If you’re thinking HD cameras are all the same, you’re wrong. Even
within a single manufacturer’s product line-up there are fundamental
variations in resolution across all possible environmental applications,
to say nothing of variations in compression and image processing.
IT would be nice to think that HD cameras were all identical – that
they conformed to a cast iron specification and we could depend on
their performance to be true in all applications. But that’s simply not
the case.
There’s
plenty to think about when it comes to choosing the best HD cameras and
in this issue we spoke to a number of different manufacturers and
commentators about the sorts of things integrators, installers and end
users should be looking for in their HD camera solutions.
First
cab off the rank is Vlado Damjanovski of C.R. Kennedy and ViDi Labs.
Damjanovski’s credentials go pretty much without saying and he has no
doubt the area of importance when it comes to HD camera selection – it’s
image quality.
“Image quality is the key and this depends firstly and foremost on the sensor
used,” Damjanovski says. “I refer here to resolution, dynamic range,
noise and speed of read-out. There are only a handful HD sensor
manufacturers in the world, and as such there wouldn’t be a big
difference when the raw image coming from an HD image sensor is
concerned.
“Instead
the big difference may come from the intelligent processing of the raw
video and its interface to the external world. And, if the signal is
compressed, how good the compression is, what level of compression is
used and what default settings are used.
“Another
very important feature is how many concurrent encoders can be used (if
more than one) for the purposes of dual or triple streaming, one for
recording, display and another perhaps for remote streaming with lower
bandwidth. Also, for larger projects how multicasting is handled might
be the next most important thing.
“Of
course, the standard installer demands are still relevant,” Damjanovski
says. “These include ease of installation (preview), PoE, mounting,
etc. This depends on the camera manufacturer, not the sensor
manufacturer. Additional factors of course are the lens quality. We all
know that if a lens is of an inferior quality (compared to the sensor
resolution), it is impossible to make the HD video any better.”
Given
the multiplicity of qualities we’ve touched on here, what specific
features should installers look for when choosing a quality HD camera?
“In
CCTV, most often it is the low light performance that might be decisive
for a lot of projects,” explains Damjanovski. “But, as many would
appreciate, the pixel size in most HD sensors is even smaller than the
analog resolution sensor, hence it will be a tough ask to get an HD
camera to outperform a good SD analog in low light.
“So
my advice to installers is to be aware of where the HD camera needs to
be installed first. HD cameras will produce better picture, there is no
doubt, but if low light performance is the most important requirement,
installers should consider additional illumination (normal or IR) to
produce better signal of HD at low light.
“Next
thing to consider is having power-over-Ethernet (PoE) to simplify
cabling, but also the HD camera sensor capability. Some manufacturers,
like Dallmeier, offers cameras with multi-formats (SD, 720, 1080, 3 MP,
4MP or 5 MP) switchable through the software.
“Certainly,
the most important of all might be the image quality, so before you
decide to invest in HD cameras, get a sample footage and check the video
quality for yourself. Even better, get various cameras and test them on
your site at the light levels typical for that site.”
So 720p or 1080p, which is best? Does improved compression mean there’s no longer a need for 720p?
“Theoretically,
more resolution is always better, but, some will argue that a 720p
sensor may have larger pixels, hence better low light performance, and
makes smaller stream, as it has half the amount of pixels (1280 x 720)
then the 1080 (1920 x 1080),” Damjanovksi says.
“But
be aware that some cameras, like the Dallmeier DF4910 range, offer a
choice of resolution in the same camera, because the sensor they use in
this camera is a 5MP sensor and it allows you to choose whatever suits
the application.
“Even
better, such a camera uses pixel-binning when in 720p mode to produce
better low light performance, so it all depends on the camera design.
The most obvious benefit of such multi-format sensor cameras is the
angle of view switching without changing the lens - when a sensor mode
is changed the angle of view changes.”
There
are lingering questions over the weaknesses of HD cameras – for
instance, how are they in low light compared to the best analogue
cameras? How are they in very strong backlight? What about white noise in low light scenes impacting on storage volumes?
“The
low light performance is very much dependant on the sensor type and
pixel size,” Damjanovski says. “A typical HD sensor pixel size would be
around 2 microns (4 square microns), and on some sensors even smaller.
As a comparison, analog sensors typical pixel size is 6 microns (36
square microns).
“In
surface area this is 9 times bigger in the SD cameras compared to the
HD. This is the most important factor defining low light performance
under the same conditions (temperature and camera processing) and
applies to majority of cameras in our industry today. But, the
technology development doesn’t stop, and we will soon see some new
inventions, like back-illuminated CMOS sensor.
“These
are used on the iPhones, and other smart phones and they will increase
low light performance without increasing the pixel size. The dynamic
range, back-light processing is directly dependant on the pixels size
too, but here too, there are some developments where double exposure is
used to simulate high dynamic range.
“As
for the storage of noisy signals, yes, it is true that noise affects
the storage requirements. But, a good compression means not only good
encoder in the HD camera, but also noise reduction before compressing,
thus achieving reasonably low streams with very high picture quality.”
