DOCUMENT RESUME

ED 074 723 EM 010 896

AUTHOR Stephens, Richard; Hallock, DonTITLE Suggestions Toward a Small Video Facility.INSTITUTION National Center for Experiments in Television, San

Francisco, Calif.SPONS AGENCY Corporation for Public Broadcasting, Washington,

D.c.; Rockefeller Foundation, New York, N.Y.PUB DATE 73NOTE 41p.

EDRS PRICE MF-$0.65 HC-$3.29DESCRIPTORS Broadcast Television; Design Needs; *Electronic

Equipment; Facility Expansion; *Facility Guidelines;Facility Requirements; Guidelines; *Planning(Facilities); Studio Floor Plans; *Television;Television Lighting; *Video Equipment

ABSTRACTDesigned and intended for persons with very little

capital and minimal technical background who are just beginning touse television expressively or expand existing facilities, .this paperdiscusses in detail the basic technical considerations that must bemet before setting up a small television studio. It includes someoperating and design principles, some adaptations of equipment withschematics, and short critiques of certain commercially availableequipment. (Author/MC)

SUGGESTIONS TOWARD A SMALL VIDEO FACILITY.

Richard Stephens and Don hallock

National Center for Experiments in Television

1011 Bryant Street

San Francisco, California 94103

1973

Suggestions Toward a Small Video Facilit

Richard StephensDon Hallock

U.S DEPAR rmENT OF HEALI11EDUCATION 8. WELFAREOFFICE OF EDUCATION

REP R0DOCUMENT HAS BEEN RP',40DUCED EXACTLY 'AS RECEIVED E:ONITHE PERSON OR ORGANIZATIor4INATING IT POINTS 01 VIEW OR OPN

'iONS STATED DO NOT NECESSARILYREPRESENT OFFICIAL OFFICE of EOUCATION POSITION OP POLICY

This paper is intended both for those with very little

capital and minimal technical background who are just begill-

ning to use television expressively, and those with a facility

facing expansion. It includes some operating and design

principles, some adaptations of equipment with schematics, and

short critiques of certain coinmercially available equipment.

It should be noted that the latter information reflects only

the. Center's experience and should be evaluated by the reader

in that light. The Center's video mixing/processing facility,

one of the most important components-of its system, was de,

scribed by its designer, Lawrence W. Templeton, in a paper III,.

cluded in the first Reports series. Audio equipment is not

evaluated here; that is a paper in itself.

I. SYSTEMS APPROACH

If you anticipate expanding your facility at all in the

future, it would be wise to think at the outset in terms of

Richard Stephens was the Center's first maintenance videoneer. His background includes circuit designing and broadcasttelevision equipment maintenance, most recently for the MuzlichOlympics. Don Hallock, a video artist, has a professionalbackground in education and commercial television as a casner4-man, producer and director and was the initial organizer of

the Center's technical/production facility.

2

the entire technical system you plan to have. This does not re-

quire drawing up a detailed long-term purchasing plan, only

realizing that any technical system -- especially Wth the

small., non-broadcast equipment most experimenters use -- cannot

simply be added to quantitatively. If you thLnk only in terms

of single products accumulated bit by bit, it may _become dif-

ficult to integrate these products into a working system. Each

new piece of equipment should be purchased not only in terms

of what it can do for your present needs, but also for what it

can do (or won't be able to do) in the system you'll evolve

over time. What you buy now will affect what you will or won't

have to buy later, and in some cases what appears economical

in the short term may cause you to spend more money in the

future. Several years ago at.the Center, when there wes no mod-

el for an experimental television facility and fewer products

available, equipment was purchased with little thought to sys-

tematic expansion. The result was a mass of cbles and wires

and a system whose real basis was inadequate, most of which

was torn down and the entire facility rebuilt. This is there-

fore being written in retrospect, to help others plan in a

thoughtful way. If you take this approach, there are certain

basic areas we suggest covering in the beginning.

1. Sync Generator (synchronizing pulse generator). If you

would eventually like to have more than one camera, mix

tapes, or mix more than one video source, you should have

a synchronizing generator as a basic component to your

3

system. You will need this to keep parts of the system

in step with each other. The generator provides pulses to

drive the scanning system of cameras and monitors. You

can think of it as the heart of the system (the pulses are

the beats), feeding the beats through the whole system.

Or, another way, as the drummer for your machine band.

In the past, sync generators have been very expensive, but

Sony has a color sync generator selling for approximately

$1000. and Cohn has one for $750. We suggest you bypass

black and white sync generators and, if you can, buy the

color. You'll probably want color eventually, and if you

start thinking in color terms now you'll avoid some pro-

blems later, only one of which is an outmoded black and

white sync generator. A black and white generator cannot

be used to make color video but a color generator will

make black and white. If you know a design engineer

familiar with integrated circuits you can buy a color sync

generator on a chip (Fairchild SemiConductor; #3261DC2)

for $47.00, and for several hundred dollars build in power

supply, interface amplifiers, etc. and construct your own

sync generator.

