Hi Graham: Nice to hear from you!
I have a similar Sigma lens, the 18-35 ASP, and while I have not noticed anything in the viewfinder, I have had some recent shots where the focus was just a little off. These were all shots taken in low light, using the RTF, and with no other focussing aid than the AF system. I wondered whether it was down to low-contrast making it harder for the camera to auto-focus, or whether, because I was shooting towrds the wide end of the lens, some other factor was coming into play, such as a mass of fine detail and no large tonal differences? I was using either the MZ-5 or the MZ-S, and I noticed more hunting than usual with this lens and the 28-105 in similar low-light situations. John Coyle Brisbane, Australia On Tuesday, March 05, 2002 10:49 PM, Graham Lyth [SMTP:[EMAIL PROTECTED]] wrote: > Hi all, > > Been lurking here for a while, nice to post for a change. > > This morning, I've been out in the back garden taking some test shots with a > new Sigma 15-30 f/3.5-4.5 EX fitted to my Z-1, and I've come across some > interesting AF behaviour that I've not noticed before. > > Testing at 15mm, I noticed that the AF wasn't focusing precisely on the > subject - it was focusing a few feet in front. I played for a few minutes, > with the camera on a tripod pointing towards the house about 12 feet away, > and concluded that the position of focus varied with the aperture set. Wide > open, the focus was accurate. As I stopped down, the point of focus moved > towards the camera. Presumably, the camera was making a judgement on where > to focus in order to maximise depth of field whilst keeping the subject > sharp. > > I got the same result regardless of whether I changed the aperture via the > ring or the body. The Z-1 is set to use the standard program line, not the > DOF variant. > > I've not noticed this before and haven't seen it discussed - can anybody > shed any light? > > > Graham > -- - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
