How to use the circular polarizing filter.

[Shafique]

I dont understand how the circular movement of the filter ring effects the picture. I see that the contrast changes, but my question is:

1. Does the colour saturation change with the contrast as well..??

2. How is the contrast related to the saturation wrt the circular movement.?

3 Can I have High Contrast Low Saturated pics from this filter ?

4 Can I have High Contrast High Saturated pics from this filter ?

Kindly answer specifically to the point.

Thank you.

[mervlam]

ermmm.. then u need to understand how a circular polariser or even a linear polariser works.

that's university first year level Physics

[Gunjack]

For linear polarising filter, I think they allow certain rays of light to pass through and others not, depending on how u rotate the outer ring. The 2 different glass elements pass/block different rays. Therefore they can allow all the light rays to pass, or some to eleminate glare/reflections... therefore increasing contrast and colour saturation. I hope I am not wrong, heheh!

[Shafique]

Quote: Originally posted by mervlam ermmm.. then u need to understand how a circular polariser or even a linear polariser works. that's university first year level Physics

Mervlam,
Excuse me, my question was on the usage of the circular movement of the polarizer and can be answered without talking about the light semantics going on inside, specially those covered in the First Years Physics...its a question on the application of the filter...on how to use it to get the best saturation and contrast.

Sometimes I dont understand why do people engage in unhelpful and careless replies ...perhaps now you will say I should go back to Primary One to understand human behaviour.

[Shafique]

Quote: Originally posted by Gunjack For linear polarising filter, I think they allow certain rays of light to pass through and others not, depending on how u rotate the outer ring. The 2 different glass elements pass/block different rays. Therefore they can allow all the light rays to pass, or some to eleminate glare/reflections... therefore increasing contrast and colour saturation. I hope I am not wrong, heheh!

Gunjack,
Thanks for your kind reply, I understand that the rotation does filter out certain light element, but I cannot figure out how and which direction of the rotation is for better saturation/contrast.
There may be something I am missing.
Thanks once again anyway for your response.
Cheers,

[Gunjack]

Sorry, I still dun really understand your question... but I'll try again...

For the most effect, make your thumb and pointer finger in a 90 degrees angle like a "gun". Point your thumb to the sun and your pointer finger will point to the level/plane where the polarising filter will have the most effect. Looking through the polarising filter through your lens, rotate the outer ring and look for reflective objects like the clouds, leaves or a puddle of water untill you see the effect you like. The maximum effect is very obvious with the clouds becoming very dramatic and define looking and the water will have no reflection at all and u can see through the water... Polarising filter works most around the afternoon time when the sun is 90 degrees to the land. The contrast will increase together with the colour saturation.

[Shafique]

Quote: Originally posted by Gunjack Sorry, I still dun really understand your question... but I'll try again... For the most effect, make your thumb and pointer finger in a 90 degrees angle like a "gun". Point your thumb to the sun and your pointer finger will point to the level/plane where the polarising filter will have the most effect. Looking through the polarising filter through your lens, rotate the outer ring and look for reflective objects like the clouds, leaves or a puddle of water untill you see the effect you like. The maximum effect is very obvious with the clouds becoming very dramatic and define looking and the water will have no reflection at all and u can see through the water... Polarising filter works most around the afternoon time when the sun is 90 degrees to the land. The contrast will increase together with the colour saturation.

Thanks, as you have mentioned "The contrast will increase together with the colour saturation."..thats the answer I was looking for.
Cheers,

[sulhan]

Hi Shafique.....(assalamualikum)...

For the best effect from polariser, the sun should be at a right angled to the image that you want to take - in all cases try to put the sun at an axis imagining that the sun rises from your left arm ...up above you ...and doen your right arm....(or vice versa).....this will give you the best effect....

Here i have a drawing to illustrate(sorry its a little ugly)




try it out......only your eyes can judge if its the best saturation yo looking for.....


reards,
Sulhan

[andyap]

Hi Sulhan,

Nice and Clear illustration, you are pretty good at this sort of illustration. Good on you.

I am using a circular polarising filter on my Canon SLR.

1) Do you normally have the polarising on all the time like your UV filter?

2) Do you lose a stop when taking picture with the poloriser on all the time?

3) Can I compensate the 1 stop loss via the EV +/- mode?

I like using polarising filter as it really enhance my landscape photography.

