On Sun, Apr 11, 2010 at 06:52:16PM +0200, Toine scripsit: > Yes it does have a filter like element on the mount side. I can't > remove it manually. Tried a UV filter today and my impression is > sharpness has improved, almost razor sharp. Focusing is very > difficult. It pops in and out of focus maybe I need a Katz screen.
Katz screens are helpful, but focusing being difficult is an inherent property of catadioptric designs; the plane of focus is very flat and has no depth to speak of (most but not all of a blackbird (treating North American robins and the Eurasian blackbird as equivalent units of measurement) at 20m, plane-of-focus depth.). This is great for many applications, especially off support, but it's something of a trick for hand-held shooting. I can manage one in five shots having the plane of focus more or less where I want it handheld on a very good day with something to lean against. Some days it is more like one in 15. -- Graydon -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
