Good vs. Bad UV Haze filters?
in [Digital Cameras]
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From: jean-daniel dodin on 7 Jan 2010 13:03 Le 07/01/2010 18:45, Neil Harrington a �crit : > Not in my personal experience, but I have read that even a fairly deep > scratch is unlikely to make any visible difference in imaging. urban legend... may be related to the focal length. put a hair on the lens of a smartphone, you can see it (or it's shadow). Try the same on a better lens with different aperture. after all, experimenting is easy with digital cameras jdd -- http://www.dodin.net Le wiki des forums son-image fran�ais: http://new.dodin.org/frsv/ http://valerie.dodin.org
From: David Ruether on 7 Jan 2010 14:17 "jean-daniel dodin" <jdd(a)dodin.org> wrote in message news:4b4621d7$0$29883$426a74cc(a)news.free.fr... > Le 07/01/2010 18:45, Neil Harrington a �crit : >> Not in my personal experience, but I have read that even a fairly deep >> scratch is unlikely to make any visible difference in imaging. > urban legend... may be related to the focal length. Yes. A relatively long focal length lens with a relatively large sensor area would probably show little or no ill effect from a fairly deep scratch even at a smallish stop with textured subject material - but with a good WA converter on a good 1/3rd" CCD video camera set at WA, even the tiniest, barely visible pin-prick sized "tick" in the front element glass can show in side and back lighting conditions. > put a hair on the lens of a smartphone, you can see it (or it's > shadow). Try the same on a better lens with different aperture. after > all, experimenting is easy with digital cameras > > jdd Yes - this is one of the downsides of compact cameras. Even a friend's Panasonic FZ35 had spoiled pictures likely resulting from "spit marks" or condensation on the front element that were difficult to see. --DR
From: Paul Ciszek on 7 Jan 2010 14:46 In article <4b45577f$0$1663$742ec2ed(a)news.sonic.net>, Ray Fischer <rfischer(a)sonic.net> wrote: >Neil Harrington <never(a)home.com> wrote: >>In well over 50 years of amateur photography I have NEVER used a filter "to >>protect the lens," though I have used them for their design purpose, >>filtering. I've never yet had a lens damaged by lacking a "filter for >>protection." > >Bully for you. One trip to the beach on a windy day was enough to >convince me that filters are very useful protection. > >Unless you _like_ the front of your lens coated with salt spray? Even before this discussion, I was playing with the follwoing idea: If you placed a sapphire (Al2O3) window between your lenses and the cruel world, and coated the *inside* of the window with a MgF coating, you would have an outside surface harder than anything except diamond, that would be very difficult to scratch and easy to clean, and an inner surface with near-perfect anti-reflection. You would lose 6% of your light from reflection off of the outside surface, though. -- Please reply to: | "Any sufficiently advanced incompetence is pciszek at panix dot com | indistinguishable from malice." Autoreply is disabled |
From: Chris Malcolm on 7 Jan 2010 18:10 jean-daniel dodin <jdd(a)dodin.org> wrote: > Le 07/01/2010 18:45, Neil Harrington a ?crit : >> Not in my personal experience, but I have read that even a fairly deep >> scratch is unlikely to make any visible difference in imaging. > urban legend... may be related to the focal length. > put a hair on the lens of a smartphone, you can see it (or it's > shadow). Try the same on a better lens with different aperture. after > all, experimenting is easy with digital cameras It's not urban legend, and it's got nothing to do with "better". It's the simple basic optics of aperture physical size and depth of field. At f/2.8 at 50mm on a APS-C sized sensor I can photograph through thick wire netting which becomes completely invisible if it's less than about two inches from the lens. It so happens that to get a lens and image sensor of that size you probably have to buy a better camera, but the quality has nothing to do with the swallowing of obstructions close to the lens in depth of field. That's just the basic optics, and would work with a really cheap crappy film camera of the same dimensions. -- Chris Malcolm
From: melanie jones on 7 Jan 2010 18:32
"Ofnuts" <o.f.n.u.t.s(a)la.poste.net> wrote in message news:4b43a2e4$0$21973$426a74cc(a)news.free.fr... > Consider: naked lens falls on wood table corner: heavy and thick lens > harder than wood, no damage to lens. Lens with filter falls on wood table > corner: light and thin filter breaks to pieces, shards make scratches on > the lens. Hood is better. > > -- > Bertrand I agree and disagree. Last year I dropped a lens with a filter, the filter broke and hundreds of particals of glass stuck to the lens. Some of the small particles of glass seemed to be invisible, and over a few months they would reappear all over the lens, beneath my replacement uv filter. In the end I scratched the lens itself whilst trying to clean up residual glass particals. However, this evening I disovered some totally uncleanable smudges on another uv filter. It was just impossible to clean with a cloth or a lens cleaning solution. Out if desperation I dipped it in acetone for 10 seconds and to my amazement the lens did not dissolve and the dirt came off. On this occasion I was glad that I had the filter on the lens. |