T356 Week 4 - Spring 2008

• PSA proposals due this week
• Wrap up lighting
• Audio
• Audio / Lighting Quiz next week!
• Demonstration video pitches next week in lab!
• Talk about Demonstration Videos (due next week) and News stories (due the following week)

Readings: don't forget to do the cybercollege readings. Audio units: 37, 38, 39, 40 and 43.

Reality Check:

Next week we'll finish audio and have a lighting / audio quiz. We'll start covering graphics next week. We'll meet here for lecture and have our labs in Geology GY226 (Mon) and Ballantine BH107 (Wed).

The week after next is our News/chromakey exercise. Will cover in lab next week. Students will have to write a 30-second news piece and prepare 2 graphics.

Demonstration Videos - The program proposals and treatments are due in lab next week. Demonstration Video info can be found on-line.

Wrapping Up Lighting

(Finish notes from last week.)

Designing studio lighting plots

For most talent marks/areas, you will need more than one key light. (And with multiple key lights you don't really need much fill.)

Keep key lights off of the set as much as possible. This way you can control them separately from the talent.  (You need proper light placement & set design to ensure you can do this.)

Aim to get around 65-70 IRE for Caucasian skin tones under daylight. (Evening/night scenes or darker-colored skin will target a lesser IRE value.)

Try to get sets and flats about 20 IRE below the talent.

Audio ------------------------

Introduction

Audio for film and video is more than just recording a good signal. Most soundtracks are multi-layered creations that go far beyond providing us with dialogue. We hear cues that tell us where they are- outside, inside, who’s sitting on the left or right, how big the room or environment is. How many people are milling about in the background and what they are doing? Maybe what the weather is like.

You could place two people at a table in a restaurant set and record pristine audio with a $2,000 microphone. It might sound great, but it’s not going to fly with a TV audience. It would sound weird. Viewers expect to hear clinking silverware, the murmur of other diners and music playing over the sound system. A classy restaurant on Friday night would sound much different than a diner on Saturday morning.

In a live studio environment, background tracks must be thought of in advance. The production lab has a library of sound effects and a minidisc recorder. Think of your location and get fitting sound effects and music before you have to produce your project.

Loudness & Frequency

Loudness can be measured in decibels (dBs) and be represented visually with VU meters.

Metering & Level Setting: Analog vs. Digital

• The scale on a VU meter goes from –20 db to +3. We set the levels so most sounds are underneath 0 with the peaks going up into the red area.
• Common practice is to use a 1 kHz tone at 0 on the VU meter for reference purposes. For example we always record color bars at the beginning of tape. It should be accompanied with 1 kHz tone at 0 VU.
• Digital meters are different. The scale starts at around -50 and goes up to 0. When we record the 1 kHz standard reference tone, we do it at –20 on the digital scale. (That's what we use in N America, European communities might use -14 or -18.)
• Just because a meter is digital doesn’t mean it’s for digital audio. Look at the numbering scale to determine if it’s for digital or analog audio.

AGC

Automatic gain control circuits try to get a consistent level. If it’s soft, it’ll boost the signal. If it’s loud it’ll turn it down. Don’t use it! It’ll bring the noise floor up and reduce your dynamic range.

Frequency is measured in Hertz or cycles per second (CPS)

• Hertz = Hz or CPS cycles per second
• Kilohertz (kHz) = 1000 Hertz
• Human hearing generally ranges from 20 Hz to 20 kHz
• Concert A = 440 Hz
• Middle C is 261.63 Hz
• The human voice ranges from about 100 – 9,000 Hz

Impedance = resistance and is measured in ohms. It's important that the output and input impedances match in production gear.

• High impedance = High Z, low impedance = Low Z.
• Professional mics often have an impedance of around 150-200 ohms. Other devices (like electric guitars) can have impedances up in the thousands. You can use impedance matching transformers. (Plug an electric guitar into a microphone input)

Microphones convert one form of energy to another: sound waves to electric energy.

