CCTV Test: Low Light, High Resolution
Conventional wisdom states that higher resolution cameras will always be less sensitive than devices with lower resolutions. Therefore, a number of experts and manufacturers have been quick to point out that 4K video will be beset with low light issues. Interestingly, the loudest voices seem to come from manufacturers who don’t currently have a 4K offering. Benchmark separates the fact from fiction with regard to low light performance and cameras that deliver higher resolutions.
The electronic security industry has a problem with conventional wisdom. There are self-proclaimed experts who base the credibility of their knowledge on the fact that they’ve been doing it for years so their thinking must be right. Others are clearly biased by what they sell, and cannot for one moment fathom the idea that someone else might be doing it better. There are also the audacious; a few years ago someone even pronounced themselves as the ‘IP guru’ despite not having a proven track-record working with the technology.
One issue with conventional wisdom is that some people will form strong convictions based upon little more than hearsay. The sheer volume of agreement will carry the argument.
Take bandwidth management as an example. Conventional wisdom decrees that the best way to reduce bandwidth is to lower frame rates. We’re not sure what this thinking is based on, but we’d guess at it being a throwback to the days of linear recording media and multiplexing. On the other hand, maybe those that espoused the idea had a warehouse filled with underpowered NVRs!
When Benchmark put such thinking to the test, we discovered that conventional wisdom was wrong; in real-world applications the best approach to bandwidth reduction was eliminating noise. The reality is that conventional wisdom is not necessarily true. Indeed, as technology evolves, conventional wisdom can be an obstacle to the acceptance of new thinking, theories and working practices. At times, conventional wisdom can fuel denial of new developments based on outdated thinking.
Here Benchmark does not set out to test individual devices but to challenge conventional wisdom with regard to low light performance and higher resolution cameras.
Unlike conventional wisdom with regard to bandwidth management, the conventional wisdom relating to low light performance and higher resolution cameras does actually make some sense.
Theory indicates that the low light performance of higher resolution devices will often not be as good as it is with standard definition cameras. The reason that higher resolution cameras could have inferior low light performance has to do with pixel size and density on a chip.
Image sensors require light to fall onto the pixels to create the charge which sets the relative values for each individual picture element. If you consider a D1 camera chip, it contains around 400,000 pixels. In effect, this means that the surface of the chip is divided up into 400,000 picture elements onto which enough light must fall to create a strong signal, every time a frame of video is created.
The size of the picture elements affects the low light capabilities of the camera, which is why 1/2 inch sensors are typically better performers in low light than 1/3 inch sensors.
With this in mind, consider that an HD camera has around 2 million pixels and a 4K UHD camera has over 8 million picture elements on a similar sized chip to that utilised by the D1 camera. Because the pixels are subsequently so much smaller, getting the required level of light to fall on each element can be a challenge.
The fact that higher resolution video cameras may not match standard definition cameras with regard to low light performance must be put into context: the lower resolution cameras will also struggle once light levels fall below a certain point. The need for additional illumination is not a higher resolution issue. Illuminators for video surveillance were a necessity in many applications many years before HD and UHD cameras became available.
Of course, the fundamental flaw with the theory is that it only considers chip size and pixel density. Resolution is not the only thing to have risen in recent years. Processing power has also gone through the roof, enabling the development of enhanced feature sets in the better cameras. Most credible manufacturers will include features and functions designed to enhance low light performance. These vary from the simplistic through to the complex.
It is worth bearing in mind that with any processing, every additional features does has an impact on other areas of performance. However, if the right balance is maintained, then installers and integrators can enjoy some significant benefits.
With higher resolution cameras, to ensure the delivery of compliant 4k UHD or HD streams, techniques such as frame integration or slow shutter should not be used.
Benchmark looked at cameras from four different manufacturers to assess the differences between 4K UHD cameras, HD models and a couple of D1 devices. It is worth noting that some of the lower resolution devices are no longer being manufactured. However, in their day they were considered to be good performers in terms of low light operation.
