How Camcorders Work 6 by nafees

7/25/2019 How Camcorders Work 6 by nafees

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How Camcorders Work

In most of the world, camcorders, or video camera-recorders, have been a

familiar sight for nearly 20 years. People take them everywhere: to school plays,

sports events, family reunions and even births! hen you go to a popular tourist

spot, you are surrounded by them. amcorders have really taken hold in the "nited

#tates, $apan and many other countries around the world because they are an

e%tremely useful piece of technology that you can own for under &'00 (or more

than &)00,000*.

+ow can such a small device do so much Particularly for anyone born before the

)-0s, it/s simply amaing that 1uality video cameras are now readily available as

consumer items, and that they/re so easy to use. In this article, we/ll look inside

these e%tremely popular devices to nd out what e%actly is going on. e/ll e%plore

traditional analog camcorders and also look at the technology used in digital

camcorders.


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Camcorder with the outer shell removed

The Basics

3 typical analog camcorder contains two basic parts:

3 camera section, consisting of a 4, lens and motors to handle the oom,focus and aperture

3 56 section, in which a typical 75 56 is shrunk down to t in a much

smaller space.

7he camera component/s function is to receive visual information and interpret it as

an electronic video signal. 7he 56 component is e%actly like the 56 connected to

your television: It receives an electronic video signal and records it on video tape as

magnetic patterns (see +ow 56s orkfor details*.

7hese two sections are easily seen in the following photos.

The camcorder's VCR unit
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The camcorder's camera unit

The camera lens system


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The camcorder's Charge Coupled Device CCD!

The in"rared auto"ocus mechanism
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The motors that "ocus the camera lenses

3 third component, theview#nder, receives the video image as well, so you cansee what you/re shooting. 5iewnders are actually small, black8and8white or color

televisions, but many modern camcorders also have larger full8color 94 screens.

7here are many formats for analog camcorders, and many e%tra features, but this is

the basic design of most all of them. 7he main variable is what kind of storage tape

they use.

4igital camcorders have all these same elements, but have an added component

that takes the analog information the camera gathers and translates it tobytesof

data. Instead of storing the video signal as a continuous track of magnetic patterns,

it records the picture and sound as )s and 0s. 4igital camcorders are so popular

because you can copy )s and 0s very easily without losing any of the information

you/ve recorded. 3nalog information, on the other hand, fades with each copy 88

the copying process doesn/t reproduce the original signal e%actly. 5ideo information

in digital form can also be loaded ontocomputers, where you can edit it, copy it, e8

mailit andmanipulate it.

In the ne%t section, we/ll look at the heart of the camcorder, the semiconductor

device that converts visual information into an electronic signal.
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CCD

The CCD

9ike a lm camera, a camcorder sees the world through lenses. In a lm camera,

the lenses serve to focus the lightfrom a scene onto lm treated with chemicals

that have a controlled reaction to light. In this way, camera lmrecords the scene in

front of it: It picks up greater amounts of light from brighter parts of the scene, and

lower amounts of light from darker parts of the scene. 7he lens in a camcorder also

serves to focus light, but instead of focusing it onto lm, it shines the light onto asmall semiconductorimage sensor. 7his sensor, a charge-coupled device(4*,

measures light with a half8inch (about ) cm* panel of '00,000 to ;00,000 tiny light8

sensitive diodescalledphotosites.


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needs to measure the levels of these three colors to be able to reproduce a full8color

picture.

How the three colors mi% to "orm many colors

In some high8end camcorders, a &eam splitterseparates a signal into three

di>erent versions of the same image 88 one showing the level of red light, one

showing the level of green light and one showing the level of blue light. erent primary colors blend to

produce a full8color image. 3 camcorder that uses this method is often referred to as

a three8chip camcorder.

