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Old Mar 31, 2006, 7:31 PM   #1
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OK this has to be real newbie questionbut I gotta start somewhere. I went to a short airshow today to try out shooting some planes and a USAF F16 doing a demo. I bought a circular polarizer to use and try out too. I am using a Canon 20D with a Canon 70-300 Image Stabilizer 1:4-5.6 IS USM lens.

I tried different shooting settings on the camera from the sports mode to TV shutter prioity with a shutter speed from 1000-2500 and a ISO of 100 and 200. I was on my boat rocking around which made this even more difficult. I will be on land Saturday and Sunday shooting more of the Air Show and the Indy Car race in St. Petersburg FL.

So, with that back ground what do I do with the polarizer filter? It turns but I do not know were it should be set at when I turn it. Alot of my pictures of the planes in the skyturned out too dark which I believe to be too fast of a shutter speed but all of the seem kinda of dull and not in great focus. I was hpoing to use the polarizer filter to get that deep dark blue sky in my plane photo's.


This shot was fixed the best I could in PS 2
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Old Mar 31, 2006, 7:38 PM   #2
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Another from today fixed but it still is horrible.
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Old Mar 31, 2006, 7:41 PM   #3
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I shot this yesterday in my backyard. It is a KC135 Tanker based at MacDill AFB.
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Old Mar 31, 2006, 7:58 PM   #4
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The filter acts as a 1.5 X
neutral density filter at its minimum polarization and 2X at its
maximum. For darkening a blue sky, the maximum effect occurs
in a clear sky at right angles (90 degrees) to the light emanating
from the sun.
To use a polarizer for maximum effect, a simple rule of thumb
(literally) is to point your thumb at the sun, then extend your
forefinger (like your making a handgun). Maximum polarization
occurs at the direction your forefinger is pointing. When it comes
to reflections, the polarizing filter works best on light that passes
through the filter at an optimal angle (say 30 or 40 degrees)
from the reflecting surface. If you want to achieve maximum
polarization, you would do best to choose your subject, then
determine the viewpoint needed to achieve 90° (30°/40° for
reflections).

Here's a tutorial that you might find interesting: http://www.luminous-landscape.com/tu...larizers.shtml

The effect on your skies is going to depend a lot on the time of day when you shoot and where the plane is relative to the sun when you shoot. Don't know why the pix you took turned out generally too dark. The camera should compensate for the filter by just giving more exposure than it otherwise would.

I used to live in St. Pete a couple miles as the crow flies from downtown where they have the St. Pete Grande Prix and I could hear it plain as day. There's always some problem with the event but they bring it back every year. Probably just because it's something Tampa doesn't have -- and might get if St. Pete nixed it.

Have fun!

Grant
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Old Mar 31, 2006, 8:08 PM   #5
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thanks Grant! I guess trying to use a circular polarizer with jet flying around the sky at 700+mph is going to be pretty much impossible.

I noticed when I turned the polarized it got dark then light again. Should it be dark or light or in between?
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Old Mar 31, 2006, 8:18 PM   #6
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mdrums wrote:
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thanks Grant! I guess trying to use a circular polarizer with jet flying around the sky at 700+mph is going to be pretty much impossible.

I noticed when I turned the polarized it got dark then light again. Should it be dark or light or in between?
A polarizer only works with certain angles of light, so trying to use one on a target moving across the sky will not produce very effective (consistent) results. The best tip to remember is this: Hold your hand like you're forming a "gun": forefinger out and thumb pointing up. Point your forefinger at the sun, then with the forefinger as "axis" rotate your hand. The curve described by your thumb is the direction where polarization effects will be strongest. Shooting directly towards or away from the sun will minimize polarization effects.

As to whether the photo "should" be dark or light--that's a question for you to answer. The point of the polarizer is to change the photograph to make it appear more attractive to you.
The polarizer can produce some dramatic dark blue skies with puffy clouds when set to its max "dark" setting, and there it also acts as a nd filter, cutting off sharp highlights on grass and other organic surfaces. But is that the result you are looking for? There's no "right" answer. Experiment and find what results you like best.

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Old Mar 31, 2006, 9:52 PM   #7
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The front element on your lens rotates as the lens focuses. This means that the polariser rotates too, and this changes the polarisation. To use one with a rotating lens you basically have to pre-focus manually and set the desired level of polarisation before taking the shot. This is not easy to do with moving subjects and is why virtually no quality lenses have rotating front elements.
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Old Mar 31, 2006, 10:56 PM   #8
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Thanks. I had very similar questions. Just realized when I first used my Linear Polarizer on my Minolta Maxxum 5D that the lens would focus and throw off the axis of the polarizer, which can be a pain, especially in action shots.

By the way, is the focusing or the exposure supposed to be thrown of by the linear polarizer, or both? It seemed to work fine the couple of times I tried it.

My other question is this: Are the markings or notches on the polarizer supposed to line up with the angle ofthe sunlight or are theydelineating the axis at which the polarization is strongest, meaning the markings should be lined up at 90 degree angle to the sun.

Thank you.

Rainer

http://euromaninla.zoto.com/galleries


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Old Apr 1, 2006, 12:46 AM   #9
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Quote:
My other question is this: Are the markings or notches on the polarizer supposed to line up with the angle of the sunlight or are they delineating the axis at which the polarization is strongest, meaning the markings should be lined up at 90 degree angle to the sun.
I'm new to DSLR so this question might not make sense, why are you using a linear polarizer? I thought for dSLR you have to use circular polarizer, otherwise metering and focusing gets all messed up?


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Old Apr 1, 2006, 8:11 AM   #10
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Linear polarizers only affect some through the lens auto focus systems, not metering sytems. I have an old one that works very well with my Pentax *ist DS and a 50 mm 1.7 lens, a manual focus lens.

When I was first asking about a polarizer, someone told me to have the sun off my shoulder for getting maximum effect. That works out to the same 90 degrees from the sun, but is easier for me to use that as a quick reference when I'm actually taking pictures.
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