For applications at the very bottom of the low-light range, look for a camera that supplies its own IR illumination.
2. Digital Slow Shutter
This is a feature where the camera’s electronic shutter is slowed to below normal speed to allow additional light to be captured by the sensor. It works very well in improving low-light performance but has some side effects including image noise and a potential to blur moving objects.
If a camera has this feature, it is important to see how well it was implemented, as not all executions of slow shutter are equal. Besides the noise and blur, be on the lookout for how quickly the camera reacts to large or fast-changing light levels, and how well it recovers and settles. A poor implementation can yield a complete loss of usable video for 5 to 10 seconds while the camera tries to recover to a proper exposure level.
More of the slow shutter is not always better. We have found in scenes that include motion anything slower than 1/3 to 1/4 of a second starts to be counterproductive due to image blur. At 1/2 second someone can actually run through the scene and not be seen.
3. Digital Noise Reduction (DNR)
This is a feature that can help improve a low-light image by removing (or masking) some of the luminance and chroma noise present in a low-light image. It does not actually help increase low-light sensitivity like some of the other features mentioned, but it can improve object recognition and help reduce encoder, bandwidth and storage needs. This, too, can have adverse side effects on moving objects like image smear, image softening and even image stutter. As with slow shutter, not all implementations are equal so it is recommended to compare cameras and evaluate overall benefit vs. side effects. Users should also pay attention to whether DNR affects performance in bright lighting, as it should not.
4. Tinted Bubbles
This is an obvious but often overlooked item when projects are bid. Many cameras today are shipping in mini-dome configurations that include a housing and protective bubble. If low-light performance is paramount for certain locations, try to make sure tinted or smoked bubbles are not used. Depending on materials, they can be 1 to 2 f-stops darker than a clear bubble. For every f-stop, half of the total light is lost. This means the amount of light getting to the sensor would be reduced by 50 percent (1 f-stop) to 75 percent (2 f-stops) just because of the bubble.
2. High Profile H.264 compression
There are multiple profiles of H.264 and users should be wary of which profile a manufacturer uses. High profile is generally more processor intensive and is a bit harder for a manufacturer to deliver well,but the result is worth the development effort.
Buyers should be aware of the base profile H.264 implementations. While high profile is used for media such as Blu-ray, base profile is used for applications like teleconferencing. The image quality standards between those two profiles speak for themselves.
If you are concerned about low-light performance, line up the camera options where they are intended to be used and test them against each other. Camera shoot-outs should be the norm for end-users who care about image quality in any conditions, and this is especially true for low-light applications.
At the end of the day, this is the best way to ensure that the best technology will be chosen for the application.