Archived posting to the Leica Users Group, 2004/01/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]To amplify what I wrote a little while ago: > Also remember that "sharpness" is not a objective, quantifiable value as are > contrast and resolution. Contrast is objective and scientifically quantifiable. As to resolution, one has to qualify. Unlike contrast, the resolution of a lens does not establish itself scientifically and mechanically and then transfer to a computer for print-out. Whether a resolution value is obtained by photographing a wall chart of smaller and smaller lines or by peering through the ocular of the EROS machine at smaller and smaller lines projected through the lens (which is what we did at Optikos), the determined value depends upon what the observing human eye sees - or thinks it sees - when looking through a loupe at the negative or at the projected image through the EROS ocular. What one sees is to a certain extent subjective because the acuity of the human eye differs from one human to the next. And subjectively, if one wants to think that one can see line separation at a particular set of line fineness that equals 250 lp/mm, perhaps one's brain will say: yes I see the separate lines. Erwin has pointed this out. I did not see it so clearly until this experience looking through the ocular at Optikos. Which is why, when we were determining resolution, Roy Youman and I each wrote down our observations at each f/stop before we knew what the other had "seen." And we then took the lower resolution value. Who has time for this stuff anyway? Seth LaK 9 - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html