![]() - Kelly Abernathy ![]() Contact Kelly Abernathy Kelly Abernathy's Gallery |
Polarizer Problem
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- Kelly Abernathy![]() Contact Kelly Abernathy Kelly Abernathy's Gallery |
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Jon Close |
(a) I don't beleive that the 80-400 VR is par-focal (retains focus when zoomed). You have to zoom first, then focus. (b) AF will become iffy in lower light levels. While the f/5.6 maximum aperture at the 400 setting is nominally wide enough to enable autofocus, when you use the polarizer you lose about 2 stops of light. (c) You are using a circular polarizer, right? If by chance it is a linear polarizer, then it will confound the AF system.
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Anne House |
"when you use the polarizer you lose about 2 stops of light" Jon, Does this mean you could use a circular polarizing filter interchangeably(instead of) with a nuetral density filter? Just curious. Thanks.
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- Kelly Abernathy![]() Contact Kelly Abernathy Kelly Abernathy's Gallery |
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Jon Close |
Dunno. Looking again at the first shot posted, I wonder if the blur is not that the shot isn't focused, but maybe camera shake? Any chance the VR was inadvertently switched off?
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- Kelly Abernathy![]() Contact Kelly Abernathy Kelly Abernathy's Gallery |
Nope - it was on. And I could see through the viewfinder that the shot wasn't focusing. Any idea where I might start some research? Thanks -K
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Steven Chaitoff |
Anne, the two filters aren't interchangeable. They do different things so you shouldn't use a PL filter where you need an ND one. It's like wearing socks on your hands if you don't have any mittens. It'll get the job done, but that's not what it is made for. Keep in mind a PL filter has tiny grooves that only go in one direction. So if you turn it, the reduction in light will vary, typically between 1.5 to 2.5 stops. Plus, common ND filters will reduce light evenly 2, 4 or even 8 stops or more, which is much more than a polarizing filter will do. Also, the main point of a PL is to reduce glare & reflections, which an ND filter won't do.
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Anne House |
Thanks, I appreciate the response. I knew it was too good to hope, hehehe.
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