Polarizing Filters

[stripe]

Hello,

I was just wondering about people's experiences with polarizing filters. Do you find they are worth the investment? From my limited research it seems their main benefit is cutting through haze and enhancing greens and blues (in addition to eliminating reflections).

Do you have one? How often do you use it? What are your main applications for this filter?

[Sahil]

Try this link. Might be of some help to you.

[Colin Southern]

Do you have one?

I have 2

How often do you use it?

Never.

What are your main applications for this filter?

N/A

[Donald]

Do you have one?

Yes. Cokin 'P' circular

How often do you use it?

Rarely. When I came back to photography 18 months ago, what I'd been reading told me it was an absolute 'must have' for the aspiring landscape photographer. And there are many who hold to that view. A forum I dabbled in a long time ago had subscribers whose every image was made with a polariser mounted. They just didn't seem to photograph without one.

What are your main applications for this filter?

I think the only thing I would use it for would be with a very blue sky and fluffy white clouds. But I'm not sure I'd be making an image featuring those any more.

It very much depends on your own vision and intent for your photography. What is it you want to produce and would a polariser help you achieve that aim? I wish I'd been part of this forum, getting the sort of advice that's offered. I'd have saved myself a lot of money that would have been better spent on more ND and GND filters.

[Colin Southern]

what I'd been reading told me it was an absolute 'must have' for the aspiring landscape photographer. And there are many who hold to that view. A forum I dabbled in a long time ago had subscribers whose every image was made with a polariser mounted. They just didn't seem to photograph without one.

That might explain why my landscapes are so bad

I think the only thing I would use it for would be with a very blue sky and fluffy white clouds.

To be honest Donald, I think a lot of folks would get much the same result by simply knocking back their exposure 1 to 2 stops.

[Donald]

That might explain why my landscapes are so bad

Yep, that definitely looks like the cause. But stay on this forum and you'll learn how to do it!

To be honest Donald, I think a lot of folks would get much the same result by simply knocking back their exposure 1 to 2 stops.

Agreed

[Steaphany]

Do you find they are worth the investment?

Yes, when you understand when light from an object in front of your lens is and is not polarized, a polarizing filter provides a level of control that you can't achieve by any other means.

First off, you need to understand what polarization of light means. All light, when examined at the level of the individual photons, is polarized. The photon comprises both electric and magnetic fields that are perpendicular to each other and both of these are also perpendicular to the direction of the photons travel.

Light, in terms of scene illumination, is considered unpolarized when the electric and magnetic field orientation of each photon is randomly orientated to the total number of photons. Some will be vertical, horizontal, and everything in between. Light is considered polarized when a majority of the photons all have their electric and magnetic field orientations aligned.

There also is another form of polarization that needs to be considered, Circular Polarization. Just as the planes of the electric and magnetic fields can remain fixed, there is also a condition where they constantly spin, either clockwise or counter clockwise, about the axis of travel as the photon moves.

Circular polarization is the condition of light that exits a circular polarizing filter. The reason is modern SLR cameras have difficulty with incoming polarized light. The remedy is to provide a filter that consists of two components. First is the actual polarizer that filters light of a specific orientation followed by a 1/4 wave plate or retarder which turns the linearly polarized light into circularly polarized light. Though still effectively polarized, circularly polarized light does not cause problems with the camera's operation.

From my limited research it seems their main benefit is cutting through haze and enhancing greens and blues (in addition to eliminating reflections).

The effect of cutting through haze and increasing the natural color saturation, all colors - not just greens and blues, is highly selective on the angle between the incoming Sun light and the optical axis of your camera. For an optimal effect, the angle needs to be 90º. When the Sun's rays enter the Earth's atmosphere, they are scattered by dust particles, water vapor, and by the air. The portions of this scattered light that proceeds at right angles to the Sun's rays are strongly polarized.

