The frequency modulation of the VHS luminance signal is limited to 3 megahertz, which makes higher resolutions technically impossible even with the highest-quality recording heads and tape materials, but an HQ branded deck includes luminance noise reduction, chroma noise reduction, white clip extension, and improved sharpness circuitry.
32.
These signals could then be broadcast separately on a different frequency; a monochrome set would tune in only the luminance signal on the VHF band, while color televisions would tune in both the luminance and chrominance on two different frequencies, and apply the reverse transforms to retrieve the original RGB signal.
33.
Compared with component video, which carries the identical luminance signal but separates the color-difference signals into Cb / Pb and Cr / Pr, the color resolution of S-Video is limited by the modulation on a subcarrier frequency of 3.57 to 4.43 megahertz, depending on the standard.
34.
Early colour television studio cameras consisted of four tubes to relay the picture : three were receptive to colour ( red, green and blue the chrominance signal ) with the fourth providing a high-resolution monochrome image ( the luminance signal ) which was still required as many viewers still watched on monochrome receivers.
35.
In the case of a four-tube camera, there is a problem with colorimetry if the signal from the luminance tube is used in unmodified form to represent Y, because that signal is likely to be panchromatic, rather than having a characteristic similar to the luminance signal given by the equation above.
36.
When analog television was developed, no affordable technology for storing any video signals existed; the luminance signal has to be generated and transmitted at the same time at which it is displayed on the CRT . It is therefore essential to keep the raster scanning in the camera ( or other device for producing the signal ) in exact synchronization with the scanning in the television.
37.
In this equation a _ 1 and a _ 2 are attenuation factors, E _ y is the luminance signal, ( E _ b-E _ y ) and ( E _ r-E _ y ) are the so-called color difference signals and \ omega is the angular frequency of the color carrier . \ omega is within the luminance bandwidth.
38.
To provide sufficient bandwidth for the chrominance signal, yet interfere only with the highest-frequency ( and thus least perceptible ) portions of the luminance signal, a chrominance subcarrier near 3.6 MHz was desirable . 227.5 = 455 / 2 times the line rate was close to the right number, and 455's small factors ( 5 ?7 ?13 ) make a divider easy to construct.
39.
In the ideal case, a camera might measure luminance directly and store this in the HDR image; however, most high dynamic range images produced by cameras today are not calibrated or even proportional to luminance, due to practical reasons such as cost and time required to measure accurate luminance values & mdash; it is often sufficient for artists to use multiple exposures to gain an " HDR image " which grossly approximates the true luminance signal.
40.
And the processing in a colour receiver assumes that the luminance signal has this form, when the decoding of the composite signal into the individual colour components takes place . ( The spectral senitivity of the red green and blue channels had pre-defined characteristics which were achieved, in practice, by a combination of ( a ) the characteristics of dichroic reflection surfaces, ( b ) optical filters ahead of the pick-up tubes and ( c ) the spectral characteristics of the pick-up tubes ).
