Blackboard only

Because much of future posts will refer to Blackboard resources, you should read the course blog on Blackboard. Those posts will no longer be duplicated here.

The Thing in the Basement blog is on hiatus until further notice.

RTFM: Digital Photography

See the blog entry on Blackboard for details, including links to Course Materials.

Study checklist for Digital Photo lab practical

___ Digital still camera __ good batteries __ External hard drive

___ Check batteries__ imaging file format__ image resolution__ data cleared__

___ Disable flash__, set camera to “Easy” settings__

___ Position camera to compose subject level & square__ and using rule of thirds__

___ Press shutter button halfway to lock settings__, then press rest of way to take picture__

___ Use LCD screen to review picture

___ Change ISO to lowest number__, shutter speed to 1/30 second__, f-stop to lowest number__

___ Set Autofocus On

___ Position camera to compose subject level & square__ and using rule of thirds__

___ Press shutter button halfway to lock settings__, then press rest of way to take picture__

___ Use LCD screen to review picture

___ Change ISO to highest number__, shutter speed to fastest__, f-stop to highest number__

___ Set manual focus for moving object’s path__, position camera to capture moving subject__

___ Press shutter button halfway to lock settings__, press rest of way to capture moving subject__

___ Use LCD screen to review picture

___ Move image files from camera to day’s folder on external USB drive

___ Open images in Photoshop

___ Check focus__ and noise__ at 100%

___ Check level/square__ at Fit on Screen__, and repair with Ruler tool and Image Rotation|Arbitrary__

___ Try Auto Tone__, Auto Contrast__, and Auto Color__; if no improvement, undo each

___ Crop images using Rectangular Marquee tool|Image|Crop

___ Save As TIFF to external hard drive

Digital Photo Basics

Sensor = the part of the camera that responds to light; equiv. to film

pixel = contraction of picture element, one dot on screen or sensor

resolution = width x height in pixels

megapixel = 1 million pixels

ISO = sensitivity (50, 100, 200, 400, 800, 1600)

Metaphor of filling a bucket from a faucet:

ISO is the size of the bucket to be filled

aperture or f-stop is the size of the faucet opening

 (how far you turn the handle)

light level is the water pressure coming out of the faucet

shutter speed is how long you keep the faucet open

Overexposure (too light) = bucket overflows

Underexposure (too dark) = bucket isn't full enough

Given a light level, what ISO, aperture and shutter speed will fill the bucket?

ISO too high = video noise (film grain), too low = underexposed

Keep the ISO as low as possible; only raise it when the best other settings are still too dark

Shutter speed needs to be 1/30 second or faster to freeze action.

Faster action needs higher speed. Too low shutter speed makes motion blur, especially handheld

Depth of Field/ Depth of Focus = DOF = distance from closest sharp focus to farthest sharp focus

Pinhole aperture = maximum DOF (Flip is a pinhole camera with a fixed lens)

Wide aperture = shallow DOF

Shallow DOF is good to emphasize subject, deemphasize foreground and background; shallow DOF requires more attention to focus, usually manual focus

Low light requires wide aperture, which gives shallow DOF; if you need deep DOF, you need more light or a higher ISO

File formats: JPEG lossy, RAW proprietary, TIFF lossless but large, PNG lossy

RGB red, green, blue color channels

24-bit color is 8 bits (256 levels) per color channel

Digital Audio

Sound is analog. The sound of a guitar string being plucked is a smooth, continuous, curved wave, close to an ideal sine wave.

The pitch or frequency of sound is measured in Hertz, Hz, or cycles per second (cps). Humans can normally hear sound in the range of twenty to twenty thousand cycles per second, 20 Hz to 20kHz (kiloHertz).

Digitizing (or quantizing) means taking a series of measurements of the sound wave, and converting those measurements to a series of numbers.

Digitizing requires samples to measure. Sampling accuracy determines the fidelity, or how closely the digitized data resembles the original sound. Sampling accuracy depends on the frequency or sampling rate (how often a sample is taken), and bit depth, or how accurately each sample is measured.

The Nyquist limit states that the sampling rate must be at least twice the original sound frequency. To accurately digitize the highest pitch humans can hear, 20 kHz, the sampling rate must be at least 40 kHz. The sampling rate for audio CDs is 44.1 kHz; camcorders usually sample at 48 kHz. The lab's R-09HR recorders can sample up to 96 kHz. The higher the sampling rate, the better the fidelity, but the larger the data file.

Digitizing must produce a set of numbers a computer can read. Computers use binary, a series of ones and zeros, representing the on or off state of a switch. Each digit is called a bit.