Can be classified in many ways. Most useful are by:

• Electrical characteristics (dynamic, condenser, ribbon, etc)
• Pickup patterns (omni, cardioid, etc.)
• Design (handheld, lavaliere, etc.)

Electrical Characteristics

• Dynamic - durable. Works opposite of a speaker. A coil moves within a magnetic field
• Condenser- need batteries or phantom power. A plate or diaphragm moves adjacent to a stationary, charged backplate. The capacitance between the two plates changes as the diaphragm moves modulating an electric current.
• Ribbon - delicate. A small ribbon moves inside a magnetic field

Pickup patterns:

• Omni
• Cardioid
• Hyper-cardioid (Shotgun) Super Cardioid
• Bi-directional a.k.a. Figure eight

Design:

• Lavaliere (wireless are the norm) Great for TV and film
• Hand held
• Shotgun mic. (Typically used on a boom pole, also known as a fish pole)
• Headset
• Contact microphone/transducer (pickups for instruments)
• Boundary effect or PZM
• Stands (floor & desk) obtrusive good for music; desk: obtrusive but have excellent audio quality (Leno, Letterman)
• Parabolic

Proximity Effect - Sounds closer to the microphone have an exaggerated low frequency response. (Part of the reason radio announcers sound so "bassey" is because they are talking right into the mic.)

Pop-filter - Stops the letters B, P and T from "popping". Typically a thin piece of fabric.)

Phase cancellation - Sound is a wave. When two mics pickup the same sound they will either magnify it if they are in phase, or reduce it if they are out of phase. Reducing the sound through multiple mics is known as phase cancellation. To avoid it assign one microphone s the primary pickup device for each source.

Phantom Power - A way to power condenser microphones over existing XLR cables. Typically 48 volts. Can be generated by mixers and cameras.

Wireless receivers - Diversity have two antennas. Non-diversity have only one.

Balanced vs. Unbalanced (XLR two conductor & ground). Balanced cables have three wires and are far less prone to electrical interference than unbalanced (2-wire) cables. Long cable runs of unbalanced cables will also cause a loss in high frequencies.

Different line levels (+4 dBm & –10 dBm). There are two different levels considered "line level". Professional equipment uses a slightly hotter signal of +4 dBm. Consumer equipment (such as CD players, VCRs, etc) uses -10 dBm. They are usually interchangeable, but plugging a +4 output into a -10 dBm input will sound louder and possibly clip or distort. Plugging a -10 dBm output from a piece of consumer gear into the +4 input of a mixer will usually work fine, except the signal might be slightly softer.

Running cables - Don't run cables adjacent to AC power cords. Keep them separated as much as possible and cross them at 90 degrees at intersections.

 

Audio control booth/production room

Audio Control Booth is used during actual production

Audio Production room is used for post. This is where audio sweetening takes place. Sweetening is the process of adding track & SFX, tweaking eq etc.

Audio console:

Try to visualize the signal flow through the mixer. The audio signal enters at the top- where the preamp is. You can usually select line or mic. Mic levels are brought up to line levels. Really hot line levels are padded (resistance is added to reduce the gain) You don't want audio to clip or distort (make diagram of limited window & square waves)

Next you can have equalization & auxiliary sends (to effects, headphones, sub-mixes)

Lastly there is channel assign (depends on the number of outputs the console has) a pan pot, solo & mute buttons & a channel fader.

Output section contains master outputs for selected channels (eg 1-8 for an 8 channel board)

Boards are usually referred to as 16x2, 16x4. This is inputs verses the number of outputs.

In-line consoles don't use a separate output section. Each input has its own output.

Mix: combine signals

Phantom Power (48 volts) for condenser mics
Patchbay- connect the inputs to the outputs
Digital patchbay & routing (push a button instead of patching)
Calibration: make sure the record level matches the console output (0 vu) Basically make sure inputs match the outputs.

Outboard Gear -

• Equalizers
• Reverb / SFX
• Compressors & Limiters
• Expanders

 

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