It's one thing to test a lens for suitable sharpness and focus accuracy. it's quite another thing to compare two lenses.
To make an accurate comparison, you would have to test several samples of new lenses on a bullet-proof rig. To test two used lenses, one of which once had to be disassembled for fungus removal, is meaningless. Even testing just two new lenses is somewhat suspect, as there is always some sample variation among mass produced products. I It doesn't take much to knock an element out of alignment. I always get a kick out of posts wherein someone relates how they dropped a lens on concrete, then report how it's still okay since only the filter ring is bent:-). Paul On Feb 13, 2011, at 9:54 AM, Luiz Felipe wrote: > Bob, I did my tests with both m50 flavors I have around, matching the > apertures from f11 until both were wide open. I targeted a tiled wall, with > coins taped at center and near corners. Running, between rains. Will repeat > one of these days with care so I can post results. Mirror used to get things > properly aligned, don't believe in great errors. > > Anyway, my 1.4 acted softer than the 1.7 on matching apertures. The 1.4 is > older, had some fungi removed from front and rear elements but there are no > stains in the coating - that may be the problem anyway. But I got the idea > that the 1.7 is a little sharper - at least, mine is. There some diff in > exposure - I was using manual speeds, metered from the Gossen often but not > for every shot. Next time I'll get it proper. > > Luiz Felipe > luiz.felipe at techmit.com.br > http://www.techmit.com.br/luizfelipe > > Bob's words: > It may be just me, but I'd compare the f/1.7 lens with the f/1.4 *AT* f/1.7. > > Reason? If they're both about the same at f/1.7, then the f/1.4 lens is just > as good as the f/1.7 for all purposes you would have used the f/1.7. Bonus: > a little more aperture available to control DOF with the 1.4. > > Bob... > --------------------------------------------------------------------- > I don't mind if you don't like my manners. > I don't like them myself. They're pretty bad. > I grieve over them on long winter evenings. > -- Humphrey Bogart, "The Big Sleep" > > > > -- > 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. -- 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.
