Lawmakers, policy makers, broadcasters
and consumer electronics vendors today gathered in Washington, D.C.,
for an event marking the commercial launch of Mobile DTV.
The event, held in the Rayburn House
Office Building, is giving those in government a firsthand look at
mobile phones, media table adapters, media players and portable sets
capable of receiving Mobile DTV while on the go.
Hosted by the Open Mobile Video Coalition
(OMVC), the National Association of Broadcasters (NAB), and the
Advanced Television Systems Committee (ATSC) and sponsored by Dyle
mobile TV, LG Electronics, Harris, Samsung, the Mobile500 Alliance,
Elgato and Rentrak, the event demonstrates Mobile DTV is a viable
broadcast service.
“Today, Mobile TV is live in 50 markets reaching more
than half of the U.S. population,” said Vince Sadusky, president of the
OMVC and president and CEO of LIN Media. “Now that the first consumer
devices are available in retail stores, we are excited to celebrate the
commercial launch of Mobile DTV.” Currently, more than 130 stations are
on air in those 50 markets with Mobile DTV.
The event included demonstrations of the
new Samsung Galaxy S Lightray 4G* smartphone, the first commercial
mobile phone equipped with Dyle mobile TV service. Wireless carrier
MetroPCS is making the Galaxy S Lightray 4G with Mobile DTV reception
available to consumers.
Other demonstrations included new accessory devices
to provide mobile TV capability to tablets and media players and a new
portable mobile TV equipped with WiFi capability.
The Capitol Hill event also marks the
commercialization of the new Mobile Emergency Alert System (M-EAS) that
goes beyond today’s electronic text alerts for mobile devices, offering
real-time video, maps, photos, and urgent information in the event of an
emergency. Demonstrated by LG Electronics and Harris Broadcast, M-EAS
is currently being standardized by the ATSC, which also developed the
A/153 Mobile Digital TV broadcast standard.
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Friday 21 September 2012
Friday 11 May 2012
Current Trends Shaping the Television Industry
TV Embraces the Internet
Thanks to Hulu and Netflix, people don’t necessarily need television
sets in order to consume media. But while the recession prompted
consumers to cut back on dining out and other frivolities, they did
continue to spend on home entertainment, which has prompted many TV
manufacturers invest in new, Internet-enabled models. So even while
traditional television is being challenged by the rise of Internet video
streaming, manufacturers are embracing new consumer behaviors.
Look at Sony’s search-centric Google TV,
for example. The set allows user to search for “Seinfeld,” and call up
air times, cast information from IMDB and information on
where the content can be viewed on the web — it’s a more holistic and
streamlined experience.
There are several other ways to stream
web content to your TV, including the use of connected devices like
Boxee Box. The
symbiosis between Internet, apps and TV could keep the TV industry going
strong.
The Box Office Pulls People Away From Their TVs
The movie industry has also affected TV consumerism — the rise of 3D
movies has pulled consumers away from their sofas and into cinemas,
where they can indulge in a highly visual experience for a few bucks
more than a regular movie. While 3D TVs exist, they come at a hefty
price and don’t yet provide the same level of viewer immersion.
3D technology was touted as the next frontier in the TV industry, but
consumers don’t seem to be latching on — in a 2010 study, 83% of survey
respondents said 3D technology isn’t enough to make them want to buy a
new TV, and nearly one-third of people say 3D doesn’t enhance the
viewing experience. It seems that 3D technology is preferred on the big
screens of movie theaters and not in one’s home. Just 3% of TV owners
own a 3D TV, but there’s not much 3D content out there to keep them
entertained. The resistance also can be attributed to the glasses
factor: many people find them uncomfortable, inconvenient and, in some
cases, nausea-inducing.
LCD and Flat-Panel Screens Dominate
More than 60% of Mintel’s respondents own a flat-panel TV.
Competition among television brands in 2010 drove down the price of TV
sets, which in turn spurred growth in the volume of TV sales.
