How to use a Circular polariser

ziggy©

ziggy©

Messages
1,939
Name
Dini
Edit My Images
Yes
I am thinking about getting a circular polariser for my Canon 15-85mm lens.
Usually (without a polariser) when i want to get an image with the most pop, i try to make sure that the sun is always behind me. This usually gives me a pretty good exposure with nothing blown out etc.

I have been reading about how to use a circular polariser and i found that for maximum effect, the sun has to be either on my left or right? Is this correct? If so, why?

Additionally,
- What happens when you rotate the polariser. Does this just increase/decrease the effect?
- Is a circular polariser a filter that can be kept on the lens continously or do i have to remove it when im not using it? And can it go on top of the UV filter?
- Is there a situation where the polariser will actually produce worse result compared to when the filter is not used?

Ta
 
polarizer works by allowing light through that is oriented in a specific orientation. Light moves in waves, both up and down and left and right. Scattered light (which is what we see) is coming from all orientations. A polarizer filter is made up of super tiny slits that the eye can't see, but that only allow light traveling in the same path as the slit to pass through. The two different rings have the slits running in slightly different directions. In a linear polarizer, there would be no light that gets through if the slits were 90 degrees opposite to each other. A circular polariser is more complicated geometrically, but the same general principle applies.

You'll see the most effect in the sky at 90 degrees to the sun. From water and plant surfaces the sun doesn't matter as much, it is the angle to the surface that is reflecting.

You could leave a polarizer on all the time, but you're going to loose 2 stops or more of light.

I wouldn't use one with a UV filter. Been there, done that. You'll lock them together if you're not careful and they are a pain to get back apart. If it is for a quick one off, then fine. Just be careful. If you're using a polarizer all day, then loose the UV.

Thanks
Rick
 
I have just started using a polariser - few weeks now... (hmmm... I thought mine was a UV one too) :thinking:

I tell ya, blooming marvellous - you can pop the clouds and scenes, slow down the shutter speed... but the best, best, BEST thing of all is being able to see thru water - it's just fabulous - if you get to just the right spot - you can take the shine completely off the water and what a difference :clap:

Last weekend we were shooting at the beach and did a comparison of cameras (thinking mine is over exposing - grrr) - anyhoo, we shot a big 'ole rock on the beach - the first one was a very shiny rock and on turning the polariser it became a flat/matt rock... so much better.

Personally, I can't imagine (other shooting macro or indoors) shooting without them now and wonder how I ever shot without them. So far it has not been removed from my lenses ;)

One thing I did notice and still don't know why... there is a black spot in some lighting - I took a lot of photos of some engine houses (mines) on the moors - beautiful blue skies - and my shots have a dark contrast on most of them :shrug: Not sure what I was doing wrong or what caused the very dark shots (almost like half a vignette on either the left or right)

Will look forward to reading what others have to say. :)
 
Another probably dozy question - I'm away in June and have a scene I'd like to try to add star trails to, but it points due south. With Polaris behind me, will I get anything worth mentioning? What about pointing south-east (ish)?
 
Lol why would anyone want or need to put a cpl over a uv filter?!

Uv filters have no effect on digital so can only serve as protection filters at best (worst, degrade iq but that's been covered well already!). Stack them and you'll only increase the chance of Vignetting and the higher chance you'll degrade iq.

And with a cpl on, if you only use the uv for protection, which it's only use actually is, you have a cpl protecting the lens anyway.

Ooooo, glad I got that off my chest!
 
Last edited:
just turn the ring until you reach the effect that it. For an optimal result the light should come perpendicular to the lens
 
CPLs are useful for cutting out reflections from glass, metal and water and the effect is much the same as wearing polarising sunglasses. They can also improve the colour of green vegetation, and darken blue sky to emphasise the clouds. We used to use yellow and orange filters with B & W film for the same purpose.

I wouldn't leave it on all the time. You will lose 1 or 2 stops of light, and CPLs should be used selectively, when they will improve the image. They're not a short cut to better photographs.
 
MartynK said:
CPLs are useful for cutting out reflections from glass, metal and water and the effect is much the same as wearing polarising sunglasses. They can also improve the colour of green vegetation, and darken blue sky to emphasise the clouds. We used to use yellow and orange filters with B & W film for the same purpose.

I wouldn't leave it on all the time. You will lose 1 or 2 stops of light, and CPLs should be used selectively, when they will improve the image. They're not a short cut to better photographs.
Click to expand...

