How Security Cameras Get Good Images In Bad Lighting
Ask any photographer what the most important part of capturing an image is, and they’ll likely tell you: lighting.
Nothing can ruin a photo or video more quickly than bad lighting and shooting in low-light situations has been challenging even the best of photographers for decades. Cameras (whether security cameras or your typical digital camera) are simply not as sensitive to light as the human eye, and require far more lumens to get a clear image. While you can see fine in a dimly-lit garage, the camera most likely can’t.
When it comes to security cameras, thankfully, technology has taken large strides in recent years to overcome this; manufacturers and technology providers are continually coming up with new technologies and camera sensors with improved light sensitivity, and high-end security cameras can now be expected to produce well-lit, clear, colorful images, in a wide variety of challenging light situations.
How are they doing this? Keep reading to find out.
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How Cameras See Light And Images
All digital cameras (security and otherwise) work in virtually the same way; the sensor captures the light coming through the lens to create an image of the scene in front of the lens. How much light is let in (or not let in) is dictated by the shutter, which opens and closes to create a small opening called the aperture. Aperture is an extremely important term in traditional photography, and for security cameras as well; the wider the aperture, the more light is let into the camera and the brighter and clearer the image. The smaller the aperture, the less light and the darker the image.
(To make things more complicated, aperture is measured in F-stops, which are inversely labeled. A wide aperture say F2.8, has a smaller number than a small aperture, like F16).
When choosing a lens for low-light situations, it’s thus best to look for the widest possible aperture; in the majority of cases, this is F1.4 or F1.8. The wider the lens, the more light will be let in – and the clearer your images in dark situations.
Low Light Technologies and Processing
While choosing a lens with a wide aperture is the first step in ensuring good images in dark scenes, it often isn’t enough for many situations – such as those with a wide dynamic range. Dynamic range is the difference in light between the light and dark part of a scene, and a scene with drastically wide dynamic range (say, looking from inside a parking garage outside onto a brightly lit day) will be difficult for a camera to accurately reproduce; most cameras just do not have the lighting capabilities.
To overcome these situations, however, security technology companies and camera manufacturers have engineered a variety of processing technologies and algorithms that can dramatically enhance the quality of images in low-light situations.
Processing algorithms are now capable of identifying different exposures in a single scene, combining them into one image, and then applying contrast enhancements, reducing noise and artifacts, and in some cases, even smoothening and sharpening pixels. By doing so, they are now capable of creating an enhanced, much-clearer image with less difference between over-exposed and under-exposed sections. Employing such powerful processing and image toning, in conjunction with a wide aperture and slower shutter speed, can allow cameras to shoot in poorly-lit situations between .02 and .1 lux – previously unheard of
These technologies can play a large role in improving surveillance and security in a wide variety of applications. Cameras can be placed near doors and windows and be able to see clearly both inside and outside, creating clear, colorful images of happenings around the facility. Warehouses and factories with loading docks and dim areas, as well as parking garages, are just a few applicable uses.
When it comes to complete darkness, however, even enhanced algorithms and wide apertures won’t save your surveillance footage. IR cameras might be necessary.
IR (infrared) cameras work differently from regular digital security cameras. While they still have the usual sensor and image, they also have an IR cut filter, which blocks out infrared light for a clear image during the day, but moves out of the way at night, allowing IR light to enter the lens and sensor, creating those classic infrared images of even total darkness. Most of the time, this image will be monochromatic, though some more-powerful image processing algorithms can combine an IR image with a regular one for color images.
IR cameras can usually capture images in as little as .1 lux. Combined with some of the increases in processing technology, some top-of-the-line IR cameras can now create daylight-looking images in situations with half that light. Keep in mind that IR cameras are different from thermal imaging cameras, which search for heat and not light or color; thermal cameras cannot create color images.
Positioning Is Also Important
While new processing firmware and powerful cameras are making a huge difference in the quality low-light images, proper placement and positioning of your cameras is also very important. If placed outside, there will likely be lights nearby, providing needed illumination – but be sure that those lights aren’t overpowering the camera sensor and making its job even harder. Bright lights can wash out the image, create unnecessary work for the image processor, and even cause flare.
A good tip: think like a photographer. Try to position your camera not only to capture what’s important on the scene, but also facing with the light, and not against. This will avoid unnecessarily backlighting the scene and creating lens flares.