While Sony remains the big fish in the TV space — commanding 20% of
the market share — bargain brands are gaining steam. Samsung and LG both
made big strides in market share, but Vizio is presenting the greatest
challenge to Sony, thanks to its placement in stores like Walmart and
Sam’s Club.
Value brands like Vizio, which boast similar technology to the
premium brands, but at a better price, have slashed prices by 20%. A 55″
edge-lit LED LCD HDTV was sold for $1,829.99 by Vizio and for $2,299.99
by Sony and Samsung — that’s a $400 spread, and 30% of consumers say
they’d go with an unfamiliar brand if it would save them more than $200.
But it’s not enough to have a flat-panel TV — LCD screens represented
78% of factory sales in 2010. Although sales totals declined — much in
part because the actual price tag on LCD TVs has decreased — LCD
penetration more than tripled to 39% from 2006 to 2010.
And apparently, size matters. If you’re going for all the high tech
features, you may as well go big or go home. Half of the TVs in America
are now in excess of 40″.
Despite the sales spikes for these new TV features, the average
number of TVs per household has not changed — the market share is rising
because consumers are “trading up” for bigger and better televisions.
TV Is Going Social
Television
viewers are often multitasking — they watch their favorite shows
while interacting on social media platforms via their tablets,
smartphones and laptops. A Deloitte survey found that 42% of Americans
surf the web while watching television, 29% talk on their phones while
the TV is on and 26% of consumers are texting or sending IMs.
According to TV Guide, Twitter leads Facebook when it comes
to social engagement during a show’s airtime — a phenomenon known as “social TV.”
50% of users said they tweet about the show they’re currently watching,
while only 35% say they post to Facebook. Interestingly, the most
social TV shows are not necessarily the ones with the highest Nielsen
rankings — they’re the ones that spur conversation and have super
passionate fans. American Idol, Glee and Smallville
cracked the top ten, even though they’re all in different echelons of
Nielsen ratings.
At Mashable
Connect, TV Guide‘s Christy
Tanner spoke about social TV and where it’s going — the video of her
talk is embedded above. Tanner said the reason people are inclined to
share their opinions on their favorite TV shows is that it’s not a
controversial topic, like politics, and it’s not boring, like the
weather. And so, we share our thoughts with our friends on Facebook,
Twitter and other sites.
Advertising Is More Targeted
Some TV brands have begun to target demographics more specifically. While they used to target the “Under 45” crowd, Samsung now targets young families, males under 35 and active and childless 25-34-years olds.
Likewise, Toshiba ads speak to independent millennial women; Sharp
appeals to tech-savvy consumers with Star Trek actor George
Takei, and Vizio targets shopping-savvy and trendy twenty-somethings.
You might also notice more advertising targeted toward fathers. Dads
are more receptive to television product marketing, as tech is something
male friends talk about over beer, and a father could justify a new
television as a big investment that will benefit and entertain the whole
family. Television companies may try to target dads directly — maybe
with a commercial of one family with a souped up TV being happier than a
family without such a TV — or via the children. A 3D TV would make
gaming and other TV-based activities more exciting, for example, so the
kids might give dad that extra push to splurge.
Demographic Trends and Fun Facts
The Mintel report is littered with interesting tidbits and data
gleaned from its survey. Here are some interesting trends and stats:
- Flat-panel TVs remains most dominant in households with incomes that exceed $100,000. Not surprisingly, this demographic is also more likely to own a TV larger than 50”.
- Purchasers tend to want the biggest TV screen they can afford, which suggests that size trumps technology and features.
- Those under 45 or with children are more likely to have a large TV screen.
- Interest in Netflix is as high among 45-54 year olds as it is among 25-34 year olds.
- 21% of respondents would pay up to $100 more for an energy-efficient TV.
- 34% of respondents would like to upgrade at least one TV in the home.
- 49% of respondents like to have a TV in the bedroom.
- 18% of respondents like to have a TV in the kitchen.
