Are the existing standards and tables to calculate DOF correct for current equipment (considered the technology advance through out the years)? Harold M. Merklinger says "No". He says that "... one could expect to achieve about seven times the resolution usually assumed in that wisdom (current approach to calculate DOF)".
"According to the theories of geometrical optics, a lens focused at distance ‘X’ will require that, for maximum sharpness, the subject be positioned exactly at distance ‘X’. In practice, it is found that if the subject is a little closer or a little farther away, even the best scientific instrumentation will not be able to detect the difference in sharpness. So, in practice, there is a zone within which any subject will be imaged “sharply”, or with acceptable sharpness. That zone of lens-to-subject distances is the depthof-field." - That was the excerpt from Harold M. Merklinger's article called "Adjusting Depth-Of-Field". This article was posted in Shutterbug magazine through several issues (there are four parts). At his website Harold keeps this article for people to read (which I strongly recommend). Here are the links to it: Part I, Part II, Part III and Part IV. There is one more web page that compliments this article, it is called "Depth of Field Revisited", which you probably would want to read as well.