Key words: audio frequency, pitch, sampling theorem, decibel, microphones, analogue, digital, recording, additive, subtractive, lens, white balance, exposure, aperture

 

ABOUT SOUND

*audio frequency > periodical vibration whose frequency is audible to humans.Property of sound.

measure> HZ
Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances.
Frequency is the property of sound that most determines pitch.

//: pitch- frequency {. Frequency is an objective, scientific concept, whereas pitch is subjective.}
{. Fequency: the number of times that a wave passes through a given point. Frequency is the number of occurrences of a repeating event per unit time.}
{. High pitched sounds: baby crying, bird calling.}
{. Low pitched sounds: owl, tuba.}
{. Pitch: quality of the sound-low or high-determined by the number of vibration;}

Frequency: is the sound wave; when sound wave is heard itch can be heard; when the frequency is high, pitch is high;
Wavelength and frequency have inversely relationship.When sound wave is low , frequency is high and reverse.

Human ear: 20HZ- 20.000Hz
not below 20 or above 20.000.
not possible hear all the sound in nature
(infrasonic sounds: below 20HZ> blue wales, elephants rumbles)
(ultrasonic sounds: above 20.ooohz> bat/rats-aggressive)
* sampling theorem> sampling is a process of converting a signal into a numeric sequence.The process of reconstruction of a sound that you record in natural environment and then you bring it in a digital form;
{. In digital audio the most common sampling rates are 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz and 192 kHz.}
{. Aliasing:static distortion resulting from a low sampling rate-below 40 kilohertz (Khz).something is going wrong.}
* decibel (dB)> the decibel (abbreviated dB) is the unit used to measure the intensity of a sound.
The decibel scale is a little odd because the human ear is incredibly sensitive.

{. the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB.
A sound 100 times more powerful than near total silence is 20 dB.
A sound 1,000 times more powerful than near total silence is 30 dB.
Near total silence – 0 dB
A whisper – 15 dB
Normal conversation – 60 dB
A lawnmower – 90 dB
A car horn – 110 dB
A rock concert or a jet engine – 120 dB
A gunshot or firecracker – 140 dB
Any sound above 85 dB can cause hearing loss}
{. dB is used to express the ratio between two values of a physical quantity.
used as a measure of gain or attenuation( gradual loss in intensity of any kind of flux through a medium)}

* Analogue and digital recording.
Actual sound waves consist of continuous variations in air pressure.
Representations of these signals can be recorded using either digital or analog techniques.

{. Analogue is when you send the signal in terms of waves; as a series of high and low. the actual representation of what the audio will be.
An analogue wave is a Graphical representation of sound. In order to catch the sound we need to catch the air pressure-what our eat hear.

Analogue recording : Shows you where your voice create this waves that are bouncing back and forwards.
We use a microphone to translate the air pressure to a small electrical voltage> continuous representation of the sound- analogists to the sound.
{Phonograph, magnetophone, Gramophone.}

{. Digital recording will send information as a series of numbers. Requires a clock that measures when to interprete a
a sreis of digital and when to stop. Is made by tiny thousand snapshots:samples.Sample ratio is how many samples per second the digital system takes.The quality depend of how often we take this snapshot and whoch the bit depth is.
44kHZ- 24 bit=compromising between quality adn usability.In order to get the analogue signal from an analogue microphone to the computer I need to convert it in a digital piece of information with an analogue to digital converter. Lower sample ratio or bit-> degretation/noise/distortion }

{. Arguments for analogue systems include the absence of fundamental error mechanisms which are present in digital audio systems, including aliasing, quantization noise, and the absolute limitation of dynamic range.
Advocates of digital point to the high levels of performance possible with digital audio, including excellent linearity in the audible band and
low levels of noise and distortion. }

{. The actual process of digital conversion will always add some noise, however small in intensity.After initial recording, it is common for the audio signal to be altered in some way, such as with the use of compression, equalization, delays and reverb. With analogue, this comes in the form of outboard hardware components, and with digital, the same is accomplished with plug-ins that are utilized in the user’s DAW digital audio workstation)

{. Digital signal is easier to copy, edit, transfer, manipulate, store. when you copy you have less loss of information.
Tascam Dr-05 Portable, Yale Digital Recording Door Viewer etc .}

* Microphone. All micro converts the sound energy into electrical energy.
{. DYNAMIC MICROPHONES: In live sound, nearly all the mics used are dynamics, and in the studio, instruments such as drums, electric guitars, and basses may also be recorded using dynamic mics.
No need of battery or power supply. BUT..the outcome is that dynamic microphones fail to reproduce very high frequencies accurately. In some applications, this isn’t too serious, but if you’re working with an instrument where a lot of tonal detail is contained in the upper harmonics, a dynamic mic is unlikely to bring out the best in that instrument;more gain you use, the more noise you add to the signal;if you’re trying to capture a quiet or very distant sound, then a dynamic mic isn’t likely to produce good results.most effective when working with relatively loud sound sources that don’t contain a lot of very high-frequency detail. They’re also tough as old boots, which makes them good for live work, or for any application within six feet of a drummer!}