The cameras with the least difference in resolution came from Axis Communications. The P1428-E is the manufacturer’s 4K UHD bullet device. We also looked at the P1347 which has a 5MP chipset, but is typically deployed in HD1080p mode due to framerate limitations at the higher resolution. However, the chipset is the important part. While there are plenty of cameras from Axis using HD chipsets, the ones we had access to use the Lightfinder technology, which isn’t currently supported by the 4K device.
We also used the Bosch IP ultra 8000, a 4K UHD camera which was awarded Best Buy status in the recent Benchmark 4K UHD camera test. In order to consider a camera with a less dense chipset, we looked at the manufacturer’s LTC 0495, a D1 camera that was highly rated in a Benchmark low light test some five years back.
Another camera with a few years under its belt was the SHC735P, another D1 camera, this time from Hanwha Techwin (obviously back in the days when the company was Samsung). This was pitched up against an HD1080p model, the SNB6004P.
Finally, we included the Hikvision DS-2CD4185F-IZ, a 4K UHD device. This was paired with a 1.3MP DS-2CD863PF-E from the manufacturer.
Interestingly, going back to the subject of conventional wisdom, the pre-test assumption was that we’d find the older cameras – and expecially the D1 analogue units – to be superior performers as light levels fell. The feeling was that jumping from 400,000 pixels to 8 million pixels would be too significant in terms of low light performance.
Configurations obviously differed, and in some cases were limited due to the age of the devices. However, optimisation was very much geared towards enhanced low light performance. All cameras without fixed optics were tested with Fujinon lenses. The cameras were tested via a VMS, with the D1 models using a video server.
Essentially, everything that could be done to ensure the cleanest low light colour images was done. For the test, the images needed to be usable and without obvious degradation due to low light or noise.
Neither of the Axis camera used the manufacturer’s Lightfinder technology, and with that in mind the performance of both was impressive. The two devices were very close in terms of performance, and expectations are that once the technology finds its way onto a 4K unit we’ll see a drop in the light requirement.
The P1428-E did need a bit of fettling to keep noise at bay and there was some debate about the impact of the reduction processing. However, at no point did the image become unusable before light levels hit three lux.
The Bosch cameras were surprising, in that we did expect the 4K Dinion to struggle against the LTC 0495. The D1 camera was one of the better low light performers back in the days when composite video ruled the roost, and our borrowed sample still performed well.
Bosch has done a very good job with processing in the ultra 8000. The camera is feature-rich, delivers very impressive images and can still put in a good show in terms of low light performance.
Of the two cameras from Hanwha Techwin, one was very much a Samsung product. The SHC735 carried a price premium in its day, and that paid for enhanced processing back when some cameras struggled with additional features and functions. Despite this and its less dense chipset, the more modern HD1080p still delivered better low light performance. It was close, but the increased processing power of the SNB-6004 shone through. The WiseNet III platform is no slouch when it comes to low light and noise reduction, and this showed.
Finally, the Hikvision DS-2CD4185F-IZ camera has seen the manufacturer making the most of spare processing by adding a host of features and functions, including the ability to deliver clean images in low light applications. The camera does benefit from a larger imaging sensor than the other 4K models, which goes some way to boosting low light performance, but pixel density is still high in when compared with the 1.3MP camera tested alongside it.
Interestingly, last time Benchmark challenged conventional wisdom, conventional wisdom was proven to be incorrect. Again that’s the case. While the theory about pixel density bears true, what it doesn’t do is factor in the increased processing power of today’s devices, and how manufacturers have exploited that.
Benchmark carries out low light tests every year, and until 2015 we saw figures slowly creeping lower, but not getting close to the quoted specifications in real-world applications. Last year, however, we saw a significant change in general levels of low light performance. This coincided with the introduction of the new generation processing chips.
In every case, the higher resolution cameras outperformed the lower resolution models. Admittedly at times it was close, but given the increased pixel density of the higher resolution cameras, that’s still impressive. Considering that many 4K UHD cameras are still in their infancy in terms of R&D, the future is looking brighter, in more ways than one!