Archived posting to the Leica Users Group, 2001/02/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Austin Franklin wrote: >Martin, as both Jim and I have pointed out, the film size is completely >irrelevant, and so is completely covering the film format. It is not an >assumption, it is a fact. You are confusing optical DOF with printed DOF. Austin, Plane of focus is real. DOF is not real. The concept of DOF is based on an "acceptable circle of confusion" at various distances from the plane of focus. DOF is a generally agreed upon area around the plane of focus that produces an acceptable result to human eyes. There is no absolute DOF, it is an agreed upon value that most think gives a "good enough" result. As lenses and film have improved the generally accepted DOF may not be sufficient to describe the phenomena with great accuracy. But that's another issue. It may be that a definition or way of thinking that works for you is different from what works for others. But when you choose to operate outside of the accepted values you are on your own. Doing so and expecting others to buy into your new version of DOF is extraordinary. Read this: http://Fox.nstn.ca:80/~hmmerk/DOFR.html which in part states: "The starting point of the existing theory was that there is a limit on the resolving power of films and lenses. That limit was said to yield a smallest spot having a diameter equal to one-fifteen-hundredth of a normal lens's focal length. Thus the maximum permissible "circle of confusion" is 1/30 mm in diameter for a 35 mm camera with its 50 mm standard lens." and lots more at: http://Fox.nstn.ca:80/~hmmerk/HMbook14.html Again, your ideas of "optical DOF" and "printed DOF" are your own. They are not part of any accepted explanation of the phenomena of our seeing something as in focus when it in fact is not. I think you have re-invented the wheel. And your wheel is not particularly round. Henry Ambrose