Tuesday 8 May 2012
PURE VIDEO HD
PureVideo HD technology is the combination of a dedicated video processing core on the NVIDIA GPU and software in the NVIDIA drivers that delivers superb video quality with minimal CPU use and low power consumption when playing Blu-ray or HD DVD discs on a PC.It is the essential ingredient for the ultimate high definition movie and video experience on a PC.
Revolutionary New Video Processing Architecture
NVIDIA GeForce 8 Series and above incorporate a revolutionary new video processing architecture, making them them capable of offloading Blu-ray video decoding (H.264, VC-1, MPEG-2) from the CPU. This added processing power gives PureVideo HD technology the ability to support more features as they are added to Blu-ray movies, including “picture-in-picture”, interactive games and menus, and higher bit-rate / higher video quality.
NVIDIA GeForce 8 Series and above incorporate a revolutionary new video processing architecture, making them them capable of offloading Blu-ray video decoding (H.264, VC-1, MPEG-2) from the CPU. This added processing power gives PureVideo HD technology the ability to support more features as they are added to Blu-ray movies, including “picture-in-picture”, interactive games and menus, and higher bit-rate / higher video quality.
Low CPU Utilization and Power Consumption
PureVideo HD technology on the GPU takes on the processing-intensive video decoding task, freeing the CPU and 3D engine to run other applications while playing a high-definition movie. Lower CPU utilization can result in reduced power consumption, heat and noise, and longer battery life.
PureVideo HD technology on the GPU takes on the processing-intensive video decoding task, freeing the CPU and 3D engine to run other applications while playing a high-definition movie. Lower CPU utilization can result in reduced power consumption, heat and noise, and longer battery life.
Superb Picture Quality
NVIDIA PureVideo HD technology delivers outstanding picture clarity, ultra-smooth video, vivid color, and precise image scaling for video and HD DVD and Blu-ray movies. PureVideo HD accelerates and enhances high-definition movies delivering life-like images that have up to six times the detail of standard DVD movies at resolutions up to 1080p - the highest HD resolution available.
NVIDIA PureVideo HD technology delivers outstanding picture clarity, ultra-smooth video, vivid color, and precise image scaling for video and HD DVD and Blu-ray movies. PureVideo HD accelerates and enhances high-definition movies delivering life-like images that have up to six times the detail of standard DVD movies at resolutions up to 1080p - the highest HD resolution available.
PureVideo HD technology is a core ingredient for playing visually stunning movies on a PC. Leading PC manufacturers, including DELL, HP, Toshiba and Acer, have adopted NVIDIA GeForce GPUs with PureVideo HD technology to power their PCs with Blu-ray and HD DVD drives.
Friday 27 April 2012
3D camera for broadcasting
HXR_NX3D1U
The HXR-NX3D1U is a compact, lightweight, WorldCam 3D/ 2D NXCAM
camcorder suitable for principal photography in small budget productions
or as a B camera in big budget productions. Thanks to its small size,
low weight, simple operation and exceptional flexibility it can shoot 3D
at camera angles that were never possible before.
- 3.5-inch Xtra Fine LCD™ display (1229K) providing user-selectable 2D or glassless 3D viewing.
- User-selectable HDMI® output format with output of horizontally compressed left and right images packed into a single frame.
- Multi-Format Recording: 3D 60i/50i/24p & 2D 60p/60i/50p/50i/25p/24p
- Large capacity, 96GB of internal memory enabling extended recording in 3D mode for approximately 7.5 hours.
- Dual Exmor R® Sensor – ¼ type with ClearVid pixel array provides 4.2 Million pixels, high image fidelity
- Optical SteadyShot™ w/Active Mode and 10x Optical Zoom (34.4-344mm) in 3D
- Balanced, two XLR audio inputs: Uncompressed 16-bit LPCM or Dolby Digital
- The supplied Content Management Utility 2.1 software enables conversion of MVC video files to 2D AVC files with independent left and right channels.