How the original le"t! image is split in a &eam splitter

7his simple method produces a rich, high8resolution picture. 4s are e%pensive

and eat lots of power, however, so using three of them adds considerably to the

manufacturing costs of a camcorder. ?ost camcorders get by with only one 4 by

tting permanent color lters to individual photo sites. 3 certain percentage of

photo sites measures only levels of red light, another percentage measures only

green light and the rest of the photo sites measure only blue light. 7he colordesignations are spread out in a sort of grid (the @ayer lter below is a common

conguration*, so that the video camera computer can get a sense of the color

levels in all parts of the screen. 7his method re1uires the computer

to interpolatethe true color of light arriving at each photosite by analying the

information received by the other photo sites in the vicinity. Aor a full e%planation of

this process, check out +ow 4igital ameras ork: apturing olor.
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If you/ve read +ow 4igital ameras ork, then all this has probably been familiar to

you 88 camcorders and digital still cameras both take pictures using 4s. @ut since

camcorders produce moving images, their 4s have some additional pieces you

won/t nd in digital camera 4s. 7o create a video signal, a camcorder 4 must

take many pictures every second, which the camera then combines to give the

impression of movement.

If you/ve read +ow 7elevision orks, you know that a television paints images in

horiontal lines across a screen, starting at the top and working downward. 75s

actually paint every other line in one pass (this is called a eld* and then paint the

alternate lines in the ne%t pass. 7o create a video signal, a camcorder captures aframe of video from the 4 and records it as the two elds. 7he 4 actually has

another sensor layer behind the image sensor. Aor every eld of video, the 4

transfers all the photo site charges to this second layer, which then transmits the

electric charges at each photo site, one by one. In an analog camcorder, this signal

goes to the 56, which records the electric charges (along with color information* as

a magnetic pattern on videotape. hile the second layer is transmitting the video

signal, the rst layer has refreshed itself and is capturing another image.

3 digital camcorder works in basically the same way, e%cept that at this last stage

an analog-to-digital convertersamples the analog signal and turns the

information into bytes of data ()s and 0s*. 7he camcorder records these bytes on a

storage medium, which could be, among other things, a tape, a hard diskor a 454.

?ost of the digital camcorders on the market today actually use tapes (because

they are less e%pensive*, so they have a 56 component much like an analog

camcorder/s 56. Instead of recording analog magnetic patterns, however, the tape

head records binary code. nterlaceddigital camcorders record each frame as two

elds, Bust as analog camcorders do. $rogressivedigital camcorders record video
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as an entire still frame, which they then break up into two elds when you output

the video as an analog signal. (7o learn more about analog8to8digital picture

conversion, check out +ow 4igital ameras ork: 4igitiing Informationand +ow

3nalog and 4igital 6ecording orks.*

The (ens

3s mentioned previously, the rst step in recording a video image is to focus light

onto the 4, using a lens.

7o get a camera to record a clear picture of an obBect in front of it, you need to be

able to adBust the focus of the lens 88 that is, move the lens so it aims the light

beams coming from that obBect precisely on the 4. #o, Bust like lm cameras,

camcorders let you move your lens in and out to focus light. =f course, most people

need to move around with their camcorders, shooting many di>erent things at

di>erent distances, and constantly refocusing is e%tremely diCcult.

7his is why all camcorders come with an auto"ocusdevice, usually an infraredbeam that bounces o> obBects in the center of the frame and comes back to a

sensor on the camcorder.
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n"rared auto"ocus mechanism

7o nd the distance to the obBect, the processor calculates how long it takes the

beam to bounce and return, multiplies this time by the speed of light, and divides

the product by two (because it traveled the distance twice 88 to the obBect and back

again*. 7he camcorder has a small motorthat moves the lens, focusing it on obBects

at this distance. 7his works pretty well most of the time, but sometimes you have to

override it 88 you may want to focus on something in the side of the frame, for

e%ample, but the autofocus is picking up what/s right in front of the camcorder. 7o

learn more about autofocus mechanisms, check out +ow 3utofocus ameras ork.

amcorders are also e1uipped with a )oom lens. In any sort of camera, you can

magnify a scene by increasing the "ocal lengthof the lens (the distance between

the lens and the lm or 4*. 3n optical )oomlens is a single lens unit that letsyou change this focal length, so you can move from one magnication to a closer

magnication. 3 )oom rangetells you the ma%imum and minimum magnication.