This means that the polarization angle will vary through out the day as the Sun moves across the sky. In the mornings and evenings, the greatest effect is when your camera is aimed at a subject to the North or South. At midday, when most photographers don't bother to go out shooting because the light is too harsh and shadows small to nonexistent, the polarization will be greatest in all directions since the horizon is nearly perpendicular to the incoming Sun light.

To Darken the Sky, Cut through Haze, and Increase Color Saturation
Position your camera relative to the scene so that the Sun is at a 90º angle. Now, while looking through the view finder of your camera, adjust the orientation of your polarizing filter by rotating the adjustment ring to darken the sky as much as possible. You will see that at one orientation, the sky is bright and with a 90º turn of the filter, it will be dark. Continuing an additional 90º turn will bring the sky bright again. Just work and find the position that yields the darkest sky. When conditions are exceptionally clear with the Sun at the right angle, you can record a brightly lit scene with a sky that is deep blue to nearly black.

Exposure Control
This is where you stack two polarizing filters, but for this to work, one must be a traditional polarizer. It will not work with two stacked circular polarizers. Place your circular polarizing filter on first and then add the linear polarizer. Now you have an adjustable neutral density filter that you can tune from two stops all the way down to ten stops.

Contrast Control
A polarizing filter may be used to control the relative brightness of some scenes without changing the lighting. Such subjects include the roofs and walls of buildings, landscapes, and views that include both water and sky. For example, suppose the subject is a ship against the sea and sky. The light from the sea and sky is partly polarized while the light from the ship is unpolarized. By rotating the polarizing filter, you can select a position which reduces the sea and sky glare and enhancing the contrast of the ship.

Glare Reduction
When ever light strikes a flat surface at a low enough angle, the reflected light becomes highly polarized. When your polarizer is oriented to block these reflections, you can reduce or at times completely eliminate there surface reflections.

Do you have one?

Yes

How often do you use it?

All depends on the scene, lighting, and my needs at the time.

What are your main applications for this filter?

See my write up above.

[Shadowman]

I use it for shooting sunsets, afternoon settings, and I purchased it to give skies an extra burst of blue. I also shoot the same settings without, only with a different camera and for shots that I know will be overexposed, I usually use a shorter shutter speed. I also read that the CP filter helps reduce reflections in windows but I have yet to try it for that reason.

[Colin Southern]

From my limited research it seems their main benefit is cutting through haze and enhancing greens and blues (in addition to eliminating reflections).

I might add that the enhancing of colours can be a very real benefit - but - what's really happening is the reduction of glare, usually caused by direct / full sunlight. However ... if you want to shoot world-class landscape then you'll never ever shoot in full sunlight - you HAVE to shoot in the "golden hour" around dawn / dusk. And if you do, then you won't have the issues with glare that you'd have needed a CP for in the first place.

So from my point of view, all a CP is doing most of the time is trying to compensate for shooting at the wrong time of day.

[Klickit]

So from my point of view, all a CP is doing most of the time is trying to compensate for shooting at the wrong time of day.

But...sometimes you will see something that can't wait - eg a thunderstorm approaching - and then, shooting at the "wrong" time of day is perfectly justified and aids like polarisers are good to have. Hmmm??

[Colin Southern]

But...sometimes you will see something that can't wait - eg a thunderstorm approaching - and then, shooting at the "wrong" time of day is perfectly justified and aids like polarisers are good to have. Hmmm??

Absolutely possible ... but I personally can't see what advantage a CP would give when photographing an approaching thunderstorm. I'm not trying to say that people shouldn't use them or that they're a waste of money, but what I can say is that I seem to do OK with out them, and they were certainly a big waste of my money (about $600 for the two of them).

[Steaphany]

I personally can't see what advantage a CP would give when photographing an approaching thunderstorm.

If the conditions are midday plus or minus 3 hours, allowing the light of the sky around the horizon to have a significant level of polarization, then shooting the storm through a polarizer would allow you to adjust the sky brightness leaving the cloud brightness unchanged. The shot would contain less haze from Sun light scattered between you and the storm thus improving clarity and detail, remember at 90º to the Sun, this light is polarized. The clouds would stand out better due to greater contrast with the background sky.

