Archived posting to the Leica Users Group, 1998/11/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]All this talk about whether Kodachrome or Fuji Velvia is best and how to evaluate them, especially Erwin's last post with the conclusion "MTF charts are the way", inspired me to grab a couple of data sheets and look at the MTF charts. But I must confess ignorance in not knowing how to interpret the curves. What does the "spatial frequency" on the horizontal axis mean? Is it simply lines per mm? And what is special about the number 20 that Leica lenses are calibrated to? On the vertical axis we have some percentages. For instance, in the curve for Fuji Provia (and Sensia) I see that for a spatial frequency of 20 the corresponding percentage is about 70%. What does this mean? I have some vague idea that a higher % is better, but what does this imply for ordinary usage? And finally, I see that for spatial frequencies lower than 10 the percentage is above 100%. Why? Thanks in advance for enlightening me. Nathan - -- Nathan Wajsman Overijse, Belgium Photography page: http://members.tripod.com/~belgiangator/index.html Motorcycle page: http://www.geocities.com/motorcity/downs/1704/index.html