PMWTD300
- Dual 1/2-inch type Exmor Full-HD 3CMOS sensors
- Dual lens system
- XDCAM EX recording
- SxS card slots (L/R x 2)
- 3D/2D recording modes
- Intuitive convergence control with a dedicated dial feature
- Viewfinder with 3.5-inch type color LCD
- HD-SDI out (L/R dual stream, audio and TC embedded)
- HDMI out (3D/2D) for viewing on consumer 3D displays
- Genlock in & TC in/out for integration with multi-camera systems
Monday 23 April 2012
THE 3D
All of the 2010 3D TV models – both LCD and
Plasma –
required Active Shutter Glasses, which have high-speed LCD shutters for
each
eye that are electronically synchronized to the sequential right and
left
images generated by the TV every 1/120th of a second. 2011 has resulted
in a
lot more available 3D content and two important developments in 3D
technology:
a new generation of 3D TVs with Active Shutter Glasses, and a new 3D TV
technology called Film Pattern Retarder (FPR) that uses very light
weight and
inexpensive Passive Glasses that are similar to ordinary polarized
sunglasses,
and identical to the 3D glasses used in most 3D movie theaters. The FPR
3D TV
technology doesn’t need high-speed electronic shutters because it uses
circularly polarized light filters to keep the right and left images
separate
for each eye.
3D TV technology is still relatively new so it’s
not
surprising that most consumers (and many reviewers) are still trying to
sort
out all of the manufacturer’s claims, figure out what they mean, and
what they
should do next. There are some conflicting and unsubstantiated
statements about
3D TV technologies that are being made in a badgering manner just like
in the
classic tale of The Emperor’s New Clothes. The object of this
article is
to provide detailed objective test results that will let you decide what
is
really there, or not there… But the most important issue of all is
whether
either of these technologies is able to provide an enjoyable and
convincing 3D
viewing experience – we’ll answer that below, but first we’ll back it up
with
lots of objective evidence.
There are a number of very interesting (and
frequently
misunderstood) 3D imaging and visualization issues that need to be
examined for
both of these 3D TV technologies in order to straighten out the
incorrect and
confusing information about them. This article will provide an objective
in-depth analysis of both 3D technologies. We have plenty of measurement
data,
which provides lots of good objective evidence, but the most interesting
and
important part in evaluating 3D is the actual 3D imaging and
visualization
itself, and that only happens inside the brain, so instruments cannot
help with
that part of the evaluation. We used lots of high quality 3D content
including
3D movies, photos, images and test patterns. We will describe a series
of quantifiable
3D visual tests that anyone can duplicate at home to verify our
results
and conclusions on 3D TV imaging for themselves.
Saturday 21 April 2012
HOT SPOT TECHNOLOGY FOR CRICKET BROADCAST
100% accuracy in catching the thinnest of edges
HOT SPOT
HotSpot is a television innovation - first seen during Channel Nine's
coverage of the 2006-07 Ashes - that uses infrared camera technology to
determine whether a batsman has made contact with a delivery, and if so,
which part of his bat or body made contact.
WORKING PRINCIPLE
Two powerful thermal-imaging cameras are positioned above the field of
play, behind the bowler's arm at either end of a ground. These can
remotely sense and measure the minute amount of heat generated by the
impact of a cricket ball against another object. Computer technology
then generates a negative image on which the point of contact is
highlighted as a red friction "hot spot" for a second or two. HotSpot
doesn't only record impacts between the ball and other objects, but also
the bat hitting a pad or the ground.
If there are two simultaneous hot spots - ball on pad
and bat brushing pad - close together, how do you differentiate?
Two hot spots would appear, one fractionally before the other, according
to the sequence of the events. HotSpot is therefore useful in instances
of bat-pad impacts in determining whether the ball hit bat or pad
first.
What technology does the application use?
HotSpot uses technology developed in the military for tank- and
jet-fighter tracking. The technology was adapted for television by BBG
Sports, the Australian company responsible for the Snickometer, in
conjunction with Sky Sports. Channel Nine producer Steve Crawley
described HotSpot as "100% backed up by science", as opposed to other
applications.
Has it been used in any other sport?
HotSpot has only been used in cricket - though its services are not
available to umpires under the current referral system - but work is
underway to adapt the technology for use in tennis.