These are all factors I feel that makes a polarizer necessary, besides, with out one in your kit, no other optical or software method could provide this result so easily.

[Sunray]

So from my point of view, all a CP is doing most of the time is trying to compensate for shooting at the wrong time of day.

I would say a CP is also tool for compensating shootings at the wrong season of the year.

During summertime in germany the sky gets often hazy or overcast after a few days of nice and hot weather. On some days it even gets hazy before noon and it will not get any better during the rest of the day. In such cases a CP will save your day here, if you are going to get a picture with blue sky in the background.

bye
Robert

[Colin Southern]

If the conditions are midday plus or minus 3 hours, allowing the light of the sky around the horizon to have a significant level of polarization, then shooting the storm through a polarizer would allow you to adjust the sky brightness leaving the cloud brightness unchanged. The shot would contain less haze from Sun light scattered between you and the storm thus improving clarity and detail, remember at 90º to the Sun, this light is polarized. The clouds would stand out better due to greater contrast with the background sky.

These are all factors I feel that makes a polarizer necessary, besides, with out one in your kit, no other optical or software method could provide this result so easily.

Sounds good in theory, however in practice I find that polarisers improve cloud detail mostly due to reducing their exposure (ie moving it from, say, zone 10 (no detail) to zone 8 or 9). If people dialed in a couple of stops of -ve EC they get close to the same detail -- and if they use low amount / high radius sharpening they can achieve a good amount of "pop" too.

Additionally, if one wants to darken the sky but leave the sky untouched then it's a trivial thing to do in post-processing these days (you don't even need selections) (although having said that, under-exposing the sky also does just as good a job). In fact, adjusting in PP often works BETTER in that it's consistent whereas a polariser on a wide-angle lens will give all sorts of unevenness in the sky.

[Peter Ryan]

I do have one and use it in two main areas.

I always shoot rainforest on a bright overcast day but there is still significant glare off the foliage and a polariser cuts this out and helps saturate colours.

The other time I use a polariser a lot is in Central Australia on the red dirt. It has a lot of glare and polariser cuts this and adds geat colour to the red dirt and the blue sky.

As the others have said it depends on the light a lot as well. If you use it when it is not appropriate or necessary, some I see leave it on all the time, you are only losing 1.7 stops of light so making your lens much slower. Having said that I have used it as a neutral density filter when I needed to slow the shutter down further.

Practice and see where it works for you but don't leave it on the lens all the time.

[Radu Dinu Cordeanu]

Hi,
All of You have Your right.
Below You have my perspective





Thank You for understanding
Radu Dinu

[David]

This is an interesting and perennial topic with opinions, as noted above, divided. I'm definitely on the side of the CP fans and have posted some photos previously:

New Zealand Lake Wanaka Circular Polarisation

Those images from New Zealand rely on the 90 degree effect, as explained by Steaphany, and were shot when the Sun had just risen, again maximising the effect.

In my view, such filters can be very useful indeed, and I don't subscribe to Colin's view that altering exposure can lead to the same or similar effects. One application that has not been discussed is the use in reducing glare or reflections on water. The matter came up on my recent trip to Northern Cyprus and I illustrated the point to my companions with the following two shots. (I make no pretence to artistic merit in these.)



This first shot has no polarisation filter. The sea is very much as the eye sees it - more or less opaque.



With this shot the CP filter is in use. Now details under the surface of the sea have appeared. The effect is independent of the position of the sun because the glare is from the sea. I think this latter shot has more interest than the former and I don't think that changing exposures would make any difference.

Thus, to me polarisation filters are an essential part of my kit.

Cheers

David

[Colin Southern]

This is an interesting and perennial topic with opinions, as noted above, divided. I'm definitely on the side of the CP fans and have posted some photos previously:

New Zealand Lake Wanaka Circular Polarisation

Although ...

... both photos in that thread have the classic uneven sky typical of CP use, and many skys look under-saturated simply because they're washed out (ie a degree of over-exposure).

