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02-20-2014, 04:27 PM   #1
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Filter size

does anyone knows if filter is special or is normal. Cuz i read on a page that filter is non-rotating for this lens, is this true or not
http://www.photozone.de/pentax/129-pentax-smc-d-fa-100mm-f28-macro-review--test-report

Can i use a std 49mm fitler or must be non rotating?

02-21-2014, 03:08 AM   #2
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QuoteOriginally posted by Eder Quote
does anyone knows if filter is special or is normal. Cuz i read on a page that filter is non-rotating for this lens, is this true or not
http://www.photozone.de/pentax/129-pentax-smc-d-fa-100mm-f28-macro-review--test-report

Can i use a std 49mm fitler or must be non rotating?
You can use standard 49mm filter. The 'non-rotating' means that when focusing, the filter does not rotate.

In some lenses, the filter rotates when focusing. This is mainly a problem with polarizing filters, where the rotation changes polarization.
02-21-2014, 09:55 AM   #3
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Autofocus non-rotating

QuoteOriginally posted by ppohja Quote
You can use standard 49mm filter. The 'non-rotating' means that when focusing, the filter does not rotate.

In some lenses, the filter rotates when focusing. This is mainly a problem with polarizing filters, where the rotation changes polarization.
Pentax user's manual says that when using autofocus, lens do not rotate. so this means that i need a non-rotating polarizer filter when i use autofocus?
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02-21-2014, 12:00 PM   #4
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An ordinary polarizer is fine with this lens. Almost all lenses are like the DFA 100mm f2.8 Macro, with a filter ring that doesn't turn when the lens focuses or zooms. Then you can adjust the polarizer first. A handful of lenses have filter rings that turn when the lens is focused. For those lenses, you would have to focus the lens first, then adjust the polarizer. The Pentax-F 70-210mm f4-5.6 is one lens with filter ring that turns. I have never seen a non-rotating polarizer. The polarizer's position depends on the light direction and your angle to it, so it needs to rotate.

The user manual for the DFA 100mm f2.8 Macro is mostly concerned about the focus ring mechanism. You can't autofocus and manually focus at the same time.

02-21-2014, 06:10 PM   #5
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Using a polarizing filter on rotating filter mount lens isn't a huge problem, because you'd typically check the orientation of the filter between dissimilar shots anyway. And if the focus doesn't change that much, the threads won't rotate enough to make much difference. Orienting the polarizer is almost always a somewhat imprecise process, so it's not like if the ring moves a few degrees when focusing it's typically going to matter that much.
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