2. Standards. Certain consumer lines which are very in-

expensive tend not to cc orm to any generally accepted

electrical standards whatsoever. Purchasing equipment

with matching standards is one of the most important keys

to equipment integration for production. This means 1 volt

4

peak-to-peak signal systems with 75 ohm impedances, and

color equipment with NTSC standard. There has been a pro-

blem in the past with half-inch Videotape recorders where,

owing to differences in the diameter of the video head

drum and of the tape speeds, tapes recorded on one manu-

facturer's machine could not be played back on another

manufacturer's machine. The Japanese have recently set

a standard for e VTRs, called EIAJ Standard. All new

half-inch machines conform, but if you purchase .second-

hand equipment and plan to use more than one 2" VTR in

your system, this is something to check. We also recom-

mend linking your system from the beginning with standard

cables and connectors.

3. Cables. Video systems, like any systems, perform best

under certain optimum "loading." In order to maintain

high-performance throughout the system (a crisp picture,

accurate colors, etc.) this has been standardized at 75

ohms, the ohm being the numerical unit of resistance in

certain components to the electronic impulses flowing with-

in the system. It is a unit of "impedance." It is very

important to match impedance values as closely as pos-

sible throughout your system to avoid loss of frequency

response, picture rejection, interference due to reflec-

tion (ringing-echoing in the picture); level losses, and

worst of all, color shifting. There are all sorts of sur-

plus markets that sell coaxial cable, but be sure when you

5

purchase it that it is 75 ohm impedance. One very large

roll of cable, about 1000 feet, is a good beginning for a

system. Specific recommendation: Belden 8281 cable. It

is a bit more expensive than other 75 ohm cables, but it

seems to be standard throughout the industry. The cost

for 1000 feet of such cable will be $200-$250.

4. Connectors. Up to now UHF has been the standard video

connector, and you will find many products considered

broadcast quality that still have these connectors. How-

ever, it seems that industry is now changing to a connector

known as BNC and we recommend starting your system with

this type of-connector. With the 8281 cable and BNC con-

nectors you will be in a starting place where at least you

have matched impedances and have a standard compatible

with other equipment. Where there is equipment at hand

with both kinds .of connectors, adaptors should be kept

handy for ready interconnection. By buying in lots you

will get a definite price reduction. For example, in lots

of 25 they cost 75 each; individually, $1.00. One hundred

of these connectors and adaptors is probably a good initial

purchase for a system. There are two ways to attach con-

nectors: by soldering, or with a connector crimping tool.

If you are planning a system of any size at all, we recom-

mend the latter. The price of.a crimping tool is $75 to

$80; however, it is a one-time investment and makes a

fast, good connection. If you have time, and like to give

6

your gear leisurely and loving attention, soldering is a

mellow pastime, and if you are any good at it it is the

least expensive way to attach connectors.

5. Patch Panel. Even if you have a very small system, you

must have a way to get signals from one place to another.

There are two ways to go about this. You can get a hand-

ful of BNC connectors and make up short lengths of cable

with connectors on each end to connect one thing to another.

But if the system is to become 1aT2ger and have any com-

plexity at all, it is almost necessary to have some sort

of patch bay, a connector-board on which all inputs and

outputs to all major pieces of equipment appear permanently.

This is very simple to build. All you have to think about

is outputs and inputs -- where you want outputs to be able

to be patched and what inputs you' want readily accessible.

All these should appear on the front surface of a panel

fitted with appropriate connectors on the panel which can be

hooked together with a short bit of cable (a patch-cord).

Professional video patching equipment is outrageously ex-

pensive, but the equipment is foolproof and easy to work

with.

. 6. Used Equipment. There are some companies' which special-

ize in second-hand equipment, and these can be scouted.

Buying used video gear has the same pitfalls as buying

second-hand cars, toasters or anything else: it may help

you to have someone with expertise to advise you on the

purchase. Other places to check are local broadcast stations,

both public and commercial. Often they have discarded equip-

ment, patch bays (the Center's came this way), cable, all

sorts of things. If you can rummage through their outmoded

equipment you may find that what is outdated for them is

quite appropriate to your needs. YUU can remind them it is

a tax write-off, as well as a gift to be noted in FCC

license renewal applications.

II. PHYSICAL FACILITY

The physical situation into which you put your equipment

is obviously more than a space, and unless you are well endowed

there are compromises that must be made. But if not chosen

carefully, the physical space can become a burden, and you will

spend part of each production session working around built-in,

'unsolvable problems rather than putting your energy creatively

onto videotape in the form of images. You will also spend

money. The Center has moved three times in its history. .A.-!re

are some of the parameters we have found useful.