Thursday 19 April 2012
HAWK EYE TECHNOLOGY IN SPORTS BROADCASTING
Hawk-Eye is a complex computer system used in cricket, tennis and other sports to visually track the trajectory of the ball and display a record of its most statistically likely path as a moving image. It was developed by engineers at Roke Manor Research Limited of Romsey, Hampshire in the UK, in 2001.
Method of operation
All Hawk-Eye systems are based on the principles of triangulation
using the visual images and timing data provided by at least four
high-speed video cameras located at different locations
and angles around the area of play.[2]
The system rapidly processes the video feeds by a high-speed video
camera and ball tracker. A data store contains a predefined model
of the playing area and includes data on the rules of the game.
In each frame sent from each camera, the system identifies the group
of pixels which corresponds to the image of the ball. It then calculates
for each frame the 3D position of the ball by comparing its position on
at least two of the physically separate cameras at the same instant in
time. A succession of frames builds up a record of the path along which
the ball has travelled. It also "predicts" the future flight path of the
ball and where it will interact with any of the playing area features
already programmed into the database
Hawk-Eye DeSpin Graphics demonstrate how far a delivery has deviated
after pitching. Whilst the blue trajectory below represents a ball that
does not spin or seam, the red ‘actual delivery’ shows just how much
turn the spinner has achieved.
The pure tracking system is combined with a backend database
and archiving capabilities so that it is possible to extract and
analyse trends and statistics about individual players, games,
ball-to-ball
comparisons, etc.
Cricket
It is in cricket TV broadcasts that Hawk-Eye first made its name. The
technology is used by broadcasters to resolve LBW shouts and, as with
its tennis counterpart, to generate easily-digestible statistics to
enhance the viewing experience. Viewers now expect Hawk-Eye to show
whether a batsman should have been given ‘in’ or ‘out’: the technology
predicts the path of the ball as it comes out of the bounce, thus
determining whether the ball would have hit the stumps.
Whilst it is not used officially by the ICC, Hawk-Eye’s six years of
technical experience have made it a firm favorite with fans and players
of the gam
LBWs
Viewers now expect Hawk-Eye’s verdict on lbw ‘shouts’; a testimony to Hawk-Eye’s reputation for accuracy and reliability. The company’s experienced operators will deliver the relevant trajectory, half-mixed with the equivalent video sequence, in time for the first replay. This gives commentators and viewers adequate time to discuss and digest the result before the next ball has been bowled.
Hawk-Eye helps to resolve the following three issues:
- Would the ball have hit the stumps?
- Did the ball pitch in-line?
- Did the ball hit the batsman in-line?
Beehives
Beehives show where the ball has passed the
batsman.As with the Pitch Map, the coloured balls correspond to the
number of runs that the batsman has achieved from that delivery.
Hawk-Eye Beehives can now be shown against a photo realistic or virtual
realistic world, as with the Wagon Wheel feature.
RailCam
The ‘RailCam’ (side view) shot of the VR World can be used to represent
differences in speed, bounce and delivery. The trajectories are
animated, whilst the speeds provide further evidence of a bowler’s
variation or a telling comparison between athletes.
Ball Speeds
Hawk-Eye now has the ability to supply ball speeds as
reliably as a radar gun, as demonstrated during the ICC World Twenty20
in South Africa
Monday 9 April 2012
how to build a low cost prompter
A normal teleprompter comes with a 15 inch screen. But
since I was doing single person stand-ups I realized that the 7 inch
monitor I have laying around would make a great monitor for my needs. In
case you are interested you can purchase a 7 inch LCD monitor for a
bit over $100 these days. Keep in mind that you don't need high rez of
super color rendition as a prompter plays in black and white, so any
inexpensive monitor from a 7 inch like I used to a 15 inch computer
monitor that costs $150 will work fine.
There are two types of design in prompters. The
traditional set-up's basically a box with a monitor that lies with the
screen facing up. A 45 degree piece of glass (slightly coated with a
mirror-like surface) reflects the monitors image to anyone standing in
front of the lens. See illustration below.
