Chip Louie wrote: > > Craig Zendel wrote:
> > Anyone know why my 50mm f/1.4 does not record the focusing distance in > > D60. > Could it be due to the fact that the USM motor in the EF 50 1.4USM is not > a ring type USM but a micro-USM and cannot give this type of positional > data? > I was just guessing as to why this seems to not work. The "fact" part was > related to the EF 50 1.4USM having a micro USM AF motor, not a ring type > USM. I'd also venture a guess that most of the older non ring USM lenses > fail to give this information and that even the older ring USM lenses > without internal or rear focusing groups work the same. But I don't know > as I have not been able to use an EOS D60 yet and even if I did have > access to one I don't have any of the older non USM or USM lenses without > IF or RF groups to test it with. I'm sure that someone here will fill us > in as time goes by. > <Clipped> > > My thinking was given that a ring USM is made up of relatively large > circular structure surrounding the focusing group cam tube they would > offer a convenient location to put positional encoders with a very high > level of resolution. A micro-USM motor cannot offer this same large > diameter structure to work from and would offer much less accurate > positional information without a more complex mechanical and electronic > arrangement for a positional encoder. I suppose they could have put them > on the cam tube of the focusing group of the EF 50 1.4USM but this seems > less convenient than simply using a ring USM's structure and electrical > conduits for signal transmission for the encoder. Perhaps this is why Canon does not use distance information for flash exposure calculation. Cheers Keith * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