1. Power. Start with 200-300 amps of power. Initially

the power requirement will be small, but this is an important

place to consider the future; video products, particularly

lights, require a great deal of power which adds up very

fast, and if you begin with 100 amp service, it may be dif-

ficult to add more later.

2. Heat. If you can choose your building, get one with

as high a ceiling as possible (12 feet or more). The

8

reason for this has less to do with space than the fact

that lights produce an inordinate amount of heat, which

becomes very uncomfortable for you and for your equipment.

Evenness of temperature is very important; try to make your

room temperature 60° to 80°. This is a much wider range

than most broadcast stations maintain. They are controlled

at about 70° to 75°, which is ideal. Watch overheating.

Equipment tends to drift (change its behavior) quite a bit

if it heats up, particularly the transistorized, solid-

state equipment experimental facilities have.

3. Dust. Your room should be as dust-free as possible.

We would not recommend a room that opens out onto the street.

Dust is probably the most damaging element to videotape: it

degrades quality rapidly and sends your raw stock costs

skyroCketing. The mechanical systems in videotape recorders

are also sensitive to dust. Electronic systems in general

can short because of dust, and dust mixed with humidity

produces alternate paths for electrons and can cause actual

electrical breakdowns.

4. Physical Layout and Cabling. Your production space

should be large enough to house all your equipment plus

all your fantasies. The size of this space varies with

the kind of work you intend to do -- working with several

freely moving dancers will obviously take more than a sim-

ple set up for electronic feedback. The more equipment you

can put on wheels -- on rolling tables -- the more flexible

9

you'll be; you can put together unorthodox arrangements of

equipment, which is a basic part of experimental work. If

you have very little equipment, there's no

at the beginning, but as your gear becomes

need to do this

more profuse,

it saves you and your time (an Ampex 1" tape machine weighs

approximately 90 lbs.) The patch panel is central here,

having a main connection point so that you can patch sig-

nals around without physically having to reconnect all your

equipment. When cabling your facility try to put the cable

overhead or otherwise out of the way. Roughly divide the

space so that you have your tape machines in one area,

your mixer in another, your camera arrangement in another.

They needn't be separated by a great deal of space. First,

figure out how many lines you need, and give yourself a

few extra ones. Allow 6-10 feet more cable than you think

you'll need for monitor lines and such things. Invariably

you'll need that few extra feet at some point. You can

always make a few loops with the excess cable and hang it

onto something. Labe/ the wires, then decide on some means

of ducting or bundling cables. If you have the time you

can do trench work in the floor or ducting around the walls,

or you can take the group of cables which is likely to come

from the mixer and patch panel and run them overhead on a

grid made out of pipe to the various tape machine camera

and monitor areas. You thereby avoid masses of line on the

floor, tripping over cables and toppling monitors, and the

10

maintenance problems that come with injured cables. The

grid can also be designed for lighting. Monitor Loops. If

you have just a few monitors you can leave wires connected

to them all the time. If you have a situation where you

are going to want extreme flexibility and quite a few moni-

tors and have a fairly large area to service, then it's

wise to run monitor loops, two pieces of coaxial cable

going to each place where there's likely to be a monitor

or monitor *area. One serves as an input line and the

other as an output line and you can feed your signal into

one monitor, out of it, back to the, patch panel and then

into another monitor and out of it and back to the patch

panel, etc., stringing a group of monitors together with-

out having to reconnect them physically, and terminating

them in the patch panel. Systematic cabling is not only

facilitous and straightforward for production, but when

something breaks down you have a set of "knowns," and can

spot the trouble almost immediately without having to take

a pitchfork to a pile of wires.

5. Las. Keep a log of your technical system. Write down

what connections were made. As each cable is connected,

put a label on it stating where the cable has come from

and where it is supposed to go. This will save no end of

trouble when cable gets tangled. (Masking tape is not a

good idea; it rips off easily and the writing gets worn

off with use.) Number each cable in the house (you can

11

buy print stick-on labels) and transfer that

cable nu: a log. You then have a r, 1rd of your

system which will help in troubleshooting and will also

show you how and where to expand the system.

6. Floors, Walls, Worklights. Floors should be smooth,

particularly if your kind of work involves dollying cameras.

Cement floors are hard on the feet and legs for long

stretches of work, but this can be somewhat alleviated by

patches of carpeting in parts of the working area, such

as the videotape editing area, where production tends to

go on for hours. The floor should be solid, especially if

you are sharing a building with any sort of industrial

company and/or you're located on a street which has heavy

truck traffic. If the building vibrates at all and you do

any sort of semi-precise camera work, your production hours

will be limited to the middle of the night, holidays and

weekends. Often for financial reasons it is sensible to

rent space in a warehouse or light industrial area. Try

to choose a building where you can make noise, but not one

which will subject you to a great deal of it. Walls and

ceilings of the room which has cameras and lights should

be painted black or some other very dark color. If not,

you'll get bounce light splashing off the walls and ceil-

ings and reflecting off the monitor which will not only

prevent your truly seeing what you're putting on videotape,

but also will actually alter feedback patterns on the

12

monitor as you move around the room. For this reason, flat

overhead lighting is not good; each area should have its

own carefully controllable illumination. Artists' video

is basically dark room work; the light you deal with in

your final work is light radiated off the monitor, your

frame is black infinity.

