Archived posting to the Leica Users Group, 2003/07/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]John, AF to some extant depends on some purely mechanical settings that can cause misfocus. We all know that an SLR depends on the distance to the film plane be matched to the distance to the ground glass screen by way of a mirror. However, the AF mechanism depends on a sub-mirror that bounces the light onto the AF sensors. Very small movements (temperature expansion for example) can affect the accuracy of the auto focus. A real world example would be a SLR that has received hard use occasionally needs the mirror reset to the proper angle. In the old days there was a fixed stud that caught the mirror at the correct position. Not discussed here, but the budget SLR's especially have pretty wide tolerances for auto focus as the AF sensor is in plastic which does move enough. But hey, nobody uses an 85 F1.2 on such a body. 0.02 Don dorysrus@mindspring.com On Monday, July 21, 2003, at 03:31 PM, George Lottermoser wrote: John wrote in part: - - For poorly lit or low contrast subjects on medium lenses, the RF wins for me. - - For poorly lit subjects at close distance, the AF is generally more accurate unless you have really calibrated your RF as described above. - - For lenses 75mm and greater, especially wide open or in poor light, AF is better than RF but MF on an SLR is better than both of them. Those are my personal prejudices. The probably don't reflect anyone else's experience. - -- John Brownlow http://www.pinkheadedbug.com http://www.unintended-consequences.com - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html