I have used a lot of converters over the years, and while the Pentax 1.4 -L en 2x -L are the best optically, there are some others that are quite good too.
The Pentax 1.7 is one of them, but is not very well suited to work with AF lenses, it just uses its own (limited) focussing range and needs some pre-setting of the distance to work well. Of the other brands, the best ones I have used that do AF are the Sigma APO teleconverters. I have the 1.4x EX and 2x EX versions and they remain pretty good contrast and sharpness. There is some light fall-off (vignetting) though when using them with big lenses like the 2.8 300mm, the diameter of the glass is just a little too small for thos big lenses. (the Pentax -L converters are noticably larger) But for use with regular AF lenses I found them very comfortable to use while remaining good enough quality. Results are noticably better than with many el-cheapo converters ... Regards, JvW On Fri, 6 Dec 2002 17:12:34 -0800, Bruce Dayton wrote: > >I don't know that any of them really stand out. They are all designed >about the same and cost about the same. I seem to recall that both >Tamron and Tokina made some more recent Pro grade converters but >didn't make them in Pentax mount. > >Basically, your quality will go down as the power goes up. The 1.4/5 >converters will suffer less optical quality drop than the 2X's. I >personally have a Tamron 2X AF converter and it does in a pinch. ------------------------------------------------------------------ Jan van Wijk; http://www.dfsee.com/gallery
