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Polarising filter with UV filter?

 
 
Randall Ainsworth
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      11-16-2006
In article <(E-Mail Removed)>, Stimp
<(E-Mail Removed)> wrote:

> I recently bought a UV filter for the 17-85mm lens I bought, and I'm
> considering whether or not to buy a polarising filter too.
>
> When using a polarising filter is it normal to remove the UV filter
> first, or do you mix the two?
>
> When would you generally use a polarising filter? Would you leave the
> filter on all the time, or only in specific lighting?

z
Oh, just stack as many pieces of glass in front of the lens as you can.
 
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acl
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      11-16-2006

David Littlewood wrote:
> The quarter wave plate which circular polarisers have after the
> polariser absorb no significant amount of light, so the difference in
> absorption between the two is negligible.
>


Now that you mention it, introducing a phase difference shouldn't
necessarily cost anything in terms of transmission. I had assumed it
does. So, do you know why there is extra loss (most polarisers I've
seen lose closer to two stops)?

Thanks.

 
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Phil Wheeler
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      11-16-2006
Randall Ainsworth wrote:
> In article <(E-Mail Removed)>, Stimp
> <(E-Mail Removed)> wrote:
>
>> I recently bought a UV filter for the 17-85mm lens I bought, and I'm
>> considering whether or not to buy a polarising filter too.
>>
>> When using a polarising filter is it normal to remove the UV filter
>> first, or do you mix the two?
>>
>> When would you generally use a polarising filter? Would you leave the
>> filter on all the time, or only in specific lighting?

> z
> Oh, just stack as many pieces of glass in front of the lens as you can.



Only issue may be vignetting.

Phil
 
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Ken Lucke
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      11-16-2006
In article <(E-Mail Removed)>, acl
<(E-Mail Removed)> wrote:

> Ken Lucke wrote:
> > In article <(E-Mail Removed)>, Stimp
> > <(E-Mail Removed)> wrote:
> >
> >>I recently bought a UV filter for the 17-85mm lens I bought, and I'm
> >>considering whether or not to buy a polarising filter too.

> >
> > My opinion (and that of my 28-year veteran mentor): Don't. Just use
> > the polarizer - even when it's not doing a lot of polarizing, it still
> > functions just as well to "cut haze" which, besides "protecting the
> > lens" [which, BBTW, a polarizer does just as well] is the main thing
> > that people get sucked into buying a UV filter for.

>
> It also cuts two stops of light, though. If you don't find this
> important, I suppose you live in a very sunny place and never shoot
> except in bright light or with a tripod.


Tripod. 99.999% of the time. I think I also said "unless I really
need the 2/3 [sic] stops"

>
> > Mine is there at all times, unless I really need the 2/3 stop of extra
> > light that it cuts out. I like to shoot underexposed by one stop
> > normally anyway [so I have more exposure play room in post and better
> > saturation], so it about evens things out, shutter-speed-wise.

>
> 2/3 stop? Are you sure about this? I mean, did you check? What kind of
> polariser is this?


My fat fingering: I was writing in a hurry. Let that read 2-3 instead
of 2/3. Mea culpa.

> >
> > You'd be surprised how much glare it cuts out on just standard shots
> > (like wet leaves, damping down highlights to a manageable level on
> > rippled water, etc., even on a cloudy day reflections off of interior
> > objects, the list goes on and on...), and how much it brings up the
> > saturation of color in many shots.

>
> >
> >
> >>Also what features should I make sure the filter has before I buy it?
> >>(e.g. circular polarisers are apparently better etc)

> >
> > Circular is not "better" than linear. [Actually, IMO, linear is
> > considerably better than circular in side-by-side comparisons I have
> > made]. Circulars have to polarize the light, then re-orient it again
> > before passing it on - linears don't have that extra step. They were
> > designed differently because auto-focus film cameras use a different
> > method of sharing the image between the focus/viewfinder/meter than
> > non-autofocus cameras. There's all sorts of techincal information on
> > this issue if you Google for it.

>
> Well, if he has an SLR, he'll probably have problems with AF
> (beamsplitters are used for this and a linear polariser will mess it up).


_Most_ digitals don't use beamsplitting AF, AFAIK. He was talking
about a digital. I've been able to use a linear on every digital I've
ever tried. Googling the subject [as you made me doubt my experiences
as semi-unique] seems to find almost universal agreement to that
opinion.

> And circular polarisers don't "re-orient" the light before passing it
> on, but since you dislike nitpicking, forget I ever wrote that!


Uhm, a circular polarizer nothing more than a linear polarizer with the
addition of a followingy 1/4 wave plate - I'd call a 1/4 wave plate
"reorienting", but then I guess I'm funny that way.

> >
> > Most digital cameras can use either linear or circular. Circular is
> > what you are likely to find more of, because most recent [auto-focus]
> > film cameras needed them.

