In Focus: Dallmeier - The “Megapixel Fallacy” In Stadium Video Security
In the realm of stadium security, ensuring comprehensive and high-quality video surveillance is paramount. The “megapixel fallacy” in stadium video security critically examines the common misconception that more megapixels equate to better image quality.
While high megapixel counts can enhance image clarity, especially during digital zooms, they are only one piece of a complex puzzle. Factors such as camera sensors, lenses, bit rate, ambient light and weather conditions play significant roles in determining overall image quality.
This article delves into the importance of pixel density, as standardised by DIN EN 62676, and explores advanced solutions like multifocal cameras that offer superior coverage and clarity, thus enhancing security operations and forensic investigations in large, dynamic environments like stadiums.
Do more megapixels mean a better image?
All cameras, including security cameras, are essentially photo cameras. The number of photos taken per second, called fps (frames per second), are viewed in sequence to create a video. Now a very widespread perception when it comes to image quality is that a video consisting of high-megapixel photos will be of “high quality”. However, megapixel is actually only one of the factors. There are many other factors that directly determine quality such as the sensor of the camera, lens, structure of the lens, bit rate, ambient light and meteorological conditions.
What really counts: representing reality
Based on the above information, if all factors other than megapixels are constant, what is the advantage of high megapixels? High megapixels can partially prevent image degradation, known as “pixelation”, when you want to digitally zoom in on an image, but image degradation cannot be avoided when zooming in on objects that are more distant.
Therefore, when planning, the focus should not be on how many megapixels the product has, but on how much pixel density it can provide at certain distances. This density can be determined by the number of pixels per meter, expressed as ppm (pixel per meter) or px/m. In simpler terms, the number of pixels that fit inside a 1-meter-wide object determines the pixel density. As you move away from the camera, the number of pixels that fit inside the object decreases at the same rate because the image of the object shrinks as it moves away from the camera or the human eye.
Minimum pixel density: DIN EN 62676 DIN EN 62676, which has become a global standard, provides recommendations and requirements for the selection, planning, installation, commissioning, maintenance and testing of Video Surveillance Systems (VSS) consisting of image capture and image processing devices for use in security applications.
Increasing the pixel density with the camera lens. Is that a solution?
Most of today’s security cameras have so called varifocal lenses, which is a lens whose focal length can be changed. With a varifocal lens, more distant objects can be magnified to increase pixel density at longer distances.
Although some manufacturers offer this as a solution for long distances, it should be remembered that a lens focused at a long distance cannot take images at close range and creates blind spots.
PTZ Camera: advantage or disadvantage?
Another solution to avoid losing pixel density on distant objects is optical zoom. Cameras known as PTZ (pan-tilt-zoom) or speed dome can provide the user with sufficient pixel density in objects, regardless of whether they are near or far, through optical zoom.
However, despite this significant advantage, the PTZ camera causes serious operational problems. To put it briefly, for a PTZ camera to provide sufficient pixel density in a remote incident, it must be directed to that area by an operator at the time of the incident. Working in some situations, this is sort of absurd in others, especially when there are multiple incidents at the same time.
For forensics, this has two major disadvantages: having to zoom in means that the operator must be aware of the incident already – and that all the circumstances which led to the incident beforehand will literally be “in the dark” (or in low resolution at least).
The second disadvantage is that all the areas that are not covered by the “zoom” will not be recorded at all or in very low resolution by some additional megapixel camera. Both will not suffice from a forensic perspective.
The only option for zooming into an area live and on record, independent of human effort, is to do it digitally.
Fulfilling the FIFA-guidelines: multiple sensors in one optical unit
Image capture technology, like all other technologies, is increasing its capability every day and breakthroughs are being made to eliminate barriers in this field. As a 21st century solution, multifocal-sensor camera products help to eliminate many of the problems mentioned in this article.
By combining multiple lenses in one optical unit, a multifocal camera can achieve the desired pixel density at any distance within the same image. In this way, digital zoom makes it possible to reach distant objects without “pixelation” and without sacrificing the camera’s field of view and coverage.
With this technology, stadium operators fulfil the requirements of the FIFA guidelines, which state: “The most advanced CCTV systems can monitor large, defined areas of the stadium bowl and facilitate retrospective zoom-ins which can be valuable when investigating incidents and identifying those involved.”
Unlimited number of operators and advantages in dynamic range
Multifocal-sensor cameras can be utilised theoretically by an unlimited number of users without interfering with each other, while a PTZ camera can only be controlled by one person at a time. And there is more – while a single-sensor megapixel camera has to apply light enhancement technologies to the entire image, a multifocal-sensor camera will provide optimum dynamic range for each individual sensor, massively increasing image quality in areas with different brightness.
Lower cost, more security, better investigative results
To summarise, multifocal-sensor cameras can provide the exact minimum pixel density required and provide many other operational and infrastructural benefits to stadium operators. Unlike a single-sensor camera, which offers the same megapixel resolution at every point in the photo, the plannable pixel density of a multifocal camera eliminates unnecessary high resolution that is not needed at close distances, enabling a high frames per second count and network traffic optimisation.
As the use of this technology significantly reduces the number of cameras required, it as positive cost effects on the infrastructure and labour cost while at the same time providing maximum stadium security both in live situations and in forensic evaluation after incidents have taken place.
