Archived posting to the Leica Users Group, 1998/01/23
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>The question goes back to Leica design. Do they design for high resoultion? >Do they design for high contrast? Micro details seems to simply be a >description of high resolution and contrast. Am I incorrect about this? Does >micro resolution mean something else? > >Tom Shea I assume that micro resolution means the resolution of microscopic details. You can have good contrast at fairly high spatial frequencies (about 50 lp/mm: to be clear: a linepair is one blackbar and one adjacent white bar). High resolution has no clear meaning: in wafer optics 5000 lp/mm are high resolution, in photography 100lp/mm are counted as high res. The posting giving figures of 400lp/mm for a Leica lens must be surely have been misread or misquoted. Leica lenses are designed for high contrast AND high resolution to the limits of usable visual information. It is impossible to have a lens with 200lp/mm and good contrast. A lens with very high resolving power beyond the limits of film resolution and the capabilities of the eye has worse quality than a lens with a somewhat lower resolution. Leica lenses therefor have a fairly sharp cutoff spatialfrequency, implying that is much better to have NO resolution beyond this cutoff point than to have some resolution beyond this point as this resolution will degrade the contrast and therefore the imag qualities as a whole. As modern optical thinking has it nowadays, a very high resolution figure means automatically a design that is not optimized for optimum photographic quality as it is interpreted these days. The classical statement that Leica goes for smooth gradation and Japanese lenses go for contrast has never been true in the past and is not true now. To bring some perspective: most Leica lenses used by almost all people are being used in circomstances where 20 lp/mm are a very high target. So let us for once forget about resolution figures because maximum resolution is not the qualifier we need to discuss image quality and optical performance. Erwin