7o make the oom function easier to use, most camcorders have an attached motor

that adBusts the oom lens in response to a simple toggle control on the grip. =ne

advantage of this is that you can operate the oom easily, without using your free

hand. 7he other advantage is that the motor adBusts the lens at a steady speed,
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making ooms more Duid. 7he disadvantage of using the grip control is that the

motor drains batterypower.

#ome camcorders also have something called a digital )oom. 7his doesn/t involve

the camera/s lenses at allE it simply ooms in on part of the total picture captured by

the 4, magnifying the pi%els. 4igital ooms stabilie magnied pictures a littlebetter than optical ooms, but you sacrice resolution 1uality because you end up

using only a portion of the available photo sites on the 4. 7he loss of resolution

makes the image fuy.

=ne of the great things about a camcorder is that it can adBust automatically for

di>erent levels of light. It/s very obvious to the 4 when an image is over8 or

under8e%posed because there isn/t much variation in the charges collected on each

photo site. 7he camcorder monitors the photo site charges and adBusts the

camera/s iristo let more or less light through the lenses. 7he camcorder computer

always works to maintain a good contrast between dark and light, so that images

don/t appear too dark or too washed out.

*ormats

+nalog *ormats

3nalog camcorders record video and audio signals as an analog track on video tape.

7his means that every time you make a copy of a tape, it loses some image and

audio 1uality. 3nalog formats lack a number of the impressive features you/ll nd in

digital camcorders. 7he main di>erence between the available analog formats is

what kind of video tapethe camcorder uses and the resolution. 3nalog formats

include:

,tandard VH,#tandard 5+# cameras use the same type of video tapes as

a regular 56. =ne obvious advantage of this is that after you/ve recorded

something, you can pop the tape out and play it on most 56s. @ecause of

their widespread use, 5+# tapes are a lot less e%pensive than the tapes used

in other formatsE they also give you a longer recording time. 7he chief

disadvantage of standard 5+# format is that the sie of the tapes

necessitates a larger, more cumbersome camcorder design. 7hey have a

resolution of about 2'0 to 2;0 horiontal lines, which is the low end of what/s

now available.

VH,-C5+#8 camcorders record on standard 5+# tape that is housed in a

more compact cassette. Fou can play 5+#8 cassettes in a standard 56, but

you need an adaptor device that runs the tape through a full8sie cassette.

@asically, though, 5+#8 format o>ers the same compatibility as standard

5+# format. 7he smaller tape sie allows for more compact designs, making

5+#8 camcorders more portable. @ut the reduced tape sie also means 5+#8

tapes have a shorter running time than standard 5+# cameras. In short
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play mode, the tapes can hold '0 to G; minutes of video. 7hey can hold H0 to

-0 minutes of material if you record in e%tended play mode, but this

sacrices image and sound 1uality considerably.

,uper VH,#uper 5+# camcorders are about the same sie as standard 5+#

cameras, because they use the same sie tapes. 7he only di>erence betweenthe two formats is that super 5+# tape records an image with '0 to G00

horiontal lines, a much higher resolution image than standard 5+# tape. Fou

cannot play super 5+# tapes on a standard 56, but, as with all formats, the

camcorder itself is a 56 and can be hooked up directly to your televisionor

to your 56 to dub standard 5+# copies.

,uper VH,-C@asically, super 5+#8 is to super 5+# as 5+#8 is to standard

5+#: It/s Bust a more compact version that uses a smaller sie cassette.