Still not convinced

[Shadowman]

David,

I think something else was changed in the second photo, which is partially why Colin isn't convinced. Shouldn't the CP filter have darkened the sky? And also, the foreground is everexposed which wouldn't happen with a CP filter. Did you change your exposure time for the second photo?

This is an interesting and perennial topic with opinions, as noted above, divided. I'm definitely on the side of the CP fans and have posted some photos previously:

New Zealand Lake Wanaka Circular Polarisation

Those images from New Zealand rely on the 90 degree effect, as explained by Steaphany, and were shot when the Sun had just risen, again maximising the effect.

In my view, such filters can be very useful indeed, and I don't subscribe to Colin's view that altering exposure can lead to the same or similar effects. One application that has not been discussed is the use in reducing glare or reflections on water. The matter came up on my recent trip to Northern Cyprus and I illustrated the point to my companions with the following two shots. (I make no pretence to artistic merit in these.)



This first shot has no polarisation filter. The sea is very much as the eye sees it - more or less opaque.



With this shot the CP filter is in use. Now details under the surface of the sea have appeared. The effect is independent of the position of the sun because the glare is from the sea. I think this latter shot has more interest than the former and I don't think that changing exposures would make any difference.

Thus, to me polarisation filters are an essential part of my kit.

Cheers

David

[Dave Humphries]

I think something else was changed in the second photo, which is partially why Colin isn't convinced.

Hi Shadowman,

Looking at the EXIF for each;
without filter:
# Exposure Time (1 / Shutter Speed) = 1/60 second ===> 0.01667 second
# Lens F-Number / F-Stop = 22/1 ===> ƒ/22
# ISO Speed Ratings = 400
# EXIF Version = 0221
# Original Date/Time = 2010:07:14 10:26:53
# Digitization Date/Time = 2010:07:14 10:26:53
# Components Configuration = 0x01,0x02,0x03,0x00 / YCbCr
# Shutter Speed Value (APEX) = 393216/65536
Shutter Speed (Exposure Time) = 1/64 second
# Aperture Value (APEX) = 589824/65536
Aperture = ƒ/22.63
# Exposure Bias (EV) = 0/1 ===> 0
# Flash = Flash did not fire, compulsory flash mode
# Focal Length = 24/1 mm ===> 24 mm

With filter:
# Exposure Time (1 / Shutter Speed) = 1/20 second ===> 0.05 second
# Lens F-Number / F-Stop = 22/1 ===> ƒ/22
# ISO Speed Ratings = 400
# EXIF Version = 0221
# Original Date/Time = 2010:07:14 10:26:23
# Digitization Date/Time = 2010:07:14 10:26:23
# Components Configuration = 0x01,0x02,0x03,0x00 / YCbCr
# Shutter Speed Value (APEX) = 292864/65536
Shutter Speed (Exposure Time) = 1/22.14 second
# Aperture Value (APEX) = 589824/65536
Aperture = ƒ/22.63
# Exposure Bias (EV) = 0/1 ===> 0
# Flash = Flash did not fire, compulsory flash mode
# Focal Length = 24/1 mm ===> 24 mm

All I see is the shutter speed changing from 1/60 to 1/20, as you expect, by about 2 stops, a little less in fact.
I can't see the PP or RAW conversion settings, but that may explain the foreground difference.

Shouldn't the CP filter have darkened the sky?

No, because that would be a different plane of polaristion to the sea.

A potential third shot with polariser set for max. sky difference would show that, but also less effect on the sea.

One filter can't normally* do both at once, but with 24mm focal length, setting for the sky would give the uneven sky effect, which, to be honest I think is negligible on this second shot when compared to first. It certainly what I would call the classic problem, since it is nowhere near as bad as when someone tries to use the CPL to darken the sky on say, and 18mm (27mm equiv.) shot.

* OK, there will be certain compass orientations of sea/lake/river view in combination with sun angle that lead to it having a significant effect on both, but I feel it is less likely to be a problem in practice.

Cheers,