal) X 494 (Vertical) Horizontal resolution TV lines Interlace Scanning Display Technology This confusion is caused by the difference between pixel aspect ratio and picture aspect ratio. The latter is the ratio of the image s width and height. Due to nonsquareness of pixels in standard-definition TV, there are two types of picture aspect ratio: storage aspect ratio and display aspect ratio. The former is the ratio of the image s width to height in pixels, and can easily be calculated from the video file. Display aspect is the ratio of image width to height when displayed on screen, and is calculated from the combination of pixel aspect and storage aspect ratios. This explains why a 768 horizontal sensor when displayed on a 4:3 aspect monitor will result in only 540 TV lines of spatial resolution. Some video-editing software applications often ask users to specify an aspect ratio for their video file, presenting the choices of 4:3 and 16:9. In such situations, the video-editing program is implicitly seeking the pixel aspect ratio of the video file by asking for information about the video system from which the video file originated. One field of video information = scan lines ODD field = lines 1, 3, 5, 7, etc. EVEN field = lines 2, 4, 6, 8, etc. Two fields = 1 Frame Interlace scanning is a video display technique that uses two fields to create a frame. One field contains all the odd lines in the image; the other contains all the even lines. The slight delay between odd and even line refreshes creates some distortion or jaggedness. Role of Progressive Scanning Interlaced scanning has served the analog camera, television and VHS video world very well for many years, and is still suitable for certain applications. Interlaced scan refers to one of two common methods for painting a video image on an electronic display screen by scanning or displaying each line or row of pixels. This technique uses two fields to create a frame. One field contains all the odd lines in the image; the other contains all the even lines. The slight delay between odd and even line refreshes creates some distortion or jaggedness. This is because only half the lines keep up with the moving image while the other half waits to be refreshed. However, now that display technology is changing with the advent of liquid Progressive Vs. Interlaced Scanning Interlaced Scan Progressive Scan As opposed to interlaced scanning, progressive scanning (right) scans the entire picture, line by line, every 16th of a second. In other words, captured images are not split into separate fields as they are in interlaced scanning, resulting in virtually no flickering effect. This makes it well suited to surveillance applications. MARCH 2009 A5

Megapixel Video for crystal displays (LCD), thin film transistor (TFT)-based monitors, DVDs and digital cameras, an alternative method of bringing the image to the screen, known as progressive

In other words, captured images are not split into separate fields as they are in interlaced scanning. Computer monitors do not need interlace to show the picture on the screen.

As such, in a surveillance application, it can be critical in viewing detail within a moving image, such as a person running away.

Some systems may incorporate what is known as de-interlacing, which can somewhat compensate for the effects of interlacing.

6 Megapixel Video for crystal displays (LCD), thin film transistor (TFT)-based monitors, DVDs and digital cameras, an alternative method of bringing the image to the screen, known as progressive scanning, has been created. Progressive scanning, as opposed to interlaced, scans the entire picture, line by line, every 16th of a second. In other words, captured images are not split into separate fields as they are in interlaced scanning. Computer monitors do not need interlace to show the picture on the screen. It puts them on one line at a time in perfect order (e.g. 1, 2, 3, 4, 5, 6, 7, etc.) so there is virtually no flickering effect. As such, in a surveillance application, it can be critical in viewing detail within a moving image, such as a person running away. However, a high-quality monitor is required to get the best out of this type of scan. Some systems may incorporate what is known as de-interlacing, which can somewhat compensate for the effects of interlacing. De-interlacing is the process of converting interlaced video into a noninterlaced form, eliminating some jaggedness from the video for better viewing. This process is also called line doubling. Some network video products integrate a de-interlace filter that improves image quality in the highest resolution (4CIF). This feature eliminates the motion blur problems caused by the analog video signal from the analog camera. In sum, specific advantages of progressive scan compared to interlacing include: Higher vertical resolution than interlaced video with the same frame rate Absence of visual artifacts associated with interlaced video of the same line rate, such as interline twitter As we move away from the old scan standards we can also improve the image quality in megapixel devices. As you may recall, the old NTSC standards allowed for 525 scan lines per image. As the new high-definition standard is being incorporated, megapixel cameras can also offer more rows of scanned information. The newer design allows for 720 to 1,080 rows of vertical information. This increase of information adds to the overall performance of megapixel cameras. Megapixel s Specialized Lenses What would a Megapixel camera be without a megapixel lens? Megapixel lenses are not new to the camera industry. Anyone familiar with machine vision optics will completely understand megapixel lens theory. Today s megapixel cameras have many advantages as long as you have the right lens for the job. If your application calls for covering large areas or reducing overall system costs by installing fewer cameras, the lens of choice should be wide angle. Until recently, only fisheye lenses were available for an ultra-wide field of view. Eliminating Wide-Angle Distortion Fisheye lenses create a curved and distorted image that no one seems to like. This significant distortion causes loss of resolution at the image edges. In recent years, a newly designed rectilinear lens has become available that gives a different ultra-wide view without the barrel distortion or loss of edge resolution of fisheye lenses. Because distortion correction is done optically in the lens, no additional dewarping software or hardware is required. Images appear more natural and have greater resolution, which is a major requirement for megapixel cameras. Ultra-wide angles are not the only characteristic found in megapixels lenses. The ability to focus light on smaller areas of the sensor and how well the lens can pass different frequencies also are very important. Many people rate lenses just by the f-stop a measure of how well the lens passes light. It is a ratio of the focal length of the lens (in millimeters) to the diameter of the iris opening. Megapixel lens: 0.3% Standard lens: 13% New rectilinear lenses (left) provide ultra-wide-angle views without the barrel distortion or loss of edge resolution seen with the fisheye lenses (right) of the past. As a result, images appear more natural and have greater resolution. Photos courtesy Theia Technologies A6 MARCH 2009

