On 3 Nov 2013, at 03:39, John Francis <jo...@panix.com> wrote: > >> On Sat, Nov 02, 2013 at 10:44:06PM +0000, Steve Cottrell wrote: >> Just on he subject of cleaning lenses - I keep a clean handkerchief in >> one back pocket. Stout blow of hot breath on the element and a good wipe >> round with the hanky and hey presto. I do that with my A*85/1.4 (500 >> quid) and my Canon TV motorized zoom lens lens (5000 quid) and never had >> a problem. These lenses are a lot tougher than people think. > > I've heard stories of someone who used to demonstrate the toughness of > SMC coatings by stubbing out a cigarette on the front element of a lens. >
That's a marketing gimmick, with nothing to do with real world use. The temperature tests the coatings, but in itself is probably not enough to test any glass, which depends on very high temperatures in its manufacture. The ash, paper and tobacco are not going to do any more harm than a wet lettuce. They should drop the lens from head height onto a rock or a pavement, or shoot road grit at it at the speed it flies up from beneath the wheels of a car. If it came away from that unscathed I might allow myself to be impressed. The link someone else posted showing a lens that had been scratched by a filter is probably, paradoxically, a good argument in favour of filters. - as long as you get one that fits the lens properly! B -- 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.
