rtvf lecture 2
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primary factor in determining the quality and cost of a camera (followed by lens). light turns into electricity through transduction.
how clear a picture is or how much fine detail can be "resolved" (seen) by a camera; how many lines a video picture has. quantitative or qualitative
lines refer to scan lines. number of scan lines is fixed on scanning system used. SD video has used 480 horizontal scan lines per frame of video (vertical resolution of 480) multiple number by 1.33 (4:3 ratio) and horizontal resolution is 640, HD uses 720 or 180 multiplied by 1.77 (16:9)
lines refers to picture lines, number of picture lines that won't mess together when shooting a resolution chart. depends on quality of imaging element. point camera at resolution chart and see what picture detail is visible on a monitor, SD has at least 700-800 picture lines, HD exceeds 2000 picture lines
resolution-marked with parallel and converging lines. grey scale/chip marked with black and white chips, chart should be used to white balance. dumonde is chart with color and skin tone.
Charged Coupled Device
first solid state imaging element utilizes chip technology (analog), consumer CCDs are 1/6", 1/5", 1/4" or 1/3", professional CCDs are 2/3" square. larger ones can have shallow DOFs, small ones everything's in focus
CCD cameras will employ anywhere from
one to three chips. consumer quality only uses 1 chip with R, G and B sensitive areas. industrial quality (like Panny 80s) use 1 chip. broadcast quality always uses 3 (2/3") chips.
how CCDs work
array or grid of picture elements (pixels) is charged based on amount of light striking the chip. more pixels=better image. 1-2 megapixels in 2/3" CCD cameras
how CCDs work. as like strikes,
the pattern of charges is transferred pixel by pixel "bucket brigade" style from input to the storage register, where the charges are then transferred to the output register where an electrical signal is now formed. charges are transferred directly and completely so no image retention occurs and the input chips is totally blank again.
CCDs have an electronic
shutter to help regulate blanking process to provide image sharpness during fast motion. allows blur-free slow motion and freeze-frame recording but shutters require brighter images or cause a loss in DOF. used to be mechanical.
advantages of CCDs over old imaging element, the pickup tube 1-3
1. better in low light situations (more sensitive to it) 2. no tube like image retention (comet tailing or burn in) 3. no tube like registration errors CCDs only have to be physically registered once at the factory (when the chip is cemented to the prism block)
advantages of CCDs over old imaging element, the pickup tube 4-8
4. drastically reduce power consumption 5. drastically reduce camera size/weight 6. last forever 7. cheaper upkeep over time 8. higher resolution due to higher pixel counts and micro-lens technology.
highest end digital cameras
used for digital cinematography, taking CCD chips to new levels of resolution, "Red One", use larger sensors 4/3" or 35mm, only single sensor to allow film lenses to be used
disadvantages of CCDs
1. sometimes there's a form of visual distortion "vertical smear," the more expensive "FIT" chips get rid of this problem 2. fixed pattern noise-when shooting certain images with complex, closely interwoven patterns, moire effect
history of CCDs
used for broadcast in 1984 at political conventions, popularized by NBC, when they go bad you can't swap chips you have to send it back to the maker for replacement
Complementary Metal Oxide Semiconductors
newest, increasingly popular solid state imaging elements, similar to CCDs but with one technical difference
advantages of CMOSs over CCDs
1. simplified circuitry within camera leads to further reductions in cost 2. ability to have higher frame rates (up to 150 fps) 3. cheaper to make 4. higher dynamic range 5. better color fidelity 6. use even less power
Disadvantages of CMOSs compared to CCDs
1. increased fixed pattern noise 2. less sensitive to light 3. skew and wobble when panning
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