III. CAMERAS

The following is an evaluation of the cameras the Center owns

and some suggestions for broadening their abilities:

1. SankLL7-.L-3Zf00AVC-3/209),. There are several

good black and white cameras on the market for studio use,

ranging from $700 - $1,300. However, for a first camera

it is not necessary to spend that amount. Sony Corpora-

tion makes a product which they trade-name Portapak at

$1,500. Portapak is a very small hand-held black and

white camera with a 4 to 1 zoom lens, and a very small

half-inch black and white videotape recorder. The two

units are integral; that is, the VTR has in it its own

battery pack, and it also has the option of being plugged

into a small AC-to-DC converter. The camera plugs into

the VTR and thus derives its power from the VTR. To use

the Portapak camera alone as a studio camera, you can build

yourself a small converter box that will supply power as

well as standard television drive signals and reconvert

those signals into drive pulses that will drive the camera

to make scans. This will cost about $30 in electronic

13

components; the schematics (C) are attached at the end of

this paper. You will then have one camera that will func-

tio7 almost as two; alone for studio use, or with the VTR

AS a stable remote camera.

Richard Stephens has also designed a very simple cir-

cuit that allows one to monitor the output of the Portapak

VTR without looking into the Portapak camera viewfinder.

As the Portapak system comes from Sony, the only way to

monitor tapes is to look back into the camera, viewfinder

(about luxle) and play back the tape. This is most un-

satisfactory if you want to see what the picture will look

like on a bigger monitor. For about $1.50 you can build

a very simple circuit that allows the signal to appear

on any monitor. This schematic (B) is also attached.

In addition, Sony makes a small television receiver

(model 710U, $165.) that receives only air pictures, but

again, for an investment of about 85c you can cable in

through BNC connectors and access the video circuitry so

that you can use this television receiver, as a monitor,

one that weighs only a few pounds and can become part

of your remote Portapak unit.

For about $2.00 you can put a transistor circuit into

Sony Portapak cameras which will allow the operator to have

control over the video gain. This means that you can use

that circuit to fade out video pictures to black, a much

smoother transition than just turning the camera off. You

14

can fade in from black and fade out to black as-you shoot.

Control of gain when doing video feedback is important, and

you can increase the gain over the full range of video with

Zis adaptation. (Schematic A, attached.)

2. Sony AVC-3200. This is a studio camera and costs about

$700. If you do not need the Portapak VTR, the AVC-3200

is a more versatile camera than the Portapak camera. It

is a simple instrument which has no level control, but it

has a detachable viewfinder, a 4 to 1 zoom lens, selection

of internal and external sync which means it can drive it-

self or be driven by other equipment in the system. (To

drive more than one camera in sync a separate sync generator

is necessary.) There is a coaxial cable output on the back

of the camera which is separate from the camera cable.

With the camera cable, you get back video which you can

plug into your mixer or your tape machine. But you can

also run a second output of video -- a composite video

signal -- which you can take directly to monitors. There

is a selector switch on the camera which switches that

coaxial connector from a composite video signal (one which

has sync pulses) to a radio frequency signal which will

drive a regular TV set when connected to the antenna termi-

nals.

3. Sony DXC-2000A. (no longer available). This is a good

camera because it uses a 3/4" Vidicon rather than the

newer 2/3" Vidicon. It gives higher resolution than the

15

Portapak or AVC-3200 and it is a slightly heavier camera.

It also has a few more adjustments that sometimes make it

more flexible. The 2000A has gain control, aperture cor-

rection and gamma correction. It also has pedestal

lev ls, sync levels, video level, and they can all be ad-

justed very simply with a screwdriver. The Portapak

camera, on the other hand, is a compact piece of equip-

ment which is a bit difficult to get inside of to make

any adjustments. All these cameras must be partially dis-

assembled in order to make the more sophisticated adjust-

ments.

4. Sony DXC-5000 color camera. This camera works quite

well when in proper adjustment and comes with a color sync

generator. It costs $10,000. Most of the current work

done at the Center uses black and white images as sources

to be processed through a color video mixer or video syn-

thesizer. You might evaluate this mode of working from

both an artistic and financial standpoint before you de-

cide to invest in such a camera.

IV. VIDEOTAPE RECORDERS

Matters tend to become rather ambiguous in this area.

There are quite a few VTRs on the market and no single machine

answers all needs. If the budget allows, however, one should

purchase a color machine. Color tape machines will record

superior black and white imagesas well, and you will have

the VTR available when you want to move your system into

16

color. In addition, any tapes you have recorded previously

can be played back on that machine and you can use your old

black and white tapes as image bank material.

