Polarising Filter

[stapo49]

As I understand it a polarising filter doesn't have any effect on your image if the sun is directly behind or in front of you but works at 90 degrees to where you are shooting from? So this would rule it out for sunset/sunrise photography? Or can it?

So I was wondering how and when this type of filter is used?

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[Original katomi]

Never tried but I do know that wide angle lens are a problem as the effect varies

 

[Original katomi]

The filter can be used to take off reflection off water /glass and make the sky a deeper blue
You can get screw on or square that fits in a holder
Depends on how and what you plan to do
I use round as most of my lenses have the same thread size
If I cam help give me a shout

 

[smoke665]

As I understand it a polarising filter doesn't have any effect on your image if the sun is directly behind or in front of you but works at 90 degrees to where you are shooting from? So this would rule it out for sunset/sunrise photography? Or can it?

So I was wondering how and when this type of filter is used?

Sent from my SM-G965F using Tapatalk

I've used my circular a few times when I had highly reflective surfaces to contend with or to deepen the blue in a sky. In all cases the closer the light or reflection is to 90 degrees the more the effect. You are correct that a straight on our from behind sun will have little effect, nor do they have much effect in low light situations. As to sunset/sunrise it would depend on the direction of the light/reflections and the effect you wanted. IE: suppose you had a red sun reflecting off the wet rocks on beach, would you want to eliminate that red light or keep it?

 

[stapo49]

As I understand it a polarising filter doesn't have any effect on your image if the sun is directly behind or in front of you but works at 90 degrees to where you are shooting from? So this would rule it out for sunset/sunrise photography? Or can it?

So I was wondering how and when this type of filter is used?

Sent from my SM-G965F using Tapatalk

I've used my circular a few times when I had highly reflective surfaces to contend with or to deepen the blue in a sky. In all cases the closer the light or reflection is to 90 degrees the more the effect. You are correct that a straight on our from behind sun will have little effect, nor do they have much effect in low light situations. As to sunset/sunrise it would depend on the direction of the light/reflections and the effect you wanted. IE: suppose you had a red sun reflecting off the wet rocks on beach, would you want to eliminate that red light or keep it?

Thanks for the info. It sounds like something you would use every now and again in a specific circumstance. I am mostly shooting longer exposures around sunset at the moment so ND and/or graduated filters probably more useful to me.

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[vintagesnaps]

Maybe what you're talking about or read about is using a circular polarizer that you can turn to 90 degrees, or 180, as you keep turning it. Those screw on to the front of the lens (at least ones I'm familiar with do) and turn to adjust from filtering less light to filtering more.

The polarizer cuts light coming into the camera and exposure needs to be adjusted accordingly for less light. You can see thru the viewfinder that it's darker when using an SLR and you're looking thru the lens (compared to using a rangefinder and not looking thru the lens).

A polarizer blocks horizontal rays of light that cause glare, that make us squint (although the rays aren't all directly horizontal as they travel at different angles). As you turn the polarizer it blocks those rays of light. Sunglasses that are polarized basically do the same thing, blocking those horizontal rays.

I've used one shooting B&W film when it's sunny, hazy, or near water to cut the glare. I don't suppose a polarizer cuts light coming from behind you, and I don't usually take pictures facing directly into the sun so I'm not sure how effective they are for that. At sunset you're losing light so I don't see a need to use one then. I don't do sunrise...

 

[stapo49]

Maybe what you're talking about or read about is using a circular polarizer that you can turn to 90 degrees, or 180, as you keep turning it. Those screw on to the front of the lens (at least ones I'm familiar with do) and turn to adjust from filtering less light to filtering more.

The polarizer cuts light coming into the camera and exposure needs to be adjusted accordingly for less light. You can see thru the viewfinder that it's darker when using an SLR and you're looking thru the lens (compared to using a rangefinder and not looking thru the lens).

A polarizer blocks horizontal rays of light that cause glare, that make us squint (although the rays aren't all directly horizontal as they travel at different angles). As you turn the polarizer it blocks those rays of light. Sunglasses that are polarized basically do the same thing, blocking those horizontal rays.

I've used one shooting B&W film when it's sunny, hazy, or near water to cut the glare. I don't suppose a polarizer cuts light coming from behind you, and I don't usually take pictures facing directly into the sun so I'm not sure how effective they are for that. At sunset you're losing light so I don't see a need to use one then. I don't do sunrise...