>
> Maybe cameras with contrast detection AF will work, I don't know. But
> all SLRs I know of use phase detection AF and this uses mirrors; you'll
> need a circular polariser for them. But maybe some have no problem with
> linear polarisers, I can't say for sure.


See above.

> Perhaps it would be best if the OP tested AF and metering with a linear
> polariser should he decide to get one instead of circular.
>
> >
> >
> > DON'T skimp and buy a cheapie. It's going to be one of the MOST
> > important additions you can put on your camera/lens. Buy one
> > commensureate with the best glass you are going to be using it on -
> > it's high crime to use, say a Canon L series lens, then stick a cheapie
> > polarizer out in front of it. If you are going to be using several
> > sizes of lenses, buy the Cokin system and adapter rings, that way you
> > only have to have one polarizer to be shared between them.

>
> That's also good advice.

 
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Ken Lucke
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Posts: n/a
 
      11-16-2006
In article <1hounwr.17hzsaamhlkwN%(E-Mail Removed)0m>, Paul Mitchum
<(E-Mail Removed)0m> wrote:

> Ken Lucke <(E-Mail Removed)> wrote:
>
> > [My polarizing filter] is there at all times, unless I really need the 2/3
> > stop of extra light that it cuts out. I like to shoot underexposed by one
> > stop normally anyway [so I have more exposure play room in post and better
> > saturation], so it about evens things out, shutter-speed-wise.

>
> If the filter is on your lens, and you have through-the-lens metering,
> then you're not underexposing anything, it seems to me.


Uhm... I think I said "...evens things out, _shutter-speed-wise_".
 
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Ken Lucke
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Posts: n/a
 
      11-16-2006
In article <(E-Mail Removed)>, acl
<(E-Mail Removed)> wrote:

> acl wrote:
> >
> >> Mine is there at all times, unless I really need the 2/3 stop of extra
> >> light that it cuts out. I like to shoot underexposed by one stop
> >> normally anyway [so I have more exposure play room in post and better
> >> saturation], so it about evens things out, shutter-speed-wise.

> >
> > 2/3 stop? Are you sure about this? I mean, did you check? What kind of
> > polariser is this?
> >

>
> OK, it's impossible for it to only cut 2/3 of a stop. It will cut 1 if
> it's a linear polariser with perfect transmission for fully polarised light.
>

As I just noted in another article, I meant "2-3" not 2/3. I was in a
hurry and didn't proofread my own stuff like I normally do. My
apologies for starting this furor.

> A perfect linear polariser would transmit a fraction cos(theta)^2 of
> light which is incident on it and polarised at an angle theta to the
> angle which it passes. So for unpolarised light it'll be the integral of
> this from 0 to 2 pi, divided by 2 pi, ie 1/2. This is one stop. And
> circular polarisers will cut more.


Yeah, well. OK. You guys can worry about the math. I'll just go take
pictures. =:^)

> I suppose a linear polariser could also pass light polarised at other
> angles, and this would cut less light.


Singh-Ray has a circular polarizer they call "LB" (Lighter and
Brighter) that is rated at only 1 1/3 stops. Only trouble is (in my
view), they also combine it with a built-in warming filter, and I don't
necessarily want that. I suppose I could compensate in post, but I'd
rather not.
 
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David Littlewood
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Posts: n/a
 
      11-16-2006
In article <(E-Mail Removed). com>, acl
<(E-Mail Removed)> writes
>
>David Littlewood wrote:
>> The quarter wave plate which circular polarisers have after the
>> polariser absorb no significant amount of light, so the difference in
>> absorption between the two is negligible.
>>

>
>Now that you mention it, introducing a phase difference shouldn't
>necessarily cost anything in terms of transmission. I had assumed it
>does. So, do you know why there is extra loss (most polarisers I've
>seen lose closer to two stops)?
>
>Thanks.
>

The polarising material does not have a perfect transmission of light
whose polarisation is aligned with its maximum transmission axis. Thus
it absorbs something like 99% of the light transverse to this axis and
say 25-50% of the light aligned with it. The better quality the filter,
the lower this additional (unwanted) absorption is likely to be.

In addition, there is the factor I mentioned before - one deliberately
aligns the filter to block polarised light from non-specular reflections
(which is polarised. IOW, the incoming light is partially polarised, and
one seeks to preferentially block it.

David
--
David Littlewood
 
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acl
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Posts: n/a
 
      11-16-2006

Ken Lucke wrote:
> In article <(E-Mail Removed)>, acl
> <(E-Mail Removed)> wrote:
>
> > Ken Lucke wrote:
> > > In article <(E-Mail Removed)>, Stimp
> > > <(E-Mail Removed)> wrote:
> > >
> > >>I recently bought a UV filter for the 17-85mm lens I bought, and I'm
> > >>considering whether or not to buy a polarising filter too.
> > >
> > > My opinion (and that of my 28-year veteran mentor): Don't. Just use
> > > the polarizer - even when it's not doing a lot of polarizing, it still
> > > functions just as well to "cut haze" which, besides "protecting the
> > > lens" [which, BBTW, a polarizer does just as well] is the main thing
> > > that people get sucked into buying a UV filter for.

