Ask Before Buying
Not all products are created equal, so it is important to ask the right questions
- By Allen Chan
- Sep 01, 2015
There is little arguing that 4K is positioned to become the next imaging
standard in the security industry. Nearly every major camera
manufacturer today, including Sony, has a 4K offering, and large
VMS providers offer support for 4K cameras. In addition, early
adopters of 4K surveillance cameras include cities, transit operators
According to the latest market data from IHS Inc. for the Americas, revenue
from the sale of network cameras with four or more megapixels is forecast to grow
more than twice as fast as the average for the network camera category in the next
“4K will be a major driving force for the high megapixel network camera
market,” said Josh Woodhouse, senior analyst for IHS. “In a similar manner to
HDTV, end-users are expecting the same high-quality 4K compliant video from
their surveillance systems as they are seeing emerge on their consumer devices.”
Early end users are drawn to the resolution of 4K, which is four times that of
full HD, as well as 4K’s ability to increase wide area surveillance while still capturing,
magnifying and examining the smallest parts of a scene. Looking at a section
of a larger 4K image, the increased number of pixels captured means that objects
are more defined compared to a high-definition image. This makes it easier to
identify smaller details, as the content is less blurred. Higher 4K resolution also
means more accuracy. Most security applications usually require either situational
awareness or detailed monitoring of specific areas of an image, especially for postincident
analysis. With 4K, it is possible to achieve both situational awareness and
detailed monitoring at the same time.
Unfortunately, there is no standardization around how camera specifications
are written, which has been problematic in the security industry. To this day, 4K
cameras are no exception. Camera specification sheets appear to offer comparable
features across the board, but they do not tell buyers the true capabilities of a
product. For this reason, it is not enough for security professionals to simply compare
datasheets and make purchasing decisions based solely on specifications.
Purchasers need to ask manufacturers several detailed questions before deciding
which 4K cameras are actually going to meet all of their installation requirements.
Is the Lens Optimized for 4K?
Resolution, as defined by the image sensor, does not necessarily translate to the
other optics that may be included with a camera. For example, the lens also needs to be well-matched to the image sensor. Even with
the best 4K image sensor in place, the wrong lens can
limit the camera’s overall performance and inhibit the
production of 4K quality pictures.
In order to capture full 4K resolution, a camera’s
lens needs to be at least eight megapixels. However, lenses
with such high resolution are expensive; particularly
those that can support the zoom movement required for
so many security and surveillance applications.
To make their cameras more affordable, some
manufacturers use lenses that are not built for 4K imaging.
Doing so does reduce costs, but it can also degrade
resolution to the point that the camera should
no longer be classified as truly 4K. While the overall
picture may appear “good enough,” users will certainly
start to notice the difference when zooming in on
the finer details of a scene.
The physics behind this are quite complicated, but
they boil down to a few important points. Image sensor
design has evolved around the idea of smaller and
smaller pixel sizes. The smaller the pixel size, the more
of them that can fit on the senor. However, this leads
to a mismatch between the sensor resolution and the
lens. A 4K camera lens needs to employ higher optical
performance and lower F-numbers so that it can take
advantage of all the information generated by the 4K
In addition to resolution, the overall quality of
a lens is impacted by other important specifications
like the Mean Transfer Function (MTF), the F-stop
normally associated with the “speed” of the lens, and
Why is Minimum Illumination Important?
Today, most 4K cameras have poorer minimum illumination
ratings than their full HD counterparts,
meaning that they require more light to produce usable
images and will switch from color mode to black-andwhite
mode before an HD camera. This is simply because
when using similar sized imagers, the sensor area
to gather light becomes smaller as resolution increases.
As there is no standard for minimum illumination
in the security industry, it is important that the specifications
from different products be “normalized” to
a set parameter. As an example, Sony uses 50 percent
video level, with a defined set of conditions like a normal
shutter speed of 1/30 second, AGC ON, with a
lens F stop of 1.6. When the shutter speed is slowed
down by 50 percent, it results in a minimum illumination
number which is approximately two times better.
Of course, sensor sensitivity improvements are a
factor as well. Most 4K cameras still bring in light
using a front-illuminated structure. However, a backilluminated
structure can more than double the camera’s
light sensitivity characteristics. A back-illuminated
CMOS sensor will have more than two times better
sensitivity than a conventional CMOS sensor. In order
to compensate and increase gain, many 4K cameras
simply use a slower shutter speed that allows more
light to be “stored” to the image sensor. However, this
may not be ideal as any moving objects will easily become
blurry or grainy with gain being too high.
In situations where lighting is really poor, (IR) illuminators
can be deployed. The challenge when using
external IR sources is how to maintain overall picture
clarity as objects move from far to near or vice versa.
Having a built-in IR light source allows the camera to
better control the illumination level or exposure.
How Does the Camera Manage Bandwidth
When resolution goes up, bandwidth consumption
and storage needs also increase. This can make deploying
4K cameras more expensive and more challenging
than deploying full HD cameras.
Most 4K surveillance cameras today use the H.264
video coding format. This is a standard coding format
used in many kinds of video, including Blu-ray discs,
HDTV broadcasts and online streaming for sites like
YouTube. However, because 4K video contains so
much more data than full HD, using a standard method
of compression is not enough to keep bandwidth
consumption in check.
Using region of interest (ROI) coding is one way
to mitigate bandwidth and storage challenges, using
less compression and therefore better image quality
only in the important areas of the picture and only
when needed. Most of the time, only particular areas
of the video are of interest—such as a moving car or
a store entrance. ROI allows users to view enhanced
details of the relevant area while transmitting and
archiving extraneous parts of the image in a lower
Some 4K cameras can be programmed in advance
for static (still) ROI. Another way is to use dynamic
(moving) ROI, using analytics like motion detection
to determine the critical region, or a combination of
both static and dynamic. Analytics in the camera can
also be used to dynamically crop the area of interest
and stream only this region back to the head end.
For example, Sony’s use of ROI—Intelligent
Cropping—allows users to select the portions of an
image that they want to see in its native resolution.
All other parts of the image are transmitted at full
HD resolution, resulting in lower bandwidth consumption
by reducing the amount of video transmitted.
In other words, you are not transmitting in 4K if
images are cropped.
Although widespread adoption is still several years
away, 4K is already emerging as the next imaging
standard for security and surveillance applications.
Security professionals need to be armed with the right
information and the right questions to ask vendors so
that they can make the right choice
for their 4K needs today and well
into the future.
This article originally appeared in the September 2015 issue of Security Today.