Archived posting to the Leica Users Group, 2000/04/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>-----Original Message----- >From: Michel LE [mailto:le@ilog.fr] > >I've noticed that the minimum focussing distance for >rangefinders (Hexar, >Leica or Bessa) is around 70cm, for a 35mm lens, while on >SLRs it is in >the range of 30cmm or 40cm. > >Is this limitation induced by parallax error involved with rangefinder >mechanism or is there any optical justification for this ? AFAIK it's mainly a parallax issue. Nothing would prevent designers from increasing the length of the helicoid, but the parallax would make framing pretty hit-or-miss at 30cm. It also gets harder to focus precisely, due to the trigonometry of the system - there's a much better chance the system isn't focussing where you think it is. The subject can easily fall outside the depth of field, which at close distances in narrow to begin with - so the proportion of out-of-focus images will skyrocket. Paul Chefurka