Since a switch has two states, binary numbers are based on powers of 2. Each digit represents another power of two. The first ten powers of two equal 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024. (These numbers are also used to measure memory capacity, so some of them will be familiar from the labels on flash drives or other computer media.)

Bit depth is the number of bits that can be used to measure a sample. A bit depth of 3 (2 to the 3rd power, or 2x2x2=8) would only have 8 levels between silence and maximum. This would give very poor fidelity. A bit depth of 10 (2 to the tenth power) would have 1024 levels, and give much better fidelity. Camcorders generally sample sound at 16-bit. The lab's R-09HR recorders can sample at either 16-bit or 24-bit. 16-bit has 64k, or over 64 thousand levels; 24-bit has 16M, or over 16 million levels. Like sampling rate, the larger the bit depth, the better the fidelity, but the larger the data file.

Resampling is the process of changing a digitized sample from one bit depth or sampling rate to another. For example, you might have to resample a CD audio recording from 44.1 kHz to 48 kHz to make it compatible with a video project you are editing. This usually causes a loss of fidelity, so it is important to make the original recording with settings that will not require resampling. Generally, you should record sound at the same settings as the video camera you will be using. 16-bit, 48 kHz is the most common setting at present.

Digitized sound data can be stored in a variety of file formats. WAV is a common audio file format that can be used on both Windows and MacOS platforms. WMA is a Windows format that must be converted before it can be used on MacOS. AIFF is a native MacOS format that can be imported by Audacity on Windows as well. All these formats have the option of being uncompressed, that is, all the original data is intact.

Another common audio file format is MP3, which is a contraction of Moving Picture Experts Group - Level 3, or MPEG-3. This was originally developed to encode sound on DVDs. It is a lossy compression format, which means it throws away part of the sound data so the file size will be smaller. Once a digitized sound is compressed in the MP3 format, the original sound is lost and cannot be reconstructed. If an MP3 file is edited and saved again, it loses even more data to compression, like making a photocopy of a photocopy.

You should always make original recordings in an uncompressed, lossless file format so you can edit them without losing fidelity. Lossy compression formats like MP3 should only be used for distributing your finished work. The lab's R-09HR recorders can record in both WAV and MP3; make sure you set the recorder to WAV for your recordings.

Journalism: Audio from your community

For your audio packages, you will need nat sound – natural sound, the audio environment or background sound that is natural to your community.

Without nat sound, your packages will sound dead and artificial.

Everywhere you go in your community, whether it’s for an interview, an event, background research, or maintaining contacts with your sources, you should record and log clear nat sound elements.

Logging elements means editing, naming, and organizing the digital files so you can find them easily when you are under deadline pressure.

As you build up a nat sound library, you can use those elements to mix into your packages, making them more lively and interesting.

You should also design a sound ID for your packages, an intro, bridge pieces, and exit that you will use consistently to alert your audience that they are about to hear one of your pieces.

Be careful not to use any part of anyone else’s existing sound ID in your own ID.

Audio Basics lecture notes, 9/6/11

deciBel dB unit of measure for sound intensity (Alexander Graham Bell)
inverse square law - the loudness of a sound drops off as the square of the distance from the source. 2x as far = 1/4 the loudness, 1/2 as far = 4x loudness
+6 dB is twice as loud, -6dB is half as loud.
dB is a logarithmic or log scale, NOT a linear scale.
+6 dB is twice as loud, +12 dB is four times as loud, +18 dB is eight times as loud, +24 dB is sixteen times as loud.
Basic Rule: Get your microphone as close to the source as you can.
Signal, Noise
S/N ratio
Signal is the sound you want, noise is everything else.
You want a strong, clear signal, and as little noise as possible. That’s a good signal-to-noise ratio.
Measure the dBs of room tone or ambient sound; that’s noise.
Measure the dBs of the voice or other sound you want the audience to hear; that’s signal.
The difference between the two should be as large as possible. Less than 24 dB is pretty much unusable.
Sound is messy, it bounces around. You can't block sound. There is no such thing as a zoom microphone. A 'directional' mic simply hears a little better in one direction than another.
You need to keep the mic close to the signal source, and far away from noise sources.
The mic on the Flip phone is the little hole beside the lens. You need to get that hole as close to the subject's mouth as possible, it doesn't hear very well.
You have to monitor the sound you are recording through headphones.
If your ears are open to the air, your brain is processing everything you hear and eliminating a lot of the noise. When you listen through headphones, you hear exactly what the microphone and recorder are getting, including all the noise.
If you do not monitor sound, you will get unusable sound - and unusable sound means unusable video.
Supplemental Reading: PGSDV 1 How Sound Works, in Course Materials