Good points apart from cutting out reflections from metal, they do not do that unfortunately.
 
casts_by_fly said:
polarizer works by allowing light through that is oriented in a specific orientation. Light moves in waves, both up and down and left and right. Scattered light (which is what we see) is coming from all orientations. A polarizer filter is made up of super tiny slits that the eye can't see, but that only allow light traveling in the same path as the slit to pass through. The two different rings have the slits running in slightly different directions. In a linear polarizer, there would be no light that gets through if the slits were 90 degrees opposite to each other. A circular polariser is more complicated geometrically, but the same general principle applies. You'll see the most effect in the sky at 90 degrees to the sun. From water and plant surfaces the sun doesn't matter as much, it is the angle to the surface that is reflecting.

You could leave a polarizer on all the time, but you're going to loose 2 stops or more of light.

I wouldn't use one with a UV filter. Been there, done that. You'll lock them together if you're not careful and they are a pain to get back apart. If it is for a quick one off, then fine. Just be careful. If you're using a polarizer all day, then loose the UV.

Thanks
Rick
Click to expand...

Sorry, but what I have highlighted is a load of rubbish. One ring is just a carrier to allow you to rotate the filter.

Only if you used 2 linear polorising or 2 circular polorising filters together. That is how variable graduated filters are made.

Do not use a linear polorising filter on a modern DSLR as it will completely cock up the metering and AF.
 
With a CPL, if you had one attached and you were shooting motorsport, would this have a negative effect on the AISERVO focussing system? ie make the focussing less reliable, even though you have reduced the glare on the car?

Hope that makes some sense.
 
clariasync said:
With a CPL, if you had one attached and you were shooting motorsport, would this have a negative effect on the AISERVO focussing system? ie make the focussing less reliable, even though you have reduced the glare on the car?

Hope that makes some sense.
Click to expand...

Not if you use a CPL as opposed to a linear version.

The big issue you may find is the loss of 2 stops of light. This may be counteracted by raising the ISO, opening the aperture or decreasing the shutter speed, although depending on circumstances none of these may be possible.
 
EdBray said:
Not if you use a CPL as opposed to a linear version.

The big issue you may find is the loss of 2 stops of light. This may be counteracted by raising the ISO, opening the aperture or decreasing the shutter speed, although depending on circumstances none of these may be possible.
Click to expand...


Thanks for that Ed. How do you distinguish between the two?

Thanks
 
clariasync said:
Thanks for that Ed. How do you distinguish between the two?

Thanks
Click to expand...

Physically you can't, it is more about how they polorise the light than how they look. A circular poloriser will be marker as such or as a CPL,
 
EdBray said:
Physically you can't, it is more about how they polorise the light than how they look. A circular poloriser will be marker as such or as a CPL,
Click to expand...

I see. Do you think there is a marked difference in performance of CPL's based on their price differences?

Sorry if that is a silly question.

Thanks
 
clariasync said:
I see. Do you think there is a marked difference in performance of CPL's based on their price differences?

Sorry if that is a silly question.

Thanks
Click to expand...

The polarising performance between various filters is pretty similar TBH, but low grade polarising foils affect sharpness, particularly on longer lenses (which magnify imperfections).

The filter you want is a Hoya HD CPL, which is not only very high quality, but only reduces the overall exposure by 1.2 stops. I use one a lot, and hardly notice it's there - apart from the dramtic effect it can have. Very effective for cutting reflections off the windscreen so you can see the driver (y)

Amazon usually the best bet.
 
HoppyUK said:
The polarising performance between various filters is pretty similar TBH, but low grade polarising foils affect sharpness, particularly on longer lenses (which magnify imperfections).

The filter you want is a Hoya HD CPL, which is not only very high quality, but only reduces the overall exposure by 1.2 stops. I use one a lot, and hardly notice it's there - apart from the dramtic effect it can have. Very effective for cutting reflections off the windscreen so you can see the driver (y)

Amazon usually the best bet.
Click to expand...

Thanks for that Hoppy. What sort of price can one expect to pay for one of these?

Thanks
 
clariasync said:
Thanks for that Hoppy. What sort of price can one expect to pay for one of these?

Thanks
Click to expand...

Check Amazon. £50-£80ish depending on the size. They're top of the Hoya range so not the cheapest, but there are more expensive brands.
 
String said:
One tip with filters. Sharpen a 2B pencil and run the tip of the pencil in the grooves of the thread. Graphite is a good lubricant and helps to stop filters jamming on each other...
Click to expand...

