To 4K or not to 4K video or Ultra HD
Our industry’s seemingly insatiable appetite for more and more
resolution has now produced a wave of interest in 4K cameras that promise
exceptional clarity and sharpness, akin to the big screen, Ultra HD television
sets found in consumer electronics stores and an increasing number of North
American homes.
The jury is still out on whether there is an immediate need for
the resolution that can overcome the downsides of increased storage and
bandwidth required for running 4K cameras in a surveillance operation. Like so
many things, if the cost of the camera, cost of the supporting system
infrastructure and components were of no concern, this new format would likely
be a more viable and attractive option for many security applications.
Here are four things to consider before making the leap to
investing in and deploying 4K video:
1.
What will I get with 4K that is not possible at lower resolution?
There’s no
doubt that 4K technology is light years ahead of analog quality, but the
reality is that the increased clarity and sharpness provided by that level of
resolution is often over and beyond what is required and able to be managed by
a typical security operation. For many reasons, full HD/1080P is the most
commonly used resolution for new systems. The majority of security systems in
use for live monitoring situation do not really benefit from such a resolution,
as the human eye is well served with the details of a 1080P picture. Higher
resolutions pay out when more details are required in forensic investigations.
2.
Double the resolution, double the processing requirements
Users
typically want to see more than one camera on one monitor, and only
occasionally switch to full screen modes. With 4K, the clarity of that
multi camera view would be no clearer than what would be viewed from a lower resolution
camera. In addition, delivering streams from multiple 4K cameras presents some
technical challenges. The client PC and graphics card must handle a significant
flow of data. The best approach is to have the live view limited to only enough
resolution for the video size and screen resolution of the display.
3.
Limitations on form factors, lenses
The
availability of affordable high resolution optics is just not there yet, and a
dome style camera with a typical curved dome bubble cannot transmit the 4K
resolution. In addition, a true 8MP resolution lens with appropriate coverage
for the 4K sensor is quite large, which would render a 4K version of the
compact dome camera (the market’s favorite form factor) essentially not
possible. The dome camera would get physically bigger which, for many
customers, is a negative.
4.
Bandwidth and storage requirements
From a cost
perspective, quadrupling the resolution from full HD to 4K won’t quite double
the camera price. However, on the recording side it will most definitely demand
more than double the storage requirements when operating under the same conditions.
So where does this leave you, 4K today or not just yet? For some
customers a bigger number is frequently perceived as a better solution but
surveillance installations should focus on the reason the system investment is
being made in the first place; protection of personnel and protection of
assets. It is far from a one size fits all decision and resolution is an
important tool in the system solution.
Next benchmark for video surveillance cameras
is going to be the Ultra HD standard, with a resolution of 3840 x 2160 –
around 8MP. Given the challenges networks may face carrying Ultra HD video
streams it’s hard to say just when we will see the technology reach a tipping
point.
THERE are a
couple of signs worth paying attention to with Ultra HD (commonly called 4K in
consumer and CCTV industries). The first is that UHD consumer monitors, which
are now dropping in price at a time many homeowners’ first 1080p HD monitors
may be starting to look a little tired. Something else to bear in mind is the
consensus forming in digital photography that 8MP is the sweet spot that allows
the best balance of low light performance and high resolution.
As most
readers know, the more pixels you cram onto an imager, the smaller those pixels
must be. And the smaller the pixels, the less light they can absorb. Double the
number of pixels on a 1/3-inch HD sensor and you halve the light reaching the
sensor. The result is that more pixels does not a perfect camera make – not
unless sensor sizes increase. If it’s all about display images today, then 3MP
cameras with a 1080p resolution are ideal.
But if you
need digital zoom or you use a UHD monitor, then Ultra HD cameras should be a
consideration. If you zoom in 2x digital with an Ultra HD image then you are
viewing at 2MP, which is pretty good considering how quickly it takes an HD
camera to burrow down under 4CIF when digital zoom is applied.
Something
else to bear in mind when considering digital image quality is that pixels on a
digital camera’s sensor capture light in red, blue or green – not all colours
at once. A layout will be a pair of green, a red and a blue in a grid pattern
and onboard software then nuts out the colour value for pixels. This means
there’s signal attenuating averaging going on in the background - one colour
per 4 pixels.
A camera’s
digital engine is also working hard to stave off false colours and moire –
spacial aliasing that causes false patterns in a scene. Camera engines will
blur an image slightly then sharpen it in order to lose such artifacts.
Clearly, the more pixels, the more work the camera processor has to get through
and this can be noticeable as latency or blurring if there’s sudden movement –
like cars moving at right angles across a scene.
Lenses are
another issue. An Ultra HD camera is going to need a quality lens and there’s
no doubt that plenty of 1080p cameras are being sold with lenses that are not
perfect. Sure, things look good in the centre of the image but out towards the
edges details get muddy, especially on the sorts of deep zooms that might
motivate a buyer to choose Ultra HD in the first place.
Sensor noise
is also something that has to be considered at multiple levels. In low light,
cameras increase exposure, elevating noise levels. Furthermore, pixel
measurements are never perfect and the flaws in these signals show up on a
monitor as noise. It’s unhelpful during the day and blinding at night. Digital
noise reduction is the answer but DNR processing doesn’t just lose noise, it
sloughs fine detail off a scene. When you look at a camera being tested in low
light you can often see the areas where DNR has scrubbed and smudged a scene
free of detail. It’s not a good look.
Engineers
can build high resolution imagers with fewer noise problems but they need to be
big – 1-inch or 1/1.5 inch sensors are ideal. A 1/1.5-inch sensor has 4x the
area of the 1/3-inch sensors that typically run inside 1080p CCTV cameras. No
wonder GBO’s S1080 camera (BGWT sells them in Australia) with its monster
1-inch sensor has such a great image in low light.
If the
sensors are large enough, the lenses are good enough, the network is capable
enough and the storage sufficient, then Ultra HD cameras will give end users a
lot more detail than 3MP 1080p cameras can. But this capability has to be
balanced against many things. Image quality is about more than megapixel count.
“If a sensor is of the similar size as the
equivalent HD sensor and it has 4x the pixels - low light performance will be
4x lower. And streaming bandwidth will be close to 4x larger unless better
compression is used”
Keep in mind,
4K = 8.3 megapixels, aspect ratio 16:9
Horizontal resolution
1080p= 2.1 megapixel, aspect ratio 16:9
Vertical resolution
720p= 1.3 megapixel, aspect ratio 16:9
Vertical resolution
D1= 0.4 megapixel, aspect ratio 4:3
Vertical resolution
