DIT Flashcards
what is luminance
black and white used as a single brightness signal (luma Y)
Difference between nesting and opening a sequence in a new sequence?
Nesting sequences means using a sequence as a clip within another sequence. You can edit the nest outside of any sequence and the change will be reflected in said sequence. As opposed to a workflow where you only use different sequences and changes wouldn’t be carried over.
what are the 3 encoded signals
- (RGB) or (LUV) -Color Models
(There is some debate over which format is better for frame grabbers: YUV or RGB. … YUV color-spaces are a more efficient coding and reduce the bandwidth more than RGB capture can. Most video cards, therefore, render directly using YUV or luminance/chrominance images.)
4:2:2 explained
luminance represented by 4, each chrominance signal represented by 2 and 2. Uncompressed signal is 4:4:4 color, extremely heavy, high end video routinely throws away 1/2 of color pixels, it is an almost in-discernable difference, the eye is much more sensitive to brightness. Throwing away this color info is called color sampling or color subsampling.
what is chrominance
(chroma or C for short) is the signal used in video systems to convey the color information of the picture
- (separately from the accompanying luma signal (or Y for short). Chrominance is usually represented as two color-difference components: U = B′ − Y′ (blue − luma) and V = R′ − Y′ (red − luma). Each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard.)
what is composite video
when all 3 component signals are joined into 1 composite signal
Difference between interlace scanning & progressive
Progressive transmits frame by frame. Interlace transmits half a frame by half a frame. With interlace only 1/2 a frame is recorded at a time, each frame on screen is composed of 2 frames where every odd pixel line is one, and every even another.
downside of interlace scanning
various artifacts can occur, such as aliasing and twiter
Contrast Defined
can be thought of as a seperation of tones (light anddark)
low contrast images are called ______ or ________
flat or soft
what are compression schemes called
Codec’s
What is the goal of a Codec
To shrink video/audio data down to a smaller size while maintaining quality.
One way to compare video formats
look at how much data they create (data rate)
Video Formats are often measured in _____ ?
Megabites Per Sec. Mbps. uncompressed standard Def. = 172 Mbps compressed DV Format = 36 Mbps
Compression is often indicated as what kind of relationship between it’s source material?
often indicated as a ration between original & compression. ex. DV is 5:1, DigiBeta 2:1, HDV 40:1
significant recent codecs
MPEG-2 makes 40:1 of HDV possible (blu ray, digital tv) MPEG-4 codes like H.264 are widely useed in internet. AVCHD - used in most DSLR’s
Why is the NTSC frame rate 29.97 fps
In the US electric power runs at 60 Hz. Initially permitted 60 interlaced fields (30 FPS) per second. But The color component of the broadcast signal cause’s interference at 60 Frames Per Sec, so a 1% reduction reduces the problem.
NTSC (National Television System Committee) frame rate for 24 FPS is actually
23.976 (23.98) fps
Gamma
Determines apparent contrast (visibility in shadows)
Too high on sharpness causes what? Too low causes what?
high - images are electric low - images are soft
What is a Hue
what we would commonly call the color,
What is Saturation
how much of a given Hue in a filter. Low saturation is closer to white. High Saturation has a lot of one particular Hue.
Chroma effects what? Saturation Effects what
Chroma deals with different aspects of brightness. Saturation is how much of a given Hue might be found, while Chroma deals with where that Hue falls in a spectrum from full gray to full Chroma
High chroma means ___ and low chroma means___
high: bright, deep colors low: pale; desaturated
