Acutance

In photography, the term "acutance" describes a subjective perception of sharpness that is related to the edge contrast of an image. Acutance is related to the amplitude of the derivative of brightness with respect to space. Due to the nature of the human visual system, an image with higher acutance appears sharper even though an increase in acutance does not increase real resolution.

Historically, acutance was enhanced chemically during development of a negative (High Acutance Developers), or by optical means in printing (Unsharp Masking). In digital photography, onboard camera software and image postprocessing tools such as Photoshop or GIMP offer various sharpening facilities, the most widely used of which is known as "unsharp mask" because the algorithm is derived from the eponymous analog processing method.

In the example image, two light gray lines were drawn on a gray background. As the transition is instantaneous, the line is as sharp as can be represented at this resolution. Acutance in the left line was artificially increased by adding a one-pixel-wide darker border on the outside of the line and a one-pixel-wide brighter border on the inside of the line. The actual sharpness of the image is unchanged, but the apparent sharpness is increased because of the greater acutance.

Sharpness

Coordinates: 51°43′23″N 2°28′41″W / 51.723°N 2.478°W / 51.723; -2.478

Sharpness (/ʃɑːrpˈnɛs/ sharp-NESS) is an English port in Gloucestershire, one of the most inland in Britain, and eighth largest in the South West. It is on the River Severn at grid reference SO669027, at a point where the tidal range, though less than at Avonmouth downstream (14 metres (46 ft) typical spring tide), is still large (10 metres (33 ft) typical spring).

Just to the south lies Berkeley.

Docks

Sharpness docks began as a basin giving access to the Gloucester and Sharpness Canal. There were no port facilities at Sharpness itself and all traffic proceeded up the canal to Gloucester. The original Old Dock opened, with the canal, in 1827. The dock was separated from the Severn by a lock gate. The level of the basin varied for the hour or two for which the gate was open and so it was isolated from the canal by a lock with two gates. This lock was improved over time, expanding to be a ship lock of 163ft length and 38ft breadth and a smaller lock for trows of 81ft and 19ft. An intermediate lock gate was also provided in the larger lock, allowing shorter vessels to pass through more quickly and with less water consumption. A house for the Harbour Master was provided on the seaward dockside alongside the river gate. Today the Severn Area Rescue Association maintain a rescue station in the old house.

Sharpness (disambiguation)

Sharpness is port in Gloucestershire, England.

Sharpness may also refer to:

See also