> >
> > It also cuts two stops of light, though. If you don't find this
> > important, I suppose you live in a very sunny place and never shoot
> > except in bright light or with a tripod.

>
> Tripod. 99.999% of the time. I think I also said "unless I really
> need the 2/3 [sic] stops"
>
> >
> > > Mine is there at all times, unless I really need the 2/3 stop of extra
> > > light that it cuts out. I like to shoot underexposed by one stop
> > > normally anyway [so I have more exposure play room in post and better
> > > saturation], so it about evens things out, shutter-speed-wise.

> >
> > 2/3 stop? Are you sure about this? I mean, did you check? What kind of
> > polariser is this?

>
> My fat fingering: I was writing in a hurry. Let that read 2-3 instead
> of 2/3. Mea culpa.
>
> > >
> > > You'd be surprised how much glare it cuts out on just standard shots
> > > (like wet leaves, damping down highlights to a manageable level on
> > > rippled water, etc., even on a cloudy day reflections off of interior
> > > objects, the list goes on and on...), and how much it brings up the
> > > saturation of color in many shots.

> >
> > >
> > >
> > >>Also what features should I make sure the filter has before I buy it?
> > >>(e.g. circular polarisers are apparently better etc)
> > >
> > > Circular is not "better" than linear. [Actually, IMO, linear is
> > > considerably better than circular in side-by-side comparisons I have
> > > made]. Circulars have to polarize the light, then re-orient it again
> > > before passing it on - linears don't have that extra step. They were
> > > designed differently because auto-focus film cameras use a different
> > > method of sharing the image between the focus/viewfinder/meter than
> > > non-autofocus cameras. There's all sorts of techincal information on
> > > this issue if you Google for it.

> >
> > Well, if he has an SLR, he'll probably have problems with AF
> > (beamsplitters are used for this and a linear polariser will mess it up).

>
> _Most_ digitals don't use beamsplitting AF, AFAIK. He was talking
> about a digital. I've been able to use a linear on every digital I've
> ever tried. Googling the subject [as you made me doubt my experiences
> as semi-unique] seems to find almost universal agreement to that
> opinion.


Well, a digital for which he bought a 17-85mm lens. So I assumed an
SLR, all of which use phase detection AF, as far as I know. Which may
or may not work with linear polarisers (I never tried, but would expect
them not to; but maybe I am wrong).

>
> > And circular polarisers don't "re-orient" the light before passing it
> > on, but since you dislike nitpicking, forget I ever wrote that!

>
> Uhm, a circular polarizer nothing more than a linear polarizer with the
> addition of a followingy 1/4 wave plate - I'd call a 1/4 wave plate
> "reorienting", but then I guess I'm funny that way.


No, you're wrong, not funny. It introduces a phase difference between
two directions. Sorry to pick nits.

Anyway, not much point in going on and on about this.

 
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acl
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Posts: n/a
 
      11-16-2006

David Littlewood wrote:
> In article <(E-Mail Removed). com>, acl
> <(E-Mail Removed)> writes
> >
> >David Littlewood wrote:
> >> The quarter wave plate which circular polarisers have after the
> >> polariser absorb no significant amount of light, so the difference in
> >> absorption between the two is negligible.
> >>

> >
> >Now that you mention it, introducing a phase difference shouldn't
> >necessarily cost anything in terms of transmission. I had assumed it
> >does. So, do you know why there is extra loss (most polarisers I've
> >seen lose closer to two stops)?
> >
> >Thanks.
> >

> The polarising material does not have a perfect transmission of light
> whose polarisation is aligned with its maximum transmission axis. Thus
> it absorbs something like 99% of the light transverse to this axis and
> say 25-50% of the light aligned with it. The better quality the filter,
> the lower this additional (unwanted) absorption is likely to be.


OK I see. I thought they could be made perfect.
Thanks.

 
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John McWilliams
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      11-16-2006
acl wrote:
> Ken Lucke wrote:
>> In article <(E-Mail Removed)>, acl

>
>>> And circular polarisers don't "re-orient" the light before passing it
>>> on, but since you dislike nitpicking, forget I ever wrote that!

>> Uhm, a circular polarizer nothing more than a linear polarizer with the
>> addition of a followingy 1/4 wave plate - I'd call a 1/4 wave plate
>> "reorienting", but then I guess I'm funny that way.

>
> No, you're wrong, not funny. It introduces a phase difference between
> two directions. Sorry to pick nits.
>
> Anyway, not much point in going on and on about this.


But, but, uh, this is usenet! There's lots of going on and on about just
any old thing. And this is on topic.

Don't stop now!

--
john mcwilliams
 
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