Vaseline also works rather well I've found. :)
 
Another tip which I learnt the expensive way at the weekend :bonk:- when rotating the polariser, always rotate it the same direction as fitting the filter - that way, if it's not on tight enough, and you are over the top of water when using it............:bang:

I won't forget that once I've bought a replacement :wacky:
 
RB Simon said:
Another tip which I learnt the expensive way at the weekend :bonk:- when rotating the polariser, always rotate it the same direction as fitting the filter - that way, if it's not on tight enough, and you are over the top of water when using it............:bang:

I won't forget that once I've bought a replacement :wacky:
Click to expand...

I lost a 10 stop Hitech into the North Sea having shot one frame with it. :bang:
 
Edward - please do not tel my Hoya LPL that it is not supposed to work on my DSLR. ;)

I think that some LPLs (especially cheap ones) may cause some problems but I do not get many. No focusing issues, but occasionally it throws the exposure off a little.

I have a cheap CPL (which I got by accident :bonk:) which causes much more trouble.
 
Oggy said:
Edward - please do not tel my Hoya LPL that it is not supposed to work on my DSLR. ;)

I think that some LPLs (especially cheap ones) may cause some problems but I do not get many. No focusing issues, but occasionally it throws the exposure off a little.

I have a cheap CPL (which I got by accident :bonk:) which causes much more trouble.
Click to expand...

That's my experience too. Linear polariser affects exposure metering unpredictably, though not massively, but AF seems okay on my Canons. However, I think different cameras vary.

TBH though, I don't see the point of not getting a circular polariser. They work exactly the same, and linears are generally special order only these days.
 
Last edited:
Although I only have limited experience of the circular polariser, it is good for two things:

Cutting out some reflections.
Varying the colour of the sky/clouds.
 
String said:
One tip with filters. Sharpen a 2B pencil and run the tip of the pencil in the grooves of the thread. Graphite is a good lubricant and helps to stop filters jamming on each other...
Click to expand...

That's a brilliant tip, thanks Dave.(y)
 
casts_by_fly said:
polarizer works by allowing light through that is oriented in a specific orientation. Light moves in waves, both up and down and left and right. Scattered light (which is what we see) is coming from all orientations. A polarizer filter is made up of super tiny slits that the eye can't see, but that only allow light traveling in the same path as the slit to pass through. The two different rings have the slits running in slightly different directions. In a linear polarizer, there would be no light that gets through if the slits were 90 degrees opposite to each other. A circular polariser is more complicated geometrically, but the same general principle applies.

You'll see the most effect in the sky at 90 degrees to the sun. From water and plant surfaces the sun doesn't matter as much, it is the angle to the surface that is reflecting.

You could leave a polarizer on all the time, but you're going to loose 2 stops or more of light.

I wouldn't use one with a UV filter. Been there, done that. You'll lock them together if you're not careful and they are a pain to get back apart. If it is for a quick one off, then fine. Just be careful. If you're using a polarizer all day, then loose the UV.

Thanks
Rick
Click to expand...

question from a dumbo.......what's the best thing to do to compensate for the loss of light?
 
extremenovice said:
question from a dumbo.......what's the best thing to do to compensate for the loss of light?
Click to expand...

You just have to increase the exposure, as you would if a cloud comes over. Same difference. The camera's exposure meter will compensate automatically.

It's not quite as high as two stops though usually - the darkest I have tried is 1.9 stops and most are around 1.6-1.8 stops and that's not usually a problem in the kind of situation you tend to use them in, ie bright blue skies, landscapes etc.

Or you can use one of the lighter-tones versions around, like the Hoya HD, which is only 1.2 stops. It's the one I use, best you can get IMHO. Hardly know it's there :)
 
A linear pol may cause problems with AF cameras as it polarises from both sides, incident and reflected. But not always. It is actually a better polarisation than circular. Circular polariser is just linear with a quarter wave retarder stuck to the rear. This allows the filter to to polarise through one side. Left and right handed versions are available, but left is used more. If you have a filter and are unsure whether it is Linear or circular, hold something silver, a coin etc against it. If if goes black on one side it circular. If it stays silver it's linear.
Dean.
 
Dino f said:
A linear pol may cause problems with AF cameras as it polarises from both sides, incident and reflected. But not always. It is actually a better polarisation than circular. Circular polariser is just linear with a quarter wave retarder stuck to the rear. This allows the filter to to polarise through one side. Left and right handed versions are available, but left is used more. If you have a filter and are unsure whether it is Linear or circular, hold something silver, a coin etc against it. If if goes black on one side it circular. If it stays silver it's linear.
Dean.
Click to expand...

Sorry, but none of this makes any sense at all.
 
You must log in or register to reply here.
Back
Top