Half-inch quality on playback is probably as good as a

home color television receiver. The other extreme is two-inch

quadraplex tape which is broadcast standard and into the

$100,000 range. One inch is, in quality, about half the way

between half-inch and two-inch. Another difference in quality

is pointed up by how many generations of videotape you can

go before the quality is unacceptable. By the time you get to

third generation on half-inch -- the copy made off a copy of

the original master tape -- the picture is quite degraded in

quality. On one-inch machines you can usually go to the

third generation and maybe have quality that equals the first

generation of half-inch. And on 2" you can go many more. What

follows is an evaluative rundown of the videotape machines the

Center owns or has owned.

A note on color. Ampex one-inch color electronics are extreme-

ly good. One can put. down flat fields of color or fields of

really doubtful kinds of color that tend to confuse a machine's

circuitry because they are neither fish nor fowl. As in paint-

ing, artists mix colors in video, and the machines must some-

how reconcile all of the bits of different color used to make

up each single "color." Videotape recorders are made general-

ly to record "broadcast" color, which is very thin, with little

contrast or saturation. While Ampex machines are best able to

17

reproduce the sorts of color artists mix,thtay have difficulty

when the saturation level is high, as any videotape machine

does.. Sony electronics are less able to reconcile these

color-mixes well without breaking up I ,oilich is made

up of the separate components of that color. Saturated pur-

ple, for example, which is difficult enough for a 2" broad-

cast machine, is almost unusable for a video artist working

with smaller Sony machines because it turns out as red and

blue noise. Sony machines have other redeeming features, how-

ever, and all of these factors must be considered before pur-

chasing one to suit your particular needs.

1. Sony 5000 and 5000A. These are half -inch color machines

which Sony no longer manufactures. The letter "A" signifies

that the machine has a noise reduction circuit that pro-

cesses the color signal to produce a sharper picture. In

our experience at the Center Sony has offered the most in

half-inch machines, although the newer Panasonic machines

are reportedly even better. The 5000 and 5000A have given

little trouble in terms of maintenance, and they get a

great deal of use. The 5000A is a very good workhorse.

It is a machine that will not give you 2" picture quality

but it will, more often than not, give you a picture.

Sony uses two video heads, instead of one which gives a

somewhat better picture quality.

The circuitry does tend to drift over time, so the machine

needs regular calibration, and every so-many-hours it is

18

necessary to sit down and go through the maintenance pro-

cedures and tune up the machine. Sony s service ma b

are very good.

The audio circuitry on the 5000 and 5000A is poor. The

frequency response is only adequate and the gain or level

of the recorded signal is automatically controlled. This

means you have no control over levels unless you rebuild

the circuitry. The Automatic Gain Control, or AGC, is

intended to make recording efficient, but instead it re-

duces the dynamic loudness range of your sound track and

increases the alwayspresent buzzing so that there will

be noise in quit sound passages.

2. Sony 320F. The 320 is Sony's one-inch machine. Some

people rave about the 320. It lives up to the Sony's work-

horse rlzputation and has been able to take a great deal

of abuses along with a great deal of use. Unlike Ampex l"

machines, there are no mechanical problems, but it does

have many difficulties in its color recording. It is

better than the half-inch, of course, but compared to the

Ampex 1", for instance, has more color noise and poorer

resolution. The audio is satisfactory except for one thing

-- it is made to record broadcast standard level audio.

This mehins that home hi-fi gear, which is what most of our

audio wst:m is composed of, will not drive that record

circuit properly. In other words, if your input level

is the consumer pro4ucit level of -10d14 it will play back

19

a very weak recording. Broadcast level is +4 or +8db,

and that is what Sony's 320 is actually made to record.

If you cannot drive things that high, you'll have trouble

with weak recordings. What the Center did with its 320

was to change the input attenuation so that it became

compatible with home gear. The Center has sold its 320;

there was a moire pattern in the video recording which

no one, including Sony engineers, seemed to be able to

eliminate.

Ampex 1" VTRs. Ampex machines make high quality video

signals but require careful and steady maintenance. If

you have a person to do this, you will get the best quality

with Ampex machines. Ampex has a single-head system, one

video head on the machine, where Sony has two. However,

the writing (record-scanning) speed is very high -- 1,000

inches per second -- thus giving high resolution, low

noise recording in both black and white and color. Ampex

also has a high-band carrier frequency system which pro-

duces very high quality color pictures.

3. Ampex 7000. This is the Center's, first VTR, a black

and white machine. It receives little use now, and there-

fore has given few problems.

