Polarising filters
Discussion
Given that you can use linear polarisers on non-AF cameras, and need to use circular polarisers on AF cameras, would I be correct in thinking there are no down-sides to using a circular polariser on a non-AF camera ?
I'm assuming it would still produce exactly the same effect, but have never really understood the why an AF camera needed a circular polariser for the AF to be able to function, which made me wonder if they may produce very slightly different results.
Nick M said:
Given that you can use linear polarisers on non-AF cameras, and need to use circular polarisers on AF cameras, would I be correct in thinking there are no down-sides to using a circular polariser on a non-AF camera ?
I would think so.Nick M said:
I'm assuming it would still produce exactly the same effect, but have never really understood the why an AF camera needed a circular polariser for the AF to be able to function
Because AF systems are (apparently though I haven't tried it) rendered inaccurate by operating through a linear polarised filter.For sure you get what you pay for. Optical quality matters here as much as with the lens itself. Hoya is well worth looking at with different ranges to suit budgets including some coated specifically for digital. B&W are another top make.
A bit lower down the market I recently found this Hama 77mm (which happens to fit all my lenses), not quite the quality of the market leaders but with 60%+ off RRP you can apparently get more than you pay for at present.
A bit lower down the market I recently found this Hama 77mm (which happens to fit all my lenses), not quite the quality of the market leaders but with 60%+ off RRP you can apparently get more than you pay for at present.
muppetdave said:
Slightly O/T, but would people here generally agree you get what you pay for with Circ. Polarisers? I have a relatively cheap one for my smaller diameter lenses, but need to get one for my 72mm 70-200. I'm not sure whether or not to go budget or more expensive.
What brand of lens ? I only ask because none of the Canon, Nikon or Sigma 70-200 lenses have a 72mm filter thread. Most of them (the f2.8 lenses) are 77mm and the Canon f4 is 67mm.Just didn't want you getting the wrong size.
As for quality, yes, you get what you pay for.
I mostly use B+W or Heliopan filters, but Hoya seem to get good comments too.
RobDickinson said:
AF typicaly works on phase change detection, liniar polariser will remove that so thats why it stops AF working.
Should be fine going the other way.
Didn't understand a word of that Should be fine going the other way.
, but thanks for confirming it should be fine to use a circular polariser on a non-AF camera 
Nick M said:
RobDickinson said:
AF typicaly works on phase change detection, liniar polariser will remove that so thats why it stops AF working.
Should be fine going the other way.
Didn't understand a word of that Should be fine going the other way.
, but thanks for confirming it should be fine to use a circular polariser on a non-AF camera Long story short: I came by a Hoya polarising filter, NOT a circular P, which I fitted to a 180mm Nikkor I used to own. Blow me down, the combination focussed spot on, every time without a hitch.
Now there is the slight possibility that the filter left the Hoya factory without somebody stamping "Circular" all round the side, but otherwise I've always been left thinking "well, how the hell does that work then?"
from Wiki:
"There are two types of polarizing filters generally available, linear and circular. With the exception of how they interact with some autofocus and metering mechanisms, they have exactly the same effect photographically. The metering and auto-focus sensors in certain cameras, including virtually all auto-focus SLRs, will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent. Circular polarizers include a linear polarizer on the front, which selects one polarization of light while rejecting another, followed by a quarter-wave plate, which converts the selected polarization to circularly polarized light inside the camera, which works with all types of cameras, because mirrors and beam-splitters split circularly polarized light the same way they split unpolarized light."
"There are two types of polarizing filters generally available, linear and circular. With the exception of how they interact with some autofocus and metering mechanisms, they have exactly the same effect photographically. The metering and auto-focus sensors in certain cameras, including virtually all auto-focus SLRs, will not work properly with linear polarizers because the beam splitters used to split off the light for focusing and metering are polarization-dependent. Circular polarizers include a linear polarizer on the front, which selects one polarization of light while rejecting another, followed by a quarter-wave plate, which converts the selected polarization to circularly polarized light inside the camera, which works with all types of cameras, because mirrors and beam-splitters split circularly polarized light the same way they split unpolarized light."
I got as far as...
RobDickinson said:
from Wiki:
"There are two types of polarizing filters generally available, linear and circular. With the exception of how they interact with some autofocus and metering mechanisms, they have exactly the same effect photographically...."
Cheers Rob for the clarification "There are two types of polarizing filters generally available, linear and circular. With the exception of how they interact with some autofocus and metering mechanisms, they have exactly the same effect photographically...."
Nick M said:
muppetdave said:
Slightly O/T, but would people here generally agree you get what you pay for with Circ. Polarisers? I have a relatively cheap one for my smaller diameter lenses, but need to get one for my 72mm 70-200. I'm not sure whether or not to go budget or more expensive.
What brand of lens ? I only ask because none of the Canon, Nikon or Sigma 70-200 lenses have a 72mm filter thread. Most of them (the f2.8 lenses) are 77mm and the Canon f4 is 67mm.Just didn't want you getting the wrong size.
As for quality, yes, you get what you pay for.
I mostly use B+W or Heliopan filters, but Hoya seem to get good comments too.
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