The second kind of prompter set-up involves the same principles as above but the box that encloses the set-up is eliminated and all you are left with is a monitor with a mirror hinged on one side sort of like how a book opens. It's lighter and easier to handle. But it also allows more light to wash out your screen. Since my standup's will be outside, I prefer the older style box enclosure as it creates a dark area around the monitor. |
You can use anything from sheet metal to more
rigid steel for the enclosure just as long as it will make a ridged box
capable of holding the glass. In my case I used 16 gauge steel, a thin
but sturdy steel that you can purchase in small sheets at hardware
stores such as the Home Depot. They also sell a very thin 24 gauge, but I
wanted rock sturdy at the cost of some weight. So pick what works for
you. Remember in the end, it has to hold a piece of glass so don't go
too thin, like sheet metal.
|
Once constructed, this prompter is about 9 inches square. That can be a
pain to transport, so I designed my box to collapse. I've seen folks
make hinged-type boxes but I decided on a simple but effective way,
using wing screws which I could screw the box together with.
After cutting the metal pieces to the appropriate size necessary to
create a box that will fit around the monitor (I used a Dremel tool with
a cut off wheel to cut the metal), I needed a way to attach the two
sides of the box to the top piece. I cut pieces of aluminum L shaped
metal and riveted these brackets to what would become the top panel of
the box.
- Above: The top panel with L bracket showing. Notice three rivets used to attach it to panel. Also notice this is the painted version. I used a textured paint and baked it on by painting the final assembly, then placing it in an oven at 400 degrees for about 10 minutes. Doing so adheres the paint so it is more difficult to chip or scratch.Also notice the holes on either end of the L bracket (silver side). I drilled those holes so the wing screws would fit thorough them. Next next thing to do is to give the wing nuts something to screw into. I found nuts that fit the screws and attached them to the inside of the L bracket. Below is the method I used. The following visual presentation is not the actual L bracket but done after the fact so I could show you how it is done.
1)Above: I drilled holes the same size as the screw size
2)Above: I placed the nut over the hole - 3)Above and below: Using a metal epoxy and a Q-tip (cotton removed) I epoxied the nut to the steel
- The nut glued and ready to go in about 15 minutes. I ended up gluing four of these to each side of the two L brackets. This will accept the wing screw and make a three sided box once attached.
- Above: The finished piece. You are looking at the inside of the top piece of the box frame with screw glued and all painted. Notice how this glue expands to three times its size engulfing he screw like it's been welded.
Next, I lined the side panels up to the top panel, marked the hole location and drilled out the two holes in each side panel. I glued cup washers to the outside of each hole on each side panel so that when I tighten the wing screw it has something to rest on other than simply the painted side of the panelI now have a three sided box, top, and two sides. There are a number of ways I could have attached the three sided box to the monitor such as creating a bracket the monitor rested in or by using using velcro. Since I will use this configuration in the future, I decided to do the same thing to the monitor that I did to the top panel, drill holes and glue nuts inside so I could easily screw the side panels to it. This would allow me to use the monitor on it's own when I needed and as a prompter monitor. And by screwing the monitor to the upper panels I created a rigid box.
