roy_rogers Posted June 19, 2007 Share Posted June 19, 2007 I have a hoya circular polariser, it has a white mark on it for reference of where it was. Now I keep reading they work best at 90 degree angle to the sun, forgive me if Im being stupid but I just dont understand this. Does this mean the line has to line up with the sun at a 90 degree angle or the cameras position? Ive read about it but I just dont understand what is meant by the 90 degree or at least its confused me to how you can get a 90 degree angle when the sun, does this mean if the sun is say high in the north east, then the line has to be 90 degrees right? Im confused. Do you even need to know the angle? Cant you just move the filter around at look what does the effect best? thanks Link to comment Share on other sites More sharing options...
don_cooper Posted June 19, 2007 Share Posted June 19, 2007 You're right, just turn it and see the result. The 90 degree angle refers to the angle where the effect will most dramatic. If you point it directly away from the sun (180) hardly any effect will be noticed. Link to comment Share on other sites More sharing options...
mcara Posted June 19, 2007 Share Posted June 19, 2007 Wouldn't 180 degrees away from the sun be below the horizon (unless the observer is standing on Everest)? Link to comment Share on other sites More sharing options...
gary evans Posted June 19, 2007 Share Posted June 19, 2007 Mihai, I don't think Don was being literal like you are reading it. Basically, if the sunlight is coming from due south, 180 degrees away would be due north. Link to comment Share on other sites More sharing options...
alan_olander1664878205 Posted June 19, 2007 Share Posted June 19, 2007 Point your index finger at the sun and extend your thumb up at 90 degrees. Anywhere your thumb can point, by rotating your hand, while still aimed at the sun will be 90 degrees to the sun and polarization will be at its maximum. 180 degree away would be if you pointed the camera at a scene with your back to the sun. Link to comment Share on other sites More sharing options...
alan_olander1664878205 Posted June 19, 2007 Share Posted June 19, 2007 Check this out: http://luminous-landscape.com/tutorials/polarizers.shtml Link to comment Share on other sites More sharing options...
Ed_Ingold Posted June 19, 2007 Share Posted June 19, 2007 "Now I keep reading they work best at 90 degree angle to the sun..." The sky is polarized most strongly in a band centered at 90 degrees to the sun. A polarizer will have the greatest darkening effect in this region. Whether darker is always "better" is questionable. Light from any non-metallic surface tends to be polarized. Therefore a polarizing filter can remove reflections from water, glass, foliage and rocks, increasing the color saturation of the latter. This is arguably the best use of a polarizer. Link to comment Share on other sites More sharing options...
hjoseph7 Posted June 19, 2007 Share Posted June 19, 2007 Forget about all this 'degree' geometry stuff. Most of us failed geometry for christ sakes. Just turn the dial until the white mark is about 1/4 of the way down clockwise. Make sure that the Sun is at your side not infront or back of the scene you are trying to take. If 1/4 turn doesn't work, turn it clockwise another 1/4 turn until the white mark is at the half-way point. Good Luck ! Link to comment Share on other sites More sharing options...
rjacksonphoto Posted June 19, 2007 Share Posted June 19, 2007 Better yet, if you're using an SLR, just ignore the white mark and turn it until it has the effect you want. Then press the shutter release. Voila! Link to comment Share on other sites More sharing options...
frank_skomial Posted June 20, 2007 Share Posted June 20, 2007 Your camera does not know about any filter on the lens, but you do. Auto white balance, if your camera has it, could add own interpretation. Using manual white balance could give you more predictable results. You just need to try what works best for your expectations. Link to comment Share on other sites More sharing options...
alec_myers Posted June 20, 2007 Share Posted June 20, 2007 "Light from any non-metallic surface tends to be polarized." If I remember my physics properly, light reflected off metals and other specular reflections are polarized to some extent; diffuse reflections off non-metals are not. Link to comment Share on other sites More sharing options...
zackojones Posted June 20, 2007 Share Posted June 20, 2007 One little tip for using polarizing filters - if you have sunglasses on you might not get the results you're expecting. Try looking through the viewfinder without you sunglasses. I accidentally screwed up a few photographs because of this. Link to comment Share on other sites More sharing options...
dgfassett Posted June 20, 2007 Share Posted June 20, 2007 We have been here before. Light directly from the sun is considered a point light source, that is, it consists of light rays alligned in parallel. When these rays strike almost any object, they become diffused. The polarizer, any polarizer, is designed to pass only those light rays in a parallel allingment and reject those that have become diffused. This then, eliminates the diffusion that not only will reduce the clairity of the recorded image, but will also allow stray diffused rays to bounce around within a lens. Because of a lens auto focus system, the filtering of some of the light may diminish the ability of the lens to focus. The circular polarizer overcomes this shortcoming. Link to comment Share on other sites More sharing options...
brucecyr Posted June 21, 2007 Share Posted June 21, 2007 "Because of a lens auto focus system, the filtering of some of the light may diminish the ability of the lens to focus. The circular polarizer overcomes this shortcoming." I should think the maximal 2 2/3 stops of light loss from polarizer use would greatly exceed the diffusion effect of unpolarized light -- would it not? Link to comment Share on other sites More sharing options...
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