4. Ampex 7500. This is a color one-inch machine. It is

used regularly and breaks down regularly. One of the pro-

blems the Center has experienced, however, is that the

demands on a maintenance engineer's time are so great that

20

a regular schedule of two to three hours a week of adjust-

ment procedures per machine cannot be followed. The Cen-

ter's 7500 is a model that fits down into a case and as a

result, the circuitry is not accessible unless you un-

bolt it from the case and lift it out. We suggest with

this model cutting off the front of the case to slip the

front part of the machine down. This accesses the most

important circuit boards which are the servo board and

the mod/demod circuit.

5. Ampex 5800. The Center bought this machine for good

editing capability. The Sony 320 does edit but the edit

circuitry was not high quality and often would produce

flashing and glitches at the edit point. The Sony system

uses a flying erase head that erases a video track and

lays down a new one; sometimes the edit erase will not go

in at the proper point. The Ampex 5800 has another good

feature, an external sync input; that is, you can take

synchronizing signals from your generator, put them into

a VTR and by doing so, any edits that you make are started

and completed only during the vertical blanking interval,

and this makes the edit clean.

6 Ampex 7800. This is a one-inch machine that is almost

a two-inch machine. That is, it has all of the features

that two-inch machines have -- sync inputs and sync out-

puts, blanking inputs and blanking outputs, editing, ac-

cessible circuit boards that pull out and can be put on

21

extenders; and logic controlled tape handling: fast rewind,

fast forward, start, stop and slow motion circuits. Tape

handling is practically foolproof. For example, if you

are in fast forward and hit the rewind button accidental-

ly, rather than ripping up your tape (as the 5800 and

earlier Ampex models will do), the machine reads your com-

mand and decides whether it's in a mode that's sensible

for answering that command. Since its range of choices is

really very small, it can decide easily whether what you've

just told it to do will destroy the tape. And if it comes

up with the answer, "yes, it will destroy the tape," then

it simply comes to a discreet stop and waits for you. In

addition, the 7800 has a remote control box which you can

put on your mixing console so that you can start your re-

cording, edit, and stop the machine from there as you're

making your images, rather than having to get up, go a-

cross the room and come back to your mixing area. The

video quality is excellent.

7. Sony Videocassette. This is basically a consumer pro

duct and as such has limited usefulness as a professional

or semiprofessional tool. The 3/4" tape is completely

enclosed within the plastic box, and there is no access to

it except to break the plastic box, which then makes it

impossible to play the tape. When you press the start but-

ton, it takes 5 to 7 seconds before it actually shows a

picture because the tape has to be physically pulled out

22

of the cassette by a little finger and drawn around the

drumhead, which is inside the machine. The inaccessibil-

ity of the tape means it can't be physically spliced. The

tapes themselves are limited to half-hour and hour format,

and you can't shorten a reel. The cassettes are easy to han-

dle physically since they are self-threading in the machine;

interchangeability of playback machines seems to pose no

problem. The cassettes are most useful for playing hack ex-

tended segments of one minute or more. Cueing is dif-

ficult because of the complicated mechanical processes in-

volved, and because the linear tape speed is much slower

-- 3 3/4 inches per second -- and fast forward and rewind

are therefore very fast. We do not consider it to be a

mastering machine. The picture quality is good, as is the

color (that is, nearly as good as IVC 1", better than

Sony 1", but nowhere near Ampex 1".) Because it is in-

tended for home use, the audio circuitry in general and

the audio AGC in particular, create real problems for the

video experimenter; the Sony reel-to-reel machines such

as the 5000 are intended for the inexperienced but some-

what knowledgeable amateur who is making his own tapes.

The cassette machine, on the other hand, is made for the

consumer with no technical knowledge who wants a machine

that will work dependably and well with the least amount of

effort on his part. The level control circuitry in the

cassette machines must therefore cover and control a wider

23

range of level fluctuations; in experimental use, however,

the machine tends to control you, rather than the reverse.

For example, it is impossible to record and play back si-

lence on a 3/4" machine. The audio AGC has an incredible

gain factor so that if you have twenty seconds of silence

on your tape, by the end of that time all your line-hum

and tape hiss will be amplified to a literal roar. Obvious-

ly this cuts down your production freedom. The AGC also

tends to destroy the dynamic range of your sound track:

a soft, quiet passage of sound in your piece gets pulled

up to full level; and if you decide to really lay it on

thunderously, the machine will simply turn you down smooth-

ly so that your cresendo becomes the same loudness level

as all the rest of your scores If you plan to use the

Videocassette in most production situations, you will have

to go into it and remake the audio circuitry.

V. MONITORS

In the beginning stages of a system, the less expensive

monitors are adequate. You can always rent a good monitor to

display work made with good tools, but if your basic video

system -- cameras and videotape recorders, particularly -- are

of unsatisfactory quality, your picture will look poor even on

the best monitor available. The least expensive display sur-

face is a television set with an RF converter that allows you

to plug in your 75 ohm video picture and receive back something

you can connect to the antenna terminals of the set and so see

24

the picture through it. The converter is a tiny television

broadcasting station in a box which you connect to the set's

antenna terminals because a regular set will not read a video

signal fed into its antenna. For that you need ...a carrier

frequency. The box gives you a television picture with that

carrier frequency. The problem with these "jeeped" monitors

is that they do not have the circuitry to produce a true black

field (zero luminance); their "black" is medium grey. Any

picture that uses subtleties of light and dark compositionally

will therefore lose its nuances on such a monitor.