{. RIBBON MICRO: Basic ribbon microphones detect sound in a bi-directional (also called figure-eight) pattern because the ribbon, which is open to sound both front and back responds to the pressure gradient rather than the sound pressure}

{. CAPACITOR MICROPHONES:more sensitive, and can capture high-frequency detail much more accurately.}

{ ELECTER condensor mic:Nearly all cell-phone, computer, PDA and headset microphones are electrer types. They are used in many applications, from high-quality recording and lavalier use to built-in microphones in small sound recording devices and telephones. Though electret microphones were once considered low quality, the best ones can now rival traditional condenser microphones in every respect and can even offer the long-term stability and ultra-flat response needed for a measurement microphone}

{. Laser microphones are often portrayed in movies as spy gadgets, because they can be used to pick up sound at a distance from the microphone equipment.}

{ Shotgun microphones are the most highly directional:television and film sets, in stadiums, and for field recording of wildlife.

{ A lavalier microphone is made for hands-free operation. These small microphones are worn on the body.
Originally, they were held in place with a lanyard worn around the neck, but more often they are fastened to clothing with a clip, pin, tape or magnet

{. A wireless microphone transmits the audio as a radio or optical signal rather than via a cable}

{. A contact microphone picks up vibrations directly from a solid surface or object, as opposed to sound vibrations carried through air. One use for this is to detect sounds of a very low level, such as those from small objects or insects.}

{. A throat microphone is a variant of the contact microphone that picks up speech directly from a person’s throat, which it is strapped to. This lets the device be used in areas with ambient sounds that would otherwise make the speaker inaudible.}

{. A noise-canceling microphone is a highly directional design intended for noisy environments. One such use is in aircraft cockpits where they are normally installed as boom microphones on headsets. Another use is in live event support on loud concert stages for vocalists involved with live performances.}

{ VOCALS: inexpensive dynamic mics, rather than capacitor models, because the dynamic mic gives them a warmer, thicker, more punchy sound.}
DRUMS: For drum work, the most common set up is to use dynamic mics for all the close mics/}
(http://en.wikipedia.org/wiki/Microphone)
{ Any mic hears the sound differently: Unidirectional mic only hear what is directly in front of them;omnidirectional pick up sound from alla sides; a figure eight mic hear sound on to distinct sides; for example to record a room full fo sounds you sue an onmidirectional mic.
Also some mic are more sensitive to certain frequencies (frequency response). Also mic color the sound they transmit.This give to the direct sound qualities as “warm”, “clean”, “clear”.}

Preamps: boxes where more than one mic are pluged in..

(THe everything guide to digital hme recording:tips, tools and techniques.)

*EQ and compression: There is only one studio effect that is more useful than the compressor, so useful that it is nearly always incorporated into the mixing console itself – EQ. Equalization is nearly always necessary.
One function of the compressor is to control dynamic range, then a completely separate function is its use as an effect. Take ‘effect’ to mean changing a sound from its natural state into something intentionally different and artificial, either to improve it or simply make it more interesting

{. Compression is used to bring down the highest peaks, above the threshold level, leaving the lower levels just as they were. After that the level is restored so that the peaks are the same level as they were to start with, but the overall dynamic range is reduced. The result is a much more controlled sound.}

{equalisation is primarily about changing signal levels, albeit in carefully specified frequency regions, so pre-compression EQ can alter the gain- reduction action of the compressor, but post-compression EQ won’t.

1. Threshold sets the level where compression starts to take effect. Sounds below the threshold pass through unaltered and only sounds above the threshold are compressed.

2. Ratio sets the degree of compression above the threshold level. A ratio of 2:1 represents mild compression and means that when the incoming level (that is, the level above the threshold) rises by 10dB, the outgoing level will only rise by 5dB. Ratios of up to 5:1 are regularly used for vocals and other instruments, and can pass by unnoticed by the listener if the other controls are set properly. Higher ratios are used for more serious limiting, where the level needs more severe control. Ratios of 10:1 and higher are nearly always noticeable to the listener.

3. Attack is measured in milliseconds and determines the time taken for the compressor to start working once the signal has passed the threshold level. Why have Attack? Because sometimes if you leave just a hint of attack (say, for instance, a snare drum hit, or a powerful downstroke on an acoustic guitar) then it sounds a bit more realistic. Removing too much attack can sound a touch fake.

4. Release sets the length of time it takes for the compressor to return to its normal state once the signal has gone back below the threshold.

5. Gain is provided because compression always reduces the peak level: the more compression, the lower the level of the outgoing signal. This control is sometimes referred to as ‘make-up’ gain because it makes up the level that is inevitably lost during the compression process.

http://www.humbuckermusic.coadeeasy.htm
* DATA COMPRESSION: The process of reducing the size of a data file is popularly referred to as data compression.
Compression is useful because it helps reduce resources usage, such as data storage space or transmission capacity.