Yes that's the polariser I was thinking about. Might be something to consider using if I start to do more photographs in harsher light. Thanks.

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[RVT1K]

I have circular polarizer filters on several of my lenses but they only come into play outside.

The circular polarizer allows your to rotate the filter to "match" the angle of the sun. The effect can be quite dramatic and you will see it in the viewfinder as you move in and out of the sweet spot. When things are right, you can get amazingly deep blue skies in your shots. It can also help with reflections especially from water.

The only minor downside is if you have a lens hood on. That can make getting to the filter to rotate it difficult if not impossible. If I need the lens hood, I'll remove it, adjust the filter, and re-install it.

 

[smoke665]

The only minor downside is if you have a lens hood on. That can make getting to the filter to rotate it difficult if not impossible. If I need the lens hood, I'll remove it, adjust the filter, and re-install it.

The flexible/collapsible hoods work well for this. My solid hoods have sliding doors on the bottom, that snap in. When using the polarizer I snap them out, giving me access to rotate the filter. The down side is that awful easy to misplace that little door

 

[Dao]

1 additional note. Some lens's front lens element rotate when focus. With those lens, you may need to re-adjust the CPL after focus.

 

[JBPhotog]

There may be some confusion here in the terminology, there are two types of polarizers, circular and linear. They are typically both round and mounted in a threaded ring for mounting on the front of the lens with a rotating ring to align the polarized light with the filter. Circular polarizers are most common now due to TTL metering and AF models etc. that can be affected by linear polarizers. If you own older polarizers from the film days, they still work, but with the TTL and AF caveat, YMMV.

 

[Soocom1]

There may be some confusion here in the terminology, there are two types of polarizers, circular and linear. They are typically both round and mounted in a threaded ring for mounting on the front of the lens with a rotating ring to align the polarized light with the filter. Circular polarizers are most common now due to TTL metering and AF models etc. that can be affected by linear polarizers. If you own older polarizers from the film days, they still work, but with the TTL and AF caveat, YMMV.

let me expand on that for a moment so folks can understand what is mechanically going on.

From Wiki:
Polarizing filter (photography) - Wikipedia

"Types[edit]
There are two types of polarizing filters readily available, linear and "circular", which have exactly the same effect photographically. But 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. Linearly-polarized light may also defeat the action of the Anti-aliasing filter (Low-pass filter) on the imaging sensor.

"Circular" polarizing photographic filters consist of a linear polarizer on the front, with a quarter-wave plate on the back. The quarter-wave plate converts the selected polarization to circularly polarized light inside the camera. This works with all types of cameras, because mirrors and beam-splitters split circularly polarized light the same way they split unpolarized light.[7]

Linear polarizing filters can be easily distinguished from circular polarizers. In linear polarizing filters, the polarizing effect works (rotate to see differences) regardless of which side of the filter the scene is viewed from. In "circular" polarizing filters, the polarizing effect works when the scene is viewed from the male threaded (back) side of the filter, but does not work when looking through it backwards."

And THAT is critical with digital because of the grid system used for the sensor.

Another factor is this: Linear are literally like Venetian blinds. auto-focus systems in film cameras loose the ability to properly focus when the linear polarizer is attached and the lens rotates, causing literally half of the system to not work.

From another Wiki:
Polarizer - Wikipedia


Circular and linear polarizing filters for photography[edit]
Main article: Polarizing filter (photography)
Linear polarizing filters were the first types to be used in photography and can still be used for non-reflex and older single-lens reflex cameras (SLRs). However, cameras with through-the-lens metering (TTL) and autofocusing systems – that is, all modern SLR and DSLR– rely on optical elements that pass linearly polarized light. If light entering the camera is already linearly polarized, it can upset the exposure or autofocus systems. Circular polarizing filters cut out linearly polarized light and so can be used to darken skies or remove reflections, but the circular polarized light it passes does not impair through-the-lens systems.[13]

so when using a particular type of polarizer, the filter if linear will literally block light at specific angles/frequencies. whereas a circular allows the light to "polarized" but not prevent the linear aspect of the system to be blocked.
The difference between a knife and a corkscrew. They both cut, but do it in different ways.