- Next I needed to figure out how to make a tray for the glass. A word about the glass. The glass I used is a piece of glass that has a minor reflective coating on it one side (like one way mirror but not such a mirror and not so dark). You can get such glass at a local glass shop. They call it beam-splitting glass. I simply asked to see what varieties they had and found one that cut down light the least, while offering a slightly reflective surface so the monitor could be seen by the reader. You will end up with glass that cuts light down anywhere from 1/2 stop to 2 stops. If you really are handy, you can make your own beam-splitting glass. Read this.The glass needs to be at a 45 degree angle when installed to work properly. I used more of the L bracket and attached a piece to either side of the inside of the sides of the prompter box with rivets making a tray the glass could lay in. I also attached a small piece to the bottom of the bracket to act as a stop so the glass would not slide down. I put a small clear rubber stopper on the back of the tray and added the softer side of velcro strips to the bottom of the tack so the glass had something to rest on. See below.The attached L bracket with the additional stopper at the bottom and velcro on the track where the glass will rest.A blurry shot looking through the glass. Notice the reflection of the computer monitor and keyboard in what is the mirrored side of the glass. facing the camera here.And for the final touch I needed something to prevent light from spilling into the box from the camera side. If you don't stop the light from being seen by the talent it washes out the reflected lettering on the glass. Prompter people use a simple method of attaching the sticky side of Velcro all the way around the inside of the box on the lens side, then using a piece of black material simply stick it to all sides. That's what I did also.The material I cut to fit the backside of the prompter hole. Notice I cut a hole at the center of the material so I could fit the lens through it. A picture if the material in action appears later.I did not go crazy with a method of mounting this. There are two ways to mount a prompter. One is called free standing. Freestanding prompter means the prompter sits on it's own stand in front of the lens. This method doesn't allow much camera panning. The second method is to mount the camera to the camera plat and tripod. This method give the most mobility and allows you easy pan and tilt.In my scenario I only needed it to sit in front of the camera so I went with the free sanding method. As the pictures below showed, I took a six inch Matthews plate and placed the stud into a grip knuckle attached to a stand. The flat side of the plate now acts as a small table. Since my monitor has a Anton Bauer fitting and battery I simply added a piece of velcro to the top of the plate and the battery and used four small bungies for extra support. It worked perfectly. There are many more ways of making a freestanding adaptor and if need be a metal or wooden riser so it can be attached to the front of the camera and tripod.
Sunday 8 April 2012
BACK FOCUS IN THE BROADCAST INDUSTRY
BACK FOCUS
If you find that your focus is sharp when you are zoomed in but soft
when zoomed out, your back focus needs adjusting. This
normally only happens to cameras with detachable lenses — consumer-level
camera users
shouldn't have to worry about it.
Technical Note: Back focus refers to the "focal flange length". This is the distance between the rear lens element and the CCD.
- A camera with a back focus ring. It will be located toward the rear of the lens housing.
- A back focus chart like the one pictured is helpful, but any object with sharp contrast will do
How to Adjust the Camera Back Focus
- Set your camera on a tripod or stable mount, with your subject (back
focus chart or other contrasting object) at least 20 metres/70 feet
away (or as far as possible).
- Your iris should be wide open, so it's better to perform this
operation in low light. Alternatively, add some shutter speed or a ND
filter.
-
If your lens has a 2X extender, switch it to
1X.
-
Zoom in on your subject.
-
Adjust the focus normally until the picture
is sharp. If you're using a back focus chart, the centre of the
chart will appear blurry - your focus is sharpest when the blurred
circle is smallest. (You can simulate this effect by looking at the
chart above and defocusing your eyes.)
-
Zoom out.
-
Loosen the back-focus ring's locking screw,
and adjust the ring until the picture is sharp.
-
Repeat steps 3-6 until the focus is
consistently sharp.
- Tighten the back-focus locking screw.
Saturday 7 April 2012
THE WHITE BALANCE
blue tone |
orginal |
White balance (WB) is the process of removing unrealistic color casts,
so that objects which appear white in person are rendered white in your
photo. Proper camera white balance has to take into account the "color
temperature" of a light source, which refers to the relative warmth or
coolness of white light. Our eyes are very good at judging what is white
under different light sources, but digital cameras often have great
difficulty with auto white balance (AWB) — and can create unsightly
blue, orange, or even green color casts. Understanding digital white
balance can help you avoid these color casts, thereby improving your
photos under a wider range of lighting conditions.
