Hi Fred, I have the Sigma 2.8-4.0 and can't say I'd recommend it. I find it quite poor at the wide end and even though it's better at the long end my Tamron 28-105/4-5.6 outperforms it every time. I'd usually rather bump the ISO a notch and use the Tamron. Because the Tamron is more contrasty the autofocus is as good or better even though a stop slower. As Godfrey says the wide open contrast is what really counts in autofocusing. For the type of thing you are describing I have been using the Tamron SP90/2.8, one of my favorites.
Don > -----Original Message----- > From: Fred [mailto:[EMAIL PROTECTED] > Sent: Tuesday, November 29, 2005 8:39 AM > To: pentax-discuss@pdml.net > Subject: Sigma 28-105/2.8-4 > > > Hi, all. > > Does anyone have any opinions on the Sigma 28-105/2.8-4 ? > > I'd like a faster autofocus 28-105 than the Pentax FA 28-105/3.2-4.5 or > either of the FA 28-105/4-5.6's (although the 28-105/3.2-4.5 is marginally > faster than the others). (This would be for use on an *ist DS.) > > However, I'm afraid of: > > 1. softness > > 2. flimsiness > > 3. bad bokeh > > I know very little about Sigma lenses (except for some generalities that > may or may not apply to this particular lens). Any opinions? Thanks. > > [Gee - I really wish that Tamron made the 28-105/2.8 in Pentax mount.] > > Fred > >