.mm7hese camcorders use small mm tapes (about the sie of an audio

cassette*. 7he chief advantage of this format is that manufacturers canproduce more compact camcorders, sometimes small enough to t in a coat

pocket. 7he format o>ers about the same resolution as standard 5+#, with

slightly better sound 1uality. 9ike standard 5+# tapes, mm tapes hold about

two hours of footage, but they are more e%pensive. 7o watch mm tapes on

your television, you have to attach your camcorder and use it as a 56. Photo

courtesy #ony,ony Hi-. Handycam

Hi-.+i8 camcorders are very similar to mm camcorders, but there are

several important di>erences. Aor one, +i8 camcorders have a much higher

resolution 88 about G00 lines. 3lso, +i8 tapes are more e%pensive than

ordinary mm tapes.

Digital *ormats

4igital camcorders di>er from analog camcorders in a few very important ways.

7hey record information digitally, as bytes, which means the image can be

reproduced without losing any image or audio 1uality. 4igital video can also be

downloaded to a computer, where you can edit it or post it on the eb. 3nother

distinction is that digital video has a much better resolution than analog video,

typically ;00 lines. 7here are two consumer digital formats in widespread use:

/iniDVPhoto courtesy ewstream.comCanon /iniDV Camcorder?ini45camcorders record on compact cassettes, which are fairly e%pensive and hold

about H0 to -0 minutes of footage. 7he video has an impressive ;00 lines of

resolution, however, and can be easily transferred to a personal computer. 45

camcorders can be e%tremely lightweight and compact 88 many are about the

sie of a paperback novel. 3nother interesting feature is the ability to capture

still pictures, Bust as a digital camera does. #ony has recently introduced
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?icro?5, a format that works the same basic way as ?ini45 but records on

much smaller tapes.

Digital.Photo courtesy #ony,ony Digital. Handycam4igital

camcorders (produced by #ony e%clusively* are very similar to regular 45

camcorders, but they use standard +i8mm tapes, which are less e%pensive.7hese tapes hold up to H0 minutes of footage, which can be copied without

any loss in 1uality. $ust as with 45 camcorders, you can connect 4igital

camcorders to your computer to download your movies for editing or Internet

use. 4igital cameras are generally a bit larger than 45 camcorders 88 about

the sie of standard mm models.

DVDPhoto courtesy #ony,ony DVD Handycam454camcorders are still

relatively rare, as compared to ?ini45 models, but their numbers are growing

steadily. Instead of recording magnetic signals on tape, these

camcorders burnvideo information directly onto small discs. 7he main

advantage of this format is that each recording session is recorded as anindividual track, Bust like the individual song tracks on a 4. Instead of

rewinding and fast8fowarding through tape, you can Bump immediately to

each section of video. =ther than that, 454 camcorders are pretty close to

?ini45 models in performance. 7he picture is a little better on 454 models,

however, and 454s can store more footage. 4epending on the camcorder/s

settings, a disc can hold '0 minutes to two hours of video. 7he newer 454

camcorders support two 454 formats: 45486 and 454863?. @oth are three8

1uarters the sie of 454 movie discsand are encased in plastic cartridges (at

least while in the camcorder*. 7he advantage of DVD-Rcamcorder discs is

that they work in most set8top 454 players. 7he drawback is that you can

only record to each disc once, which means you need to buy new discs

regularly. Fou can record over DVD-R+/discs again and again, but you can/t

play them in ordinary 454 players. 9ike ?ini45 tapes, you have to either use

your camcorder as a player for your 75 or copy your movie to another format.

Photo courtesy #onyThe ,ony 0etwork Handycam $ records onto &oth

/icro/V and /emory ,tick1

/emory card7here are now some digital camcorders that record directly

onto solid8state memory cards, such as Alash memorycards, ?emory #ticks

and #4 cards.

7hese days, you can get a digital camcorder for &H00 and pick up some tapes for

under &)0. 4igital video editingprograms simplify the editing process to the point

where you can master it in an afternoon.


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television professionals is now available as hobby e1uipment. hether you simply

want to record birthday parties and recitals or you hope to produce ambitious video

proBects, the newest camcorders certainly have a lot to o>er.

How Camcorders Work 6 by nafees

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