According
to Damjanovski, an example from Dallmeier again, is the DF4910 that he
says can produce an excellent true 1080p HD signal with as low as 4 Mb/s
using H.264 (at 25 fps).
“With
this camera model, we can switch to a 5MP signal using the same 4 Mb/s
H.264 encoding (with slightly reduced frame rate of 10 fps). As I said
earlier, if for a particular job the very low light performance is the
most important thing, then, perhaps good quality analogue should still
be considered.”
How important is lens selection with HD cameras? Is digital or optical zoom preferable, or both?
“The
lens is most important thing after sensor quality,” says Damjanovski.
“Whether I prefer digital or optical zoom, it all depends in what
context. With the Dallmeier’s Panomera design for example, digital
zooming looks quite different. So, even though I would usually argue
that optical zoom offers better magnification of details.
“In
the case of Panomera it is different because the Panomera digital
zooming far outperforms optical zooming simply because of the different
approach in designing this multi-sensor multi-focal camera. With
Panomera’s digital zooming you can see the whole picture without losing
the details where you have not zoomed in, and this is done for both live
and playback video.
“With a normal optical zoom once you point the camera to a specific area that is it - you can’t see anything else,” Damjanovski says.
“And
of course, if you have recorded such a zoomed in video signal and
recorded it, it is not possible to retrieve what the zoomed camera has
not seen. Certainly if you know where and when the incident will occur,
and zoom in that direction, the optical zooming will be more
beneficial.”
“In
the past, HD cameras would not be recommended for low light
applications. However, with the continuous improvements in technology,
HD cameras are now available for these conditions”
What about the new H.265 standard? Is it likely to reduce the bandwidth
demands of MP video streams and/or lead to higher resolution cameras
being adopted – bigger 5MP cameras? Or do you argue for many
installations, particularly indoors, 1080p is going to be more than
enough?
“The
upcoming H.265 will further improve network capacity and design, but I
don’t think it will not encourage (nor stop) any development on resolution,”
Damjanovski says. “It is only going to be as useful as the H.265
encoder chips get introduced into our CCTV products. This might be very
soon, or it may take another 5 years perhaps.
“Yes,
it is said that it will offer at least 50 per cent bandwidth saving
over H.264 for the same visual quality, and this would certainly be
welcomed in CCTV. But this bandwidth saving will be paid for by the
higher processing power that will be required from the PC machines
decoding such compression in the software. So, once again, with H.265,
we will come to yet another demand for new and faster computers, better
network switchers and better network designs.
“The
fact is, the “good old” MPEG-2 is still available and in many cases
like your cable television) still used, without stopping the HD
technology develop. In my opinion the biggest benefit our industry could
have is the development of new sensor technologies with better low
light performances (one of which is back-illuminated sensors) higher
dynamic range and smaller sensor size, with the very important - lens
quality improvements.”
Meanwhile,
Pacific Communications Mark Shannon says that from the end-user’s
perspective, the key features of a quality HD camera, as a minimum, are
brilliant images, the ability to show near real life images (picture and
colour rendition accuracy), sharp focus, low light capabilities
including Day/Night operation, good wide dynamic range, and low
bandwidth requirement.
Shannon
says that installers should also look for cameras that provide ease of
set up, configuration, and installation. These features are provided by
cameras with attributes including a local monitor output for lens setup,
Auto Back Focus, convenient location of Ethernet connection at the back
of the camera and a variety of mounting options and accessories.
And when it comes to 720p or 1080p Shannon says it’s all about the application and the budget of the customer.
“Camera
selection is still as balanced a consideration today as it has ever
been with analogue,” he explains. “However, at present the network
bandwidth and storage are additional considerations. System design and
camera application is a skill and not a one size fits all and this will
never change.”
Shannon
says that in recent years, HD cameras have come a long way in
overcoming their inadequacies such as performance degradation in low
light and strong backlight.
“In
saying this, all cameras need lighting to provide good images and
accurate rendition, whether it be overt (white light) or covert (IR
light) depends on the applications,” he explains. “In the past,
HD cameras would not be recommended for low light applications. However,
with the continuous improvements in technology, HD cameras are now
available for these conditions.
“Lens
selection is also critical with HD cameras. In most applications,
optical zoom is generally used because it gives an accurate
magnification of the image (does not introduce artefacts).”
According
to Shannon, H.265 should be seen in the light of the ongoing
improvements taking place in the video surveillance market.
“Ten
years ago, no one imagined that HD will be in the IP video surveillance
market,” he explains. “Today, HD cameras are the norm in the IP video
surveillance market. In the future, the advancement of technology will
go hand in hand with the improvement of IP surveillance cameras;
therefore, there will be a migration to higher resolution with better
compression and storage on offer.”
Over
at Axis Communications’ Chris Tangsilsat says key features of a quality
HD camera for end users include things such as pixel count, frame rate
and colour representation but he points out they are only the tip of the
iceberg when it comes to what end users look for in a quality HDTV IP
camera.