The smaller the number, the more light the lens will pass. Most lenses are not perfect optical systems. Light, when passing through a lens, undergoes a certain degree of degradation.

7 The smaller the number, the more light the lens will pass. Most lenses are not perfect optical systems. Light, when passing through a lens, undergoes a certain degree of degradation. Megapixel lenses must address not only resolution but also contrast. This measure of quality of lenses is known as the modulation transfer function (MTF). Let s dig a little deeper into MTF and a couple of other factors stray light and color fringes that also relate to the performance of megapixel lenses. MTF of lenses Modulation transfer function is the measure of the quality of performance of an optical system based on comparison of the contrast at a given frequency of the image projected by the system vs. the contrast of the original subject. A perfect system would project an image that has the same contrast levels as the original: real systems lose some contrast due to imperfections in lens design. This measurement is what separates normal lenses from megapixel lenses; it is also what generates the difference in costs of the lenses. Minimum levels of scattered light (stray light) Stray light manifests itself as a uniform brightness level that is superimposed on the image (useful light). This is caused by undesired reflections at the lens mountings, the diaphragm blades and the lens surfaces, and causes the dark parts of the image to appear brighter. The dynamic range (ratio of the brightest to the darkest point on the image) is thereby reduced and, of course, the contrast in the finer details as well. Good megapixel lenses should have optical systems that have a stray light ratio of less than 3 percent. Absence of color fringes Color fringes occur along light/dark or dark/ light edges, and take the form of a colored seam or line along those edges. Resolving Resolution Analog camera resolution is usually rated in TVL (TV lines) whereas the newer cameras both IP and megapixel are rated in pixels. Resolution can be measured in various ways. Basically, spatial resolution quantifies how close lines can be to each other and still be visibly resolved. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch) or to the overall size of a picture (lines per picture height, also known simply as lines, or TV lines). Another convention is to cite resolution as the total number of pixels in the image, typically given as number of megapixels. This can be calculated by multiplying pixel columns by pixel rows and dividing by 1 million. Other conventions include describing pixels per length unit or pixels per area unit, such as pixels per inch or per square inch. None of these pixel resolutions are true resolutions, but they are widely referred to as such. 117 lines 88 TVL 1.1MHz We have already become acquainted with such light/dark transitions as test patterns: they are the black/white bar grids in the sidebar image. These are reduced in the process of taking a picture, not only in their contrast but colored lines become evident as well. In this context, it is not only the expansion of the colored lines that is of significance but also the brilliance or paleness of the colors. Color fringes are an especially critical factor in wide-angle displays. Visit the Special Reports section at to access more than five years of D.U.M.I.E.S. archives. Comparing TV Lines and Pixels 140 lines 106 TVL 1.32MHz 235 lines 176 TVL 2.2MHz Spatial Resolution (TVL) 1 X 1 2 X 2 5 X 5 10 X X X X 100 Pixel Resolution (Megapixel) 352 lines 264 TVL 3.3MHz 704 lines 528 TVL 6.6MHz Resolution terminology differs depending on whether it is an analog or digital device. But whether it is the former (TVL) or the latter (pixels), the higher the number, the higher the resolution and the greater the image clarity. Next Up for DUMIES : Compression With security cameras, the convenience of plugging a camera into your existing IP network and viewing it from anywhere in the world within minutes is very exciting. However, with megapixel technology, this viewing of security cameras across any network could produce a challenge for any IP professional. The ensuing articles in this series will address the compression methods and image rates required by megapixel cameras in order to ensure an efficient network. n Robert (Bob) Wimmer is president of Video Security Consultants and has more than 35 years of experience in CCTV. His consulting firm is noted for technical training, system design, technical support and overall system troubleshooting. MARCH 2009 A7

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Megapixel Video for. Part 2 of 4. Brought to You by. Presented by Video Security Consultants

Megapixel Video for. Part 2 of 4. Brought to You by. Presented by Video Security Consultants rought to You by 2009 Video Security Consultants Presented by Part 2 of 4 A1 Part 2 of 4 How to Avert a Compression Depression Illustration by Jerry King While bandwidth is widening, larger video systems