In practice, it is difficult to achieve the full dynamic range seen by human beings using electronic equipment, since most electronic reproduction equipment is essentially linear rather than logarithmic like human perception. Electronically reproduced audio and video often uses some trickery to fit original material with a wide dynamic range into a narrower recorded dynamic range that can more easily be reproduced: this is dynamic compression. For example, a good quality LCD display has a dynamic range of around 1,000, or 30 dB (commercially the dynamic range is often called the "contrast ratio" meaning the full on/full off contrast ratio), and some of the latest CMOS image sensors now have dynamic ranges of 110dB, compressing the range into a range, near 30dB, that the human eye may understand. When showing a movie or a game such a display is able to show both shadowy nighttime scenes and bright outdoor sunlit scenes, but in fact the level of light coming from the display is much the same for both types of scene (perhaps different by a factor of 10). Knowing that the display does not have a huge dynamic range, the program makers do not attempt to make the nighttime scenes millions of times less bright than the daytime scenes, but instead use other cues to suggest night or day. A nighttime scene will usually contain duller colours and will often be lit with blue lighting, which reflects the way that the human eye sees colours at low light levels.
Dynamic range of an audio device is also sometimes referred to as the dynamic window. The dynamic range is defined as the difference between the minimum and maximum amplitude a given device can record. For example, if the ceiling of a device is 10 dBV and the noise floor is 3 dBV then the dynamic range is 4.85 dBV.
In digital audio systems the dynamic range is limited by quantization error. The maximum achievable dynamic range for a digital audio system is:
In the analog domain multiple noise processes determine the noise floor of a system and its corresponding dynamic range. Magnetic tape has a dynamic range of approximately 55dB. A vinyl disk has a dynamic range of approximately 65dB.
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. This avoids questionable measurements based on the use of blank media, or muting circuits.
Metrology systems and devices may use several basic methods to increase their basic dynamic range. These methods include averaging and other forms of filtering, 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.
During the film era of photography, Galen Rowell created a filter to increase apparent dynamic range. It consisted of a graduated gradient, neutral density filter positioned in front of the lens at the time the exposure was made. The top half was dark and the bottom half was clear. The dark area was placed over the scenes' high intensity region; usually the sky. The result was more evenly exposed film with increased detail in the shadows and low light areas. Though this didn't increase the fixed dynamic range available at the surface of the film's emulsion, it stretched usable dynamic range in practice. When digital photography became popular, Eugene F. Lally conceived an algorithm that mapped the image and adjusted the signal gain of the pixels in shadows and in highlights to better distribute the lighting range across the image. This technique eventually was adopted by Nikon and called D-Lighting. The technique became the standard in digital cameras and image editing software to expand dynamic range. Eugene F. Lally took the technique the next step into high-dynamic-range imaging (HDR). It represented a new and radical departure from traditional forms of photography. It solved the fundamental challenge of making photographs fit the dynamic range of how we see in real life into the dynamic range available in digital imaging sensors. This technique can be applied directly to in-camera processing and into image editing software. Finally the dynamic range we are capable of "seeing" with our eye/brain processing can be replicated in photography.
"High Dynamic Range Image Sensing Device and Image Sensing Method and Manufacturing Method Thereof" in Patent Application Approval Process
Jun 13, 2013; By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventors LIU, Chih-Min (Tainan...