Archived posting to the Leica Users Group, 2000/11/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>>>>> What you call film-plane DOF is not soley determined by subject distance, focal length, and aperture. It is also determined (and this is *critical*) by the size of the CoCs that you are willing to accept. I believe that in 35mm photography, a standard circle-of-confusion size is 0.03mm. If you plug a different CoC size into the equations, the DOF will change even leaving the subject distance, focal length, and aperture the same. Once you stop thinking of DOF as an objective property and start thinking of it as "the zone of perceived sharpness around the focus plane", you realize that DOF "around" the subject, on the negative, and in the print are all just different ways of looking at the same thing. It is just a convenient, standardized representation of the limits of visual perception as it pertains to photography, and not conceptually different entities. Outside the equations, in the "real" world, DOF doesn't exist. <<<<< Well, I got all of that Martin. After all, even the definition of focus is going to change from lens to lens. I wasn't thinking of it as an inherent property of the lens but as determined by those factors when the CoC thing had been set. But I didn't say it! Incidentally, I believe Zeiss uses a factor of 0.02mm for their depth of field markings, is that right? I read it somewhere, maybe on Erwin's site. But since I don't have any Zeiss lenses I can't compare their markings to the Leica ones. Still this discussion did clear something up for me, which is now making MF look much more attractive! "Outside the equations, in the real world..." - Martin, you know better than that! As to the 4mm spacer, I don't think there'd be much profit margin in something like that. It wasn't cheap for me! Tom A would be the best person to do it, I suppose, since he's already tooled up. As I said I find it a very real improvement on the existing shutter dial. And it doesn't interfere with the Voigtlander or Leica accessory finders. You lose the flat-topped Leica look, though. The battery cover - well, I already had the knurled cover on my cameras but they seemed to lock up so this was a solution. One of the original covers is now missing its leatherette because that came away while I was trying to unscrew the damn thing. Rob. Robert Appleby V. Bellentani 36 41100 MO Italy tel. (+39) 059 303436 mob. (+39) 0348 336 7990