BACKGROUND: COLOR TEMPERATURE
Color temperature describes the spectrum of light which is radiated
from a "black body" with that surface temperature. A black body is an
object which absorbs all incident light — neither reflecting it nor
allowing it to pass through. A rough analogue of black body radiation in
our day to day experience might be in heating a metal or stone: these
are said to become "red hot" when they attain one temperature, and then
"white hot" for even higher temperatures. Similarly, black bodies at
different temperatures also have varying color temperatures of "white
light." Despite its name, light which may appear white does not
necessarily contain an even distribution of colors across the visible
spectrum:
Note how 5000 K produces roughly neutral light, whereas 3000 K and
9000 K produce light spectrums which shift to contain more orange and
blue wavelengths, respectively. As the color temperature rises, the
color distribution becomes cooler. This may not seem intuitive, but
results from the fact that shorter wavelengths contain light of higher
energy.
Why is color temperature a useful description of light for
photographers, if they never deal with true blackbodies? Fortunately,
light sources such as daylight and tungsten bulbs closely mimic the
distribution of light created by blackbodies, although others such as
fluorescent and most commercial lighting depart from blackbodies
significantly. Since photographers never use the term color temperature
to refer to a true blackbody light source, the term is implied to be a
"correlated color temperature" with a similarly colored blackbody. The
following table is a rule-of-thumb guide to the correlated color
temperature of some common light sources:
Color Temperature | Light Source |
1000-2000 K | Candlelight |
2500-3500 K | Tungsten Bulb (household variety) |
3000-4000 K | Sunrise/Sunset (clear sky) |
4000-5000 K | Fluorescent Lamps |
5000-5500 K | Electronic Flash |
5000-6500 K | Daylight with Clear Sky (sun overhead) |
6500-8000 K | Moderately Overcast Sky |
9000-10000 K | Shade or Heavily Overcast S |
IN PRACTICE
Since some light sources do not resemble blackbody radiators, white
balance uses a second variable in addition to color temperature: the
green-magenta shift. Adjusting the green-magenta shift is often
unnecessary under ordinary daylight, however fluorescent and other
artificial lighting may require significant green-magenta adjustments to
the WB.
The first three white balances allow for a range of color temperatures. Auto
white balance is available in all digital cameras and uses a best
guess algorithm within a limited range — usually between 3000/4000 K and
7000 K. Custom white balance allows you to take a picture of a
known gray reference under the same lighting, and then set that as the
white balance for future photos. With "Kelvin" you can set the color
temperature over a broad range.
The remaining six white balances are listed in order of increasing
color temperature, however many compact cameras do not include a shade
white balance. Some cameras also include a "Fluorescent H" setting,
which is designed to work in newer daylight-calibrated fluorescents.
CUSTOM WHITE BALANCE: CHOOSING A NEUTRAL REFERENCE
A neutral reference is often used for color-critical projects, or for
situations where one anticipates auto white balance will encounter
problems. Neutral references can either be parts of your scene (if
you're lucky), or can be a portable item which you carry with you. Below
is an example of a fortunate reference in an otherwise bluish twilight
scene.
On the other hand, pre-made portable references are almost always more
accurate since one can easily be tricked into thinking an object is
neutral when it is not. Portable references can be expensive and
specifically designed for photography, or may include less expensive
household items. An ideal gray reference is one which reflects all
colors in the spectrum equally, and can consistently do so under a broad
range of color temperatures. An example of a pre-made gray reference is
shown below
IN MIXED LIGHTING
Multiple illuminant with different color temperatures can further complicate performing a white balance. Some lighting situations may not even have a truly "correct" white balance, and will depend upon where color accuracy is most important..
Under mixed lighting, auto white balance usually calculates an average color temperature for the entire scene, and then uses this as the white balance. This approach is usually acceptable, however auto white balance tends to exaggerate the difference in color temperature for each light source, as compared with what we perceive with our eyes.
Exaggerated differences in color temperature are often most apparent with mixed indoor and natural lighting. Critical images may even require a different white balance for each lighting region. On the other hand, some may prefer to leave the color temperatures as is.
Note how the building to the left is quite warm, whereas the sky is somewhat cool. This is because the white balance was set based on the moonlight — bringing out the warm color temperature of the artificial lighting below. White balancing based on the natural light often yields a more realistic photograph. Choose "stone" as the white balance reference and see how the sky becomes unrealistically blue.
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