 

[petrochemist]

Maybe what you're talking about or read about is using a circular polarizer that you can turn to 90 degrees, or 180, as you keep turning it. Those screw on to the front of the lens (at least ones I'm familiar with do) and turn to adjust from filtering less light to filtering more.

The polarizer cuts light coming into the camera and exposure needs to be adjusted accordingly for less light. You can see thru the viewfinder that it's darker when using an SLR and you're looking thru the lens (compared to using a rangefinder and not looking thru the lens).

A polarizer blocks horizontal rays of light that cause glare, that make us squint (although the rays aren't all directly horizontal as they travel at different angles). As you turn the polarizer it blocks those rays of light. Sunglasses that are polarized basically do the same thing, blocking those horizontal rays.

I've used one shooting B&W film when it's sunny, hazy, or near water to cut the glare. I don't suppose a polarizer cuts light coming from behind you, and I don't usually take pictures facing directly into the sun so I'm not sure how effective they are for that. At sunset you're losing light so I don't see a need to use one then. I don't do sunrise...

All polarizers block light depending on the lights polarization. For photography they are always provided in a rotating mount, so the affect can be adjusted to that desired by the photographer. Polarizing sunglasses assume you are vertical & wish to reduce the reflections. They can be used for photography too by simply holding them in front of the lens provided the lens is small enough.

Light is naturally polarized when reflected by most non metallic surfaces, especially water & glass, as well as when scattered in the atmosphere. The degree of polarization seen in the reflected light will depend on the angle the light hits the surface, with most occurring at 'Brewster's angle', the angle being dependent on the materials refractive index (it works out about 56° for glass & 53° for water). By aligning the filter appropriately these reflections can either be reduced OR increased.

Using 2 polarizers together can give a variable ND (the front one needs to be a linear polarizer rather than a CPL) when both are aligned the combination works just life a single polarizer, when at 90° to each other they block most light - if they were perfectly effective & perfectly out of alignment they'd block all light.

 

[vintagesnaps]

From what I understand a polarizer blocks? filters? (not sure what describes it best) horizontal rays of light rather than vertical ones, but they actually move at various angles (which is why as you turn the polarizer more/different rays of light are blocked/filtered - I think, I'm a teacher but not a scientist working in a laboratory...! lol). I've understood it to mean that the horizontal rays coming at that angle directly into our eyes are the ones that cause more glare as we see it, that cause us to squint.

If I'm using a film rangefinder I'm not looking thru the lens so am seeing the existing light, not the filtered light coming into the camera (if I have a filter on the lens). But I know I've had to adjust exposure for the different/less/filtered light coming in to the camera. I haven't used a polarizer in awhile since the last time I went to a lake near me I was shooting Polaroids. (And yes, polarizing light technology had something to do with inventing Polaroids but I'd need a refresher on Edwin Land to remember what it was!)

I've used a circular one and it's just like RVT1K described, when you turn it you'll see the effect as you're looking thru the viewfinder and thru the lens. I haven't used one with my digital camera, and don't use one often, just sometimes shooting B&W film (with mechanical not auto film cameras) on sunny days near a lake etc. I don't often use lens hoods either but I can see why you can't when you've got to turn/rotate a circular polarizer.

 

[smoke665]

From what I understand a polarizer blocks? filters? (not sure what describes it best) horizontal rays of light rather than vertical ones, but they actually move at various angles (which is why as you turn the polarizer

Short, concise definition from Hoya USA "Polarized light is light who’s rays have been scattered due to pollution, moisture in the atmosphere and reflection. A circular polarizer filter only allows light rays that are traveling in one direction to enter the lens. The Hoya Circular Polarizers are actually made up of a piece of high quality optical glass followed by a linear polarizing film, this film, which is actually a micro screen, filters out the scatters light rays and only passes light moving in one linear direction. Modern camera meters and auto focus systems can have problems reading light moving linearly is a quarter wave plate is added behind the polarizing film to send the light into the lens in a circular pattern. This circularly polarized light will not interfere with any camera metering or auto focus systems.

Keep in mind that when any kind of light is filtered out, polarized or not, there is a reduction in exposure. That is how the circular polarizer darkens blue skies, it reduces the amount of light coming from the sky into the camera. That is why when a circular polarizer is rotated the shutter speed or aperture will change."