guide needed on polarizing filter

[Yisehaq]

Hi All,
I just bought my first circular polarizing filter but I couldn't exactly see the effect of it. Therefore, could you explain to me a bit. My questions are

1. I have read that CPL is used to make the sky bluer. Does this also work for overcast day where blue sky is visible or is it just when the day is sunny?

2. On how to use CPL, I have read a thecnique of pointing your finger to the sun and see the direction of your thumb to get the direction of polarization? This seems to make sens when the sun is overhead what about if it's in a certain degree other than 90.
If you can point me to any pictoral tutorial, I would appreciate very much.

Thanks.

[kat]

I just got one a couple days ago too. I'm not to sure how to use it yet but I do know that when I have it on and turn the dial I can see the effects pretty clearly.

Great questions! Looking forward to seeing the answers!

[tirediron]

Congrats! You've just purchased the single most useful photo accessory you will ever own!

When to use it: Pretty much any time you're out doors, especially in bright sun.

What does it do: Reduces reflections and deepns and saturates colours.

How do I use it: You will see the greatest results when the sun is low in the sky, so eary morning, and later afternoon/evening, and when the sun is at 90 degrees to the lens axis, so the thumb analogy is correct.

The CPOL will have little to no effect on the colours and saturation on overcast days, when the sun is high in sky, or when you're shooting toward it/with it at your back. It will still serve to remove reflections from water, glass, shiny metal etc.


This image shows just how deep you can make a blue sky. This was shot early in the morning (7.30am-ish, and with the sun directly on my shoulder

http://www.johnsphotography.ca/Images/Greece/slides/Greece%20(14).jpg


This image shows the effect of a CPOL on water; note that the reflection is almost totally eliminated.

http://www.johnsphotography.ca/Images/Greece/slides/Greece%20(13).jpg

Hope that helps.

[Marko]

Thanks so much for that terse explanation and the examples T.I. :highfive:

[kurtdriver]

Would a linear polarizer be used any differently? My Mamiya RB67 came with one that's presumably as old as the camera eg. early 70's and came with a linear polarizer.

[Yisehaq]

Thanks TI, that was helpful.


Just to clarrify some points. Sorry for forgetting my geometry :wall-an: but doesn't 90 degrees to the lens axis mean that the sun is directly on the head?

Will it be effective to use it to remove some glare from a car window at noon?

[tirediron]

Would a linear polarizer be used any differently? My Mamiya RB67 came with one that's presumably as old as the camera eg. early 70's and came with a linear polarizer.

The effects will be visually identical (or nearly so). It's just that some modern auto-focus systems don't play nicely with LPOLs, so pretty much everyone has switched to CPOLs.

[tirediron]

Thanks TI, that was helpful.


Just to clarrify some points. Sorry for forgetting my geometry :wall-an: but doesn't 90 degrees to the lens axis mean that the sun is directly on the head?

Will it be effective to use it to remove some glare from a car window at noon?

That would be 90 degrees as well, however I mean 90 degrees when viewed from overhead. The CPOL will still help to remove reflections at high noon, but the effect may not be as strong as desired.

Just remember that the best conditions happen when the sun is close to the horizon and coming from the direction of your shoulder when you're pointing the camera at the subject.

[kurtdriver]

Thank you T.I. I understand the linear polarizers mess up autofocus which is why they don't really work well with cameras having that feature.

[EJC]

In addition to Tiredirons tips here is a trick I use.

Shape your hand into a pistol with your thumb and index finger at 90 degrees. Point the index finger at your subject.
Face the palm of your hand to the sun as if you're going to catch it.
Your thumb will point in the direction the idex mark on your CPOL should be pointing.

Practice on easy subjects,
Blue sky with puffy clouds watch the sky go from watery blue to deep blue
Clear water with a rocky bottom the water will go from reflecting the shiny sky to clearly showing the bottom,
A building with lots of windows acts much the same as water

When you get results with those try a bush with shiny leaves. Turning your filter you will see the leaves go from boring flat and shiny to bold and richer tones. Then try less reflective surfaces and look for subtle changes.

I hope this helps

cheers

[Yisehaq]

Thanks T.I. and EJC, that was helpful.

[jabber]

I don't know if anyone mentioned yet that you will lose a stop due to the diminished light coming through the lens. Great examples, tirediron.

[kkjensen]

IMHO I've always made a circular polarizer the 1st filter I buy after a UV to protect the lens from dust and damage. While untrained with them they do help out a lot and on some vacations I've just left it on the lens for the duration of most sunny days.

One thing to remember about them is they rotate! :) "no, really?!?" I only say this because the kit lenses that come with most cameras do not have an internally focus mechanism so the polarizer will get rotated out of alignment anytime the camera focuses on something, making it a bit hard to capture a moving subject and get the full effect of the filter. I try to take two shots, one to get the camera focused and as insurance that I don't completely miss the moment and then (since the lens won't rotate too much if the focus point stays the same) again once I've taken a second to dial in the cp for the effect I prefer.

[jhuang999]

If i have both the polarizer and UV lens, what order should they go onto the lens? Thanks!

[Mad Aussie]

If i have both the polarizer and UV lens, what order should they go onto the lens? Thanks!
If it's a Circular Polarizer you need to be able to turn it so I'd be putting it on last.
Generally speaking, the UV/Skylight filter goes on first and stays there.

[Andrew]

I put my UV filter on last and only to protect the polarizer. With a polarizer I dont think you need a UV filter for any other reason. UV only cuts the blueish haze from dense water vapours (lakes, ocean, altitude, long distance landscape shots) which the polarizer should eliminate most of anyway.

http://www.photography.ca/Forums/f7/uv-filters-digital-cameras-13134.html

[Mad Aussie]

Actually I think UV's do very little if anything at all other than provide something to scrath other than lense front element. As a UV filter (protecting the camera's sensor from UV rays) it's useless as all camera sensors have a UV filter directly over them these days.

[Iguanasan]

I wasn't going to say anything in this thread at first but this is one of those habits that I really don't understand. Why anyone would put a $20 filter on a $300, $800, or $1500+ lens? If all you are trying to do is protect the lens from bumps then I would suggest a lens hood. It should protect the lens from any bumps and drops without getting in between your lens and the subject. The less that comes between the sensor and the subject the better.

[Peter]

This was so helpfull guys. Thanks

[Mad Aussie]

I wasn't going to say anything in this thread at first but this is one of those habits that I really don't understand. Why anyone would put a $20 filter on a $300, $800, or $1500+ lens? If all you are trying to do is protect the lens from bumps then I would suggest a lens hood. It should protect the lens from any bumps and drops without getting in between your lens and the subject. The less that comes between the sensor and the subject the better.

Not always Iggy .... have a look at the lens hoods on wide angle lenses. The hood on my 10-22mm wouldn't help much at all. Mind you ... I usually don't use any filters at all on my wide angle due to the vignetting you get if you stack them and they can add to lens flare etc in certain lights ... like night time.

[Marko]

I see your logic iggy and i don't discount it one bit....If money were not an object, i would never ever use a UV filter.
Personally - the ONLY reason I have a UV filter on the lens is to protect it so that it has a higher resale value.

Lens hoods are good but they can be a pain in the butt to put on and take off and they still leave the glass on the lens vulnerable to accidental scratches etc.

Personally - I often REMOVE the UV filter when i use the polarizing filter due to vignetting issues on ANY lens, not just wide angle.

I should say that I have not done tests to see if there is any noticeable loss in quality with/without UV lens, but the tests I have read suggest that the quality is negligible with a good UV filter. The UV filters I use are either Nikon or BW and they are closer to 70-80 dollars each.