polarising filters on my Canon EOS 600D

[stu123]

I recently bought a digital circular polarizing filter for my camera, as i had seen photos showing the benefits of using polarizing filters and thought i would give it a go. So far i'm unimpressed and am wondering if there are any tricks or tips regarding how to get the best out of the filter.

[chrisk]

maybe post some samples. are you rotating the filter to get the polarisation ? what time of day etc etc etc

[stu123]

yeah i rotated the filter, but i didnt really notice any major difference. I tested the filter at around 2-3pm this afternoon, a bit cloudy but mostly sunny

[Remorhaz]

The polarisation works best when the camera is pointed 90 degrees to the sun - so for example pointing directly towards the sun or away results in no change no matter where you rotate the ring to.

[biggerry]

There are plenty of sources on the net regarding how a CPL works, some quite interesting reads too.

However Rodney has covered teh crux of it, the maximum effect is at 90 degrees to the position of the sun.

How about trying it on some water reflections, or try pointing it at some green leaves (at 90 to the sun) and see how the reflections are removed and consequently the saturation increased.

http://en.wikipedia.org/wiki/Photographic_filter#Polarizer

http://en.wikipedia.org/wiki/Polarizer

[surenj]

yeah i rotated the filter

Perhaps try standing 90 degrees to the sun to get the maximum effect... Mainly watch the blue sky and the definition of clouds as the effect is easily noticed.

[Mr Darcy]

I posted a series of photos exploring the effect of polarisers on the sky a few years ago. I just checked & they are gone from the server. I'll see if I can dig them out and post them here.

But as already noted, the effect is very variable depending on where you are pointing relative to the sun. as it depends on the degree of polarisation in the sky. It also depends on where the sun is in the sky. YOu will get greatest effect early (or late in the day in mid winter while you are pointing the camera due south. As you deviate from this the effect will get less.

[stu123]

i actually just found a tree with the sun reflecting of the leaves, and i worked out how to use the filter, and i saw the effect. Made a big difference, just had to try it under the right conditions i guess. Thanks for the advice though.

[PiroStitch]

Another useful experiment is to try taking a photo of a store window or car window. A CPL will help cancel out the reflections you see in the window.

[gstark]

Or the sunlight reflecting off the water on a large expanse of water, like a beach or harbour scene.

[Mr Darcy]

I tracked down my set of test photos using a polariser. This one says it all...


CPLTestUW
CPL test at 10mm. Camera pointed North (southern Hemisphere). Sun low in the west. You can see how the effect varies with the angle to the sun. And for that matter why you shouldn't use a polariser with an Ultrawide

[lightning]

I have seen an ad for an adjustable ND filter which I think says that they use polarised glass (?) to create the adjustable ND effect, so would that mean that a normal polarising filter used incorrectly, would effectively be an ND filter?

[lightning]

Just having a play with polariser (totally non scientific!) by the light meter on my d80, darkest setting 2 stops over, lightest setting 1 stop over, no filter at all 1 stop under.

[Mr Darcy]

I have seen an ad for an adjustable ND filter which I think says that they use polarised glass (?) to create the adjustable ND effect, so would that mean that a normal polarising filter used incorrectly, would effectively be an ND filter?

Yes there are a few around. If you set two polarisers at right angles to one another (glass in the same plane but mark at 90 degrees) you will block pretty much all light getting through. varying the angle will progressively reduce the effect. This is called crossing the polarisers. Linear polarisers work better for this. A single polariser is effectively an ND filter, usually about 2X though the effect varies by brand. For just this reason I often use one for waterfalls when travelling light. It slows the shutter speed just enough though you won't get the full dream effect.

Another neat trick is to place one POL on your light source and another on your camera. This will give you pretty much full control over specular highlights. as direct reflections are still polarised and can be eliminated by "crossing" the polarisers while the scattered light has lost its polarisation and will get through to the sensor. Also if the subject is translucent it will often twist the polarisation differently for different wavelengths to give you interesting false colours This is used extensively in geology for mineral identification and stress testing in the glass and plastics industries.