The term sharpness is used in acoustics, photography, image processing and as image sharpness also in the display of images and photos.
- Inacoustics, sharpness is a psychoacoustic phenomenon produced by high- frequency sound signals and is largely independent of level. Acum has been defined as the unit of sharpness; where 1 acum corresponds to the perception of sharpness produced by the noise of a bandpass filter of 1 kHz with a bandwidth of 200 Hz at a sound pressure of 60 dB. The Asper value for roughness is noticeable in hiss.
- Inphotography, sharpness is understood to be the subject projected onto the light-sensitive image sensor at the highest resolution. The highest sharpness is set by the adjustable distance between the lens system of the lens and the image sensor, the range of sharpness by the f-number. The higher the f-number, the smaller the lens opening and the greater the depth of field, also called the depth of field.
- In image processing, sharpness is a characteristic value for graphic representations, which is reflected in the contour of objects and abrupt transitions. Graphics programs offer corresponding functions to influence sharpness during image processing. With these techniques, the differences in brightness between objects are intensified, emphasizing the contours and edges.
- Image sharpness is also used in image reproduction. This refers to the resolution of the finest image details. This image sharpness is specified in the number of lines per millimeter, lines per inch( lpi) or as a bandwidth value in megahertz( MHz). A high image sharpness is given when a pixel does not fall below one thousandth of the image height.