1988 H.261 ITU-T Videoconferencing, Videotelephony
1993 MPEG-1 Part 2 ISO, IEC Video-CD
1995 H.262/MPEG-2 Part 2 ISO, IEC, ITU-T DVD Video, Blu-ray, Digital Video Broadcasting, SVCD
1996 H.263 ITU-T Videoconferencing, Videotelephony, Video on Mobile Phones (3GP)
1999 MPEG-4 Part 2 ISO, IEC Video on Internet (DivX, Xvid …)
2003 H.264/MPEG-4 AADVANTAGES OF DATA COMPRESSION:

ADVANTAGES of DATA COMPRESSION.

Less disk space (more data in reality) (*)
Faster writing and reading (*)
Faster file transfer
Variable dynamic range
Byte order independentVC Sony, Panasonic, Samsung, ISO, IEC, ITU-T Blu-ray, HD DVD Digital Video Broadcasting, iPod Video, Apple TV,
2009 VC-2 (Dirac) SMPTE Video on Internet, HDTV broadcast, UHDTV
DISADVANTAGES

Added complication
Effect of errors in transmission
Slower for sophisticated methods (but simple methods can be faster for writing to disk.)
“Unknown” byte / pixel relationship (+)
Need to decompress all previous data (+)

 

ABOUT  CAMERA

SLR: single -lens-reflex

lens: optical element of camera. a curved piece of glass or platic.It takes the beam of the light bouncing off of the object adnr edirect them to come together and form a real image; Light travels quicker through air than through a glass, so lens slows it down.

real image is formed by light moving through a convex lens. The nature of this real image varies depending on how the light travels through the lens. This light path depends on two major factors:
The angle of the light beam’s entry into the lens
The structure of the lens

To increase or decrease the amount of light passing through the lens, you have to change the size of the aperture — the lens opening. This is the job of the iris diaphragm, a series of overlapping metal plates that can fold in on each other or expand out. Essentially, this mechanism works the same way as the iris in your eye — it opens or closes in a circle, to shrink or expand the diameter of the lens. When the lens is smaller, it captures less light, and when it is larger, it captures more light.

Exposure simply refers to the amount of light recorded on the film or sensor. You want the right amount of exposure to capture the image you see (or are trying to create). If you shoot a daylight scene with too much light hitting an overly high ISO sensor for too long, you’ll end up with an overly bright, glaring, unrealistic image. On the other hand, a small aperture at low ISO and short shutter speed could make a daylight scene look dark and murky.

Aperture and f-stop are closely related terms. Aperture refers to the opening in the lens that light shines through when a photo is taken. A larger aperture obviously lets more light through. F-stop is simply the nomenclature that photographers use when discussing different sizes of aperture.
You’ve probably seen beautiful photos of flowers which are close to the camera and in crisp focus, while the background is soft and fuzzy. That is the result of a camera’s limited depth of field. Depth of field can range from extremely narrow (for example, a photo of a flower in which only one petal is in focus while the rest is out of focus) to effectively infinite (such as landscape photos where everything in the image is in crisp focus).
Depth of field is primarily affected by the camera’s aperture setting. As we explained above, a larger aperture (which has a smaller f-stop number) will give you a narrow depth of field, while smaller apertures (with larger f-stop numbers) will result in a large depth of field.

The ISO number is a measure of light sensitivity
While it measures light sensitivity, photographers refer to ISO as the “speed” of the film or sensor. At high sensitivity, more light is sensed within a given period of time than at low sensitivity, so high sensitivity is considered faster. Unlike aperture, ISO settings are relatively straightforward. Low ISO numbers indicate the least amount of light sensitivity, while high ISO numbers are faster, more sensitive settings.

Shutter speed is the third part of the exposure equation. It refers to how long the shutter remains open to allow light through. Shutter speeds are given in fractions of a second — you’ll commonly shoot at 1/500.

White balance reveals an interesting difference between a camera and a human eye: A human eye has a human brain attached. When you look at a white object, your brain is actually interpreting the lighting cues around you and calculating that the object is white on the fly. If the object is under a blue light, it will really look blue, but your brain compensates for the color difference, so you’ll see it as white. The camera does no such compensating unless you force it to do so, so if a white object is under a bluish light, the camera will record bluish pixels.
Adjusting white balance helps force the camera to compensate for the fact that most lighting conditions aren’t perfectly white. Many indoor lights have a yellowish tinge to them, while fluorescent lights have a bluish tint. Even natural light is a little bluer than you might think. You can set white balance manually by adjusting it up or down or selecting the appropriate setting, then taking some test shots to see which ones look most natural.

* Additive colour is colour created by mixing light of two or more different colours. Red, green, and blue are the additive primary colors normally used in additive color system. Additive color is in contrast to subtractive color, in which colors are created by subtracting (absorbing) parts of the spectrum of light present in ordinary white light, by means of colored pigments or dyes, such as those in paints, inks, and the three dye layers in typical color photographs on film.

The combination of two of the standard three additive primary colors in equal proportions produces an additive secondary color—cyan, magenta or yellow—which, in the form of dyes or pigments, are the standard primary colors in subtractive color systems.

http://web.njit.edu/~kevin/rgb.txt.html