Le 7.8.2002 19:48, « Brian Blankenship » <brian@bngraphics.com> a écrit : > > Does anyone know if the rule/law holds true for prime lenses as well? The rule is true for all lenses with some nuances and these nuances makes all the differences between good/expansive lenses and cheap ones. Greg explained the rules : at the wider apertures there are one kind of aberrations and at the smaller apertures other kinds; the best apertures occurs where you are able to minimize both kinds of aberration and where it happens exactly depends upon the lenses construction, but affects both prime lenses and zooms : the difference is the level of sharpness you are getting and the flexibility offered by good prime lenses in matters of film choices and shutterspeed/aperture choices. Zeiss and Leica glass are so well renowned and expansive because they are able to offer very sharp pictures at very wide apertures, but in their case too, there is an optimized aperture which is neither the largest, nor the smallest. For instance a lense may be good at F2, F2.8 and excellent from F4 to F8 or F11, then good again from F16 to F22 (that could be a Zeiss lense) While a cheaper lens will be satisfying from F2.8 to F5.6 and good at F8-F11, satisfying at the smaller apertures. You can read about these tests in many photoamateur magazines and it is always interesting to know where your lenses are strong or weak.. -- Christiane
