On Sun, 9 Jan 2005 20:05:11 -0500, Herb Chong wrote: >i read about this "slow or useless AF performance in low light" on the *istD >comment and i wonder every time what is really going on. i shoot a lot of >waterfall shots with a 10 stop ND filter mounted. that gives me typically 8 >second exposures at f11 or f13 at ISO 200. i set the camera to point select >AF mode, choose a focus point, press the shutter release half way, it >focuses and lock correctly (usually on the first try), and i take my >picture. the 10 stop filter is mounted while i am doing this. it's almost >impossible to see *anything* in the viewfinder except the readouts, yet the >AF works and i get correctly focused images pretty much all the time.
There are 2 problems with all this discussion. One is that there is no definition of low light, the other is that in truth the problem with the autofocus is with low contrast rather than low light. In day light even with a 10 stop ND filter there is still the inherent contrast in the image to capture focus. In near dark situations the light is generally very diffused which cuts down on contrast and makes it harder for the AF to find something to lock on to. Leon http://www.bluering.org.au http://www.bluering.org.au/leon
