Dynamic range (abbreviated DR, DNR,[1] or DYR[2]) is the ratio between the largest and smallest measurable values of a specific quantity.
The human eye takes time to adjust to different light levels, and its dynamic range in a given scene is actually quite limited due to optical glare.
The instantaneous dynamic range of human audio perception is similarly subject to masking so that, for example, a whisper cannot be heard in loud surroundings.
A human is capable of hearing (and usefully discerning) anything from a quiet murmur in a soundproofed room to the loudest heavy metal concert.
In practice, it is difficult for humans to achieve the full dynamic experience using electronic equipment.
For example, a good quality liquid-crystal display (LCD) has a dynamic range limited to around 1000:1,[b] and some of the latest CMOS image sensors now[when?]
[16] A professional video camera such as the Sony Digital Betacam achieves a dynamic range of greater than 90 dB in audio recording.
[17] Audio engineers use dynamic range to describe the ratio of the amplitude of the loudest possible undistorted signal to the noise floor, say of a microphone or loudspeaker.
Dynamic range in analog audio is the difference between low-level thermal noise in the electronic circuitry and high-level signal saturation resulting in increased distortion and, if pushed higher, clipping.
Specialized bias and record head improvements by Nakamichi and Tandberg combined with Dolby C noise reduction yielded 72 dB dynamic range for the cassette.
[28]: 75 In 1981, researchers at Ampex determined that a dynamic range of 118 dB on a dithered digital audio stream was necessary for subjective noise-free playback of music in quiet listening environments.
[30] Since the early 1990s, it has been recommended by several authorities, including the Audio Engineering Society, that measurements of dynamic range be made with an audio signal present, which is then filtered out in the noise floor measurement used in determining dynamic range.
The term dynamic range may be confusing in audio production because it has two conflicting definitions, particularly in the understanding of the loudness war phenomenon.
The other end of the dynamic range of measurement is often limited by one or more sources of random noise or uncertainty in signal levels that may be described as defining the sensitivity of the sensor or metrology device.
These methods include averaging and other forms of filtering, correction of receivers characteristics,[43] repetition of measurements, nonlinear transformations to avoid saturation, etc.
In more advance forms of metrology, such as multiwavelength digital holography, interferometry measurements made at different scales (different wavelengths) can be combined to retain the same low-end resolution while extending the upper end of the dynamic range of measurement by orders of magnitude.
[57] The most severe dynamic-range limitation in photography may not involve encoding, but rather reproduction to, say, a paper print or computer screen.
In that case, not only local tone mapping but also dynamic range adjustment can be effective in revealing detail throughout light and dark areas: The principle is the same as that of dodging and burning (using different lengths of exposures in different areas when making a photographic print) in the chemical darkroom.
The principle is also similar to gain riding or automatic level control in audio work, which serves to keep a signal audible in a noisy listening environment and to avoid peak levels that overload the reproducing equipment, or which are unnaturally or uncomfortably loud.