X
X-ray. Very short wavelength electromagnetic radiations. Very penetrating and used for
photgraphing skeletal structures of people.Y
Y/C. A video format found in Super-VHS video recorders. Luminance is marked with
Y and is produced separate to the C, which stands for chrominance. Thus, an S-VHS
output Y/C requires two equal length coaxial cables for a perfect output.
Y, R-Y, B-Y. The general set of colour difference signals used in the PAL system as well as
for some encoder and most decoder applications in NTSC systems; Y is the luminance
signal, R-Y is the first color difference signal and B-Y is the second color difference signal,
also known as YUV.
Y, U, V. Luminance and color difference components for PAL systems; Y, B-Y, R-Y with
new names; the derivation from RGB is identical.

Z
Z. In electronics and television this is usually an abbreviation for impedance.
Zoom lens. A camera lens that can vary the focal length while keeping the object in focus,
giving an impression of coming closer to or going away from an object. It is usually
controlled by a keyboard with buttons that are marked zoom-in and zoom-out. The change
in focal length of the lens does not result in a physical length of the lens.
Zoom ratio. A mathematical expression of the two extremes of focal length available on a
particular zoom lens.