“We
also need to consider versatility as the objective of having
surveillance for most end users is to obtain ‘usable’ video at all times
regardless of lighting and other environmental conditions,” he
explains.
“For
example a HDTV camera located in a building lobby may provide usable
quality images for the majority of the day but is subjected to intense
backlight in the late afternoon and inadequate lighting after hours.”
When
it comes to installers, Tangsilsat says that apart from quality images
he thinks the majority of systems integrators out there would place an
equally high value on the reliability and ease of installation of these
units.
“Whether
the installer spends 20 minutes or 1 hour installing and configuring a
camera will make a sizable impact on labour cost, especially when you
consider that some installations could potentially consist of hundreds
or thousands of cameras either at a single site or spread across
multiple locations,” Tangsilsat says.
“Post
installation, the reliability of the product will determine how much
time the installer keeps investing resources in returning to the same
site for maintenance and repair, or is able to move on and tackle the
next project.”
Interestingly,
Tangsilsat says he doesn’t believe there is what could be considered to
be a better resolution format – either 720p or 1080p when it comes to
HD.
“It’s
more important to identify the customer’s requirement in terms of level
of detail vs. coverage area,” he says. “For example identifying
customers entering a store may require a 720p HDTV camera focused on an
area that’s 2 meters wide, while keeping track of whether a meeting room
is occupied may only require an SVGA (800x600) camera covering an area 5
meters wide.
“Alternatively,
capturing license plates of trucks moving into a loading dock could
warrant the use of a 1080p HDTV camera. There will always be a need for a
large variation in resolutions. Additionally, implementing an effective
surveillance solution could be as simple as using a pair of 720p HDTV
cameras in a small retail environment.
“In
such a case, a camera is placed at the entry point using a high focal
length lens to capture of the faces of anyone entering in detail, while
another camera of the same type would use a wide angle lens to provide a
general overview of the store. It’s all about strategic placement and
identifying where the customer requires that extra level of detail.”
And what are the weaknesses of HD cameras in low light and in backlight?
“If
you were to ask me this same question 5 years ago I would say that in
extreme low light conditions there are some quality analogue cameras
which will outperform the IP offerings,” Tangsilasat says.
“However,
due to the continued development of IP surveillance technology, I can
say that the latest generation of HDTV IP cameras offers superior image
sensors and encoding chipsets and will have better low light performance
compared to their current model analogue counterparts.
“Low
light performance through features such as Axis’ Light Finder, however,
have not been the only development as in order to increase the level of
versatility, features such as Wide Dynamic Capture are also available
in order to cope with strong backlight scenarios. All of this leads to a
usable quality image containing less artefacts/white noise resulting in
lower storage requirements.”
When it comes to optical or digital lens selection, Tangsilsat says he thinks lens selection is highly critical.
“A
good quality lens will truly demonstrate what the camera is capable or,
while a poor quality or incompatible lens will degrade and misrepresent
the quality of the camera,” he explains.
“Installers
will notice that each Axis IP camera will always include a lens as part
of the same product code. This is because all lenses which are included
with the cameras along with optional types listed on our website have
undergone testing within our R&D to confirm they are compatible with
the intended model and provide the optimum image quality.”
According
to Tangsilsat, optical vs. digital, this has been a topic of discussion
ever since megapixel cameras were first introduced and he says it will
continue to be so as higher megapixel cameras evolve alongside higher
optical zoom types.
“There
really isn’t a right or wrong here - in most cases the choice comes
down to the end user’s requirements and resources in place,” he
explains.
“Digital
zoom will allow the user to retain a wide general overview of a scene
with limited ability to zoom into certain areas, while optical zoom
sacrifices the general overview in place of superior detail on areas of
interest.
“Again,
this comes down to the end user requirement as one customer may just
want a static high resolution, wide angle camera to record with the
ability to digitally zoom after an incident. Another customer may have a
control room with operators actively manning the PTZ cameras with
optical zoom.”
Tangsilsat
says the new H.265 standard is definitely interesting news and he
believes that once adopted it will ensure a reduction in both bandwidth
and storage requirements.
“However,
whether we will see a push within the market for higher resolution
cameras as a direct result remains to be seen as there are other factors
to consider when it comes to usable quality images in surveillance.
“These
factors include low light performance. Due to the way current image
sensors convert light into images, a 720p HDTV camera will outperform a 5
Megapixel or higher resolution model in low light scenarios regardless
of post capture compression method.
“Also
important is frame rate. IP cameras up to 1080p HDTV resolution will
easily achieve a full 25/30 frames per second. At 3 Megapixel this
typically drops to around 21 fps, and at 5 Megapixel 12 fps. Will moving
into higher resolution ranges regardless of compression method start to
result in unusable frame rates? That’s something to think about.”
“1080p
cameras will easily achieve a full 25/30 frames per second. At 3
Megapixel this drops to around 21 fps, and at 5 Megapixel, 12 fps. Will
moving into higher resolution ranges start to result in unusable frame
rates?”
Source: http://www.securityelectronicsandnetworks.com/NewsDetail/13-03-22/choosing_hd_cameras_part_one.aspx