A step better than this is a manufactured monitor such.

as Panasonic's or the Sony Trinitron. These are semi-profes-

sional monitors which include monitoring circuits built on the

basic chassis of a television set. The Trinitrons are excel-

lent. Broadcast stations use them in parts of their facility

where Conracs,.the best monitors available, are not required.

The monitor also receives transmitted broadcast signals so you

can record off the air. It is integrated with the Sony half-

inch VTR gear so that you can feed directly into the tape

machine what's coming into it from a broadcast station, or you

can feed directly out of the VTR into the monitor for a com-

pact playback set-up. A 14" Trinitron color monitor is about

$400; it will render excellent black and white pictures, and

seems to us to be the best multi-purpose means of display

available now.

25

VI. ACCOUTREMENTS: LIGHTS, LENSES, TRIPODS, VIDEOTAPE

Obviously, the kind of lights you need depend on the sort

of work you do. The work at the Center involves precisely

controlled amounts of light on very small areas; for this

photographic and theater lights and spots are used; Fresnells,

Lekos (ellipsoidac reflector spots) quartz-lights, etc. If

you can manage to find three of four 1000 watt Variacs or 5000

watt Variacs you can have dimmers and good control. You will

probably have little use for film floodlighting such as the old

Colortran products.

Your choice, of lenses, too, depends on your aesthetic.

Basi.ally, you have a choice between fixed lenses and zoomar

lenses. Most Sony cameras come with a 4:1 zoom lens, nota

great range, but adequate. In this day and age of zooming, fixed

lenses are greatly undervalued. The zoom lens is actually a

master's tool, deceptively easy, which to be at all successful

as a lens must be used with a great amount of sophiscation. You

can also get fixed lenses in wider and longer focal lengths than

most zooms are capable of producing. For video, any decent

quality 16 mm lens is acceptable; 16 min film is capable of much

higher resolution than video cameras, so anything that works

well for a 16 mm film camera will be fine for a C-mount tele-

vision camera. The television screen does not intrinsically

require that human scale be a referant for size, and a set of

close-up lenses and extension tubes may be a very sound pur-

chase for your work. The best zoom lens available and the

26

most expensive is the Angenieux 10:1 zoom, $900. Others can

be acquired for less. Surplus dealers often have used

optics.

Good tripods are not inexpensive. You should be able t

pan and tilt your cameras smoothly, and even roll them over on

their sides. Still camera tripods are intended to be set up

and locked in place and no not have smooth tilting mechanisms.

There are panhead tripods which are countersprung to offset the

weight of the camera and ones with smooth action, some of them

viscous damped with a silicone substance, some of them geared,

so that you can pan and tilt them with great smoothness. The

old-fashioned wooden tripods have a geeat deal to reconuend

them, but their legs are not easily extendable and retractable.

Those with a column that cranks up and down in the center are

good; the cheap aluminum tripods with turn collars on the legs

give a great deal of trouble.

With respect to brands of videotape, we cannot recommend

one over another. They are all exhorbitantly expensive. The

new carbon-backed tape such as the Memorex Chroma 80 an Ampex

162 is good except that it is difficult to mark on the back

with a magic marker for edit cueing. There is a new high

energy tape thatrequires special settings of the machine,

but the Tecordings tend t6.fade ( loose strength) after a while.

One can buy:used tape from companies like DAK Angeles;

it is:probably used computer tape, half the price of new

tape stock; it can be used to make sketches for your final work.

27

This has been a brief and cursory appraisal intended for

readers with little technical knowledge. A more precise papen:

would run many times this length, and an evaluation of the

products availat e and adaptable to experimental use would be

a small book, one rendered almost tmmediately obsolete by the_

rapidly changing and very complex electronics industry. One

entire area upon which the quality of any system depends -- the

proper maintenance of electronic equipment -- has been omitted

because it is nearly impossible and probably impractical to

translate for non-technical readers. We would be glad, however,

to answer any questions, expand on any areas, or detail any

points covered in this paper by letter. A final word: an

electronic system is not just a means to produce images or a

vehicle for ideas; it is a very beautiful, complicated, simple,

and illuminating balance of power and energy. You, and in a

very real sense, the image possibilities you have, are enrich-

ed if you understand its flow, its substance and its connections.

APPENDIX

28

The following are descriptions of some basic andvery simple modifications that can be made to theSony Portapak (camera & VTR).

(A) First is a description of a video gain control thatcan be easily added in a few hours and at a cost of$3-$4. With such control, one can adjust the amountof video from zero to full output while allowing thesync signal to remain constant and therefore allow-ing a stable output at any of the ranges.