Cheers

[mervlam]

Quote: Originally posted by Shafique Mervlam, Excuse me, my question was on the usage of the circular movement of the polarizer and can be answered without talking about the light semantics going on inside, specially those covered in the First Years Physics...its a question on the application of the filter...on how to use it to get the best saturation and contrast. Sometimes I dont understand why do people engage in unhelpful and careless replies ...perhaps now you will say I should go back to Primary One to understand human behaviour.

sorry to make you feel that way. but the basis of how the polariser works is STILL physics. knowing the light semantics can aid to answer those questions. answers will come abt after applying the knowledge of the light semantics.

a linear polariser only allows light waves (essentially EM waves) that oscillates in one direction to pass. the intensity of light cuts down by half after passing thru the polariser (fully polarised) thus with less glare, saturation and contrast improves. light will be most polarised when u rotate the polariser to the angle where objects appear the darkest. this is when intensity of the light is the least.

a circular polariser works the same way except the light is circularly polarised when it passes thru a circular polariser.

the sky is most naturally polarised where the sun is 90 degrees to it. using a polariser here enhances the effect.

the polariser is no "magic" filter as many people perceived. physics can help to explain why and how a polariser works.

Quote: Sometimes I dont understand why do people engage in unhelpful and careless replies ...perhaps now you will say I should go back to Primary One to understand human behaviour.

there's no need to be rude.

[Kit]

Quote: Originally posted by andyap Hi Sulhan, Nice and Clear illustration, you are pretty good at this sort of illustration. Good on you. I am using a circular polarising filter on my Canon SLR. 1) Do you normally have the polarising on all the time like your UV filter? 2) Do you lose a stop when taking picture with the poloriser on all the time? 3) Can I compensate the 1 stop loss via the EV +/- mode? I like using polarising filter as it really enhance my landscape photography. Cheers

No, you don't need a polariser on all the time. Use only when you need it. Another thing to take note when using polarisers is over polarising.

With a polariser, you lose about 1 1/2 stop. Meter the scene without the polariser and take down the exposure and put on the filter and compensate accordingly. However, you might want to try metering the scane with the polariser just to see how the camera's metering system handles the filter.

Some webpages I think could be useful
http://www.photographytips.com/page.cfm/34
http://photographytips.com/page.cfm/304

[mervlam]

Quote: Originally posted by andyap Hi Sulhan, Nice and Clear illustration, you are pretty good at this sort of illustration. Good on you. I am using a circular polarising filter on my Canon SLR. 1) Do you normally have the polarising on all the time like your UV filter? 2) Do you lose a stop when taking picture with the poloriser on all the time? 3) Can I compensate the 1 stop loss via the EV +/- mode? I like using polarising filter as it really enhance my landscape photography. Cheers

1) u do not need to attach a polariser on ur lens all the time. a polariser is a special effects filter. so u should use it whenever u need it.

2) u will lose a stop of light (half the intensity) when using a polariser

3) no need to compensate. ur camera TTL light meter will compensate for u. ie. just use the camera light meter reading and u will get correctly exposed photos

[Shafique]

Quote: Originally posted by sulhan Hi Shafique.....(assalamualikum)... For the best effect from polariser, the sun should be at a right angled to the image that you want to take - in all cases try to put the sun at an axis imagining that the sun rises from your left arm ...up above you ...and doen your right arm....(or vice versa).....this will give you the best effect.... Here i have a drawing to illustrate(sorry its a little ugly) try it out......only your eyes can judge if its the best saturation yo looking for..... reards, Sulhan

Sulhan, Assalmalaikum,
Thanks a million for the concept, it really answers all my questions, and thanks for pulling out the time to draw a wonderful illustration...you are quite an artist and a teacher.

Kind Regards,
Shafique Razzaque.

[sulhan]

Hiee.. Mervlam,


Lets not pump the people here with EM waves and waves theory else we will be ending up having to start a Maxwell's Equation lesson here.

I think, helping the people here understand the use of the polariser should be put in simpler terms as much as possible.

Well...i do have the Popular Photography mag Sept edition....with a rather comprehensive explanation on all l about polariser.

SHould anyone want to have a read...let me know....

FYI: The most efficient angle for photography through the glass to get almost zero reflaction is to be at an agle of about 30 degrees to the glass....

regards,
sulhan

It's always a good idea to check out this web page if you're new to polarising filters: http://www.cliffshade.com/dpfwiw/polarizer.htm

[mervlam]

Quote: FYI: The most efficient angle for photography through the glass to get almost zero reflaction is to be at an agle of about 30 degrees to the glass....

FYI also: It depends on the refractive index of the material.