2010/06/lumolabs-understanding-image-sharpness.html#comments This White Paper is one in a series of articles discussing various aspects in obtaining sharp photographs such as obtaining sharp focus, avoiding shake and motion blur, possible lens resolution etc. This paper tries to provide a common basis for a quantitative discussion of these aspects. Many authors use some form of test chart which contain high contrast lines with varying distance. Their distance is typically described as ' lines per mm' where mm applies to the recording medium (sensor) rather than the test chart. In the digital age this head led to confusion because some people treated the background color as yet another line. In order to be precise, the test chart line density is now described by ' line pairs per mm' or lp/mm or ' cycles/mm' and means the same as lines per mm. The varying interpretation is now described by ' line widths per mm' or LW/mm.

In order to become independent on the size of the recording medium, all measures are often scaled to the image or picture height (PH).

LW/PH is a popular unit and with a 35mm film or sensor, 100 LW/mm are 24 mm/PH × 100 LW/mm = 2400 LW/PH. LW/PH is often compared directly against the vertical pixel resolution of a sensor and many incorrectly believe that resolution measures cannot get larger than it. Another unit is ' cycles/pixel' which is 0.5 when LW/PH equals the vertical number of pixels.

Zeiss siemens star chart printable