(B) The second modification is the addition of a monitoroutput to the Portapak VTR. This will allow one tohook any standard monitor onto the VTR for preview-ing recordings and playback of pre-recorded tapes.This circuit modification will cost another $3-$4but is far less expensive than the rf monitor op-tion that Sony sells for the VTR.

(C) The last modification is one that will allow thePortapak camera to be divorced from the VTR so onecan then use the camera just as any other studiocamera would be used. The "interface" box in-cludes drive conversion, (this modification pre-cludes the addition of a standard sync generatorto your TV system.) video processing and a powersupply. By far this is the most expensive modules$25-$30, but is very much worth doing if onewould like to use the camera in a studio situation.

If there are any questions concerning these mOdifi-cations please feel freeHto contact NCET.

Richard Stephens

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Richard Stephens

NCE.T1972

Notes

I. All capacitors are in micro-farads unless otherwisespecified.

2. All resistors are in ohms, '' /.Wunless otherwise specified.

3. The symbol indicates acomponent whose value is

selected to yield specifiedoperating conditions.

4. Blue numbers arc DC volt-ages, measured from pointindicated chassis with VOM aand with no signal imput(lens cap in place)

SONY® VIDEO CAMERA

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,Figure 5 Prototype Direct' Video Synthe- Figure 6 View.of Control Panel.sizer.

Photo credit: M. d'Hamer.

Direct Video: An Electronic Artform for Color TV

S. C. Beck

National Center for Experiments in Television, San Fiancrsco,

Introduction

Within mankind's tools are latent prop-erties which often remain unutilized. Tele-vision is no exception. As an electronicsystem its range of impact and complexityare astonishing, more so than its usual con-tent indicates. It is possible, however,.to go one step further than televisionmight seem to permit and remove the TV cam-era, replacing it with electronic circuitswhich can be manipulated to effect the for-mation of an image on a video monitor.This is direct video synthesis, an elec-tronic means of evoking images from withinthe television system. It presents thevideographer with -a method of using tele-vision as a medium of personal expression.(Fig. 1 to 4)

Genesis of the Direct Video Synthesizer

I was-led to color television in thesearch for a precise, electronic means forexpressively controlling light. Many graph-ic displays which are available seemedcostly and neglected a common piece of dis-play hardware -- the color television set.Hence arose the notion of a visual synthe-sizer, designed to display directly in acolor video format. It remained, however, .

to formulate an aesthetic model upon whichto base the engineering of image-formingcircuit modules which would constitute thesynthesizer.

Aesthetic Model

The synthesized image is built up ofparallel (in time) layers of image informa-tion. An image is modeled to consist ofeleMents of form, motion, texture, and col-or. (A mathematical development of form aspoints, lines, planes, and perspective il-lusions serves as a preconditiOner for elec-tronically realising this element in two di-mensions.) The temporal change of geometri-cal relationships between elements of formgives rise to motion. Texture arises inseveral manners; for example, as brightnessgradients over elements of form, or as ag-gregates of microforms, and also dynamically.The spectral distribution of reflected andradiant energy of forms evokes color fromour perceptions.

Implementing the Model:Outline of the Synthesizer

Mapping from the aesthetic model intoreal electronic control of video images issummarized here:.

1) sequences cf pulse-width modulatedsignals are developed which definetwo dimensional contours of formover the monitor surface;

2) waveshaping and amplitude modula-tion of these signals allows con-trol of the brightness gradient,yielding texture;

3) proportional distribution of thesesignals as excitation for the pri-mary pigments of emitted light, red,green, and blue, produces a gamutof colors with hue, saturation andluminance specified precisely.

I have co:Istructed a prototype synthe-sizer (see Figure 5) utilizing this processwhich consists of circuit and control mod-ules that function directly on a scannedraster basis. A controlled-voltage parame-ter approach has been employed to direct theimage element producing modules. Thus, acomputer can be used to generate controlvoltages, but, more importantly, the video-grapher has. intimate control of the imagethrough various physical-to-control voltagetransducers. (I hope to include bioelec-tronic transducers also.)

Operation

By patching desired modules together atthe control panel of the synthesizer, as inFigure 6, and supplying appropriate controlvoltages to control ports a given passage ofimages may be executed. Some modules gen-erate and manipulate forms,' while other mod-ules impart differing textures to forms, orindependently control the various layers ofthe total image. Camera signals may be pro-cessed through the synthesizer also. (Fig. 4)

The synthesizer accepts video sync anddrive pulses as "Backdoor" inputs and deliv-ers parallei'RGBY (red, green, blue,, lumi-nance) outputs to the video encoder. This

makes it possible:to use the synthesizer withvarious video formats by substituting syncgenerators and encoders, an important ele7ment of flexibility. The present version pro-duces NTSC compatible color: video.