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Subject: "Circular polarizer example with back to the sun" Archived thread - Read only
 
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bclaff</b>donator_silver
Member since 26-Oct-04
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30-Mar-05, 10:28 PM (GMT+2)
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"Circular polarizer example with back to the sun"
 
   Quiet a few knowledgeable posters have stated that sky polarization is non existant or minimal with the sun directly behind the photographer.

This pair of resized but unmodified pictures taken about 15 seconds apart with my back directly to the sun speak for themselves

Bill

Visit me, info and galleries at: Nikon Photos and Information


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  Subject     Author     Message Date     ID  
Circular polarizer example with back to the sun [View All] bclaff</b>donator_silver 30-Mar-05 TOP
  RE: Circular polarizer example with back to the sun briantilleymoderator 30-Mar-05 1
     RE: Circular polarizer example with back to the sun bclaff</b>donator_silver 31-Mar-05 2
  RE: Circular polarizer example with back to the sun dwig 31-Mar-05 3
     RE: Circular polarizer example with back to the sun bclaff</b>donator_silver 31-Mar-05 4
         RE: Circular polarizer example with back to the sun BJNichollsdonator_silver 31-Mar-05 5
         RE: Circular polarizer example with back to the sun dwig 31-Mar-05 6
             RE: Circular polarizer example with back to the sun briantilleymoderator 01-Apr-05 7

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briantilleymoderator
Member since 26-Jan-03
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30-Mar-05, 11:10 PM (GMT+2)
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1. "RE: Circular polarizer example with back to the sun"
In response to message #0
 
  
Thanks for posting this, Bill, it's interesting. Which one is the polarised shot? (just kidding...!)

What focal length and aperture were you using?

Brian
Welsh Nikonian - "exiled" to England

Find out more about me at the:
Nikonians Team pages


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bclaff</b>donator_silver
Member since 26-Oct-04
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31-Mar-05, 00:00 AM (GMT+2)
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2. "RE: Circular polarizer example with back to the sun"
In response to message #1
 
   Brian,

Actually, they are both taken with a polarizing filter!
The left is turned to maximum effect, and the right to minimum effect.

The shooting data is 18-70mm "kit" lens at 18mm f/4 1/800th second.

Bill

Visit me, info and galleries at: Nikon Photos and Information


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dwig
Member since 30-May-04
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31-Mar-05, 01:42 PM (GMT+2)
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3. "RE: Circular polarizer example with back to the sun"
In response to message #0
 
   As your photos show, the phrase "...sky polarization is non existant or minimal with the sun directly behind the photographer" is a misquote of the rule. The correct rule is that sky polarization is non-existant or minimal _in the portions of the sky 180 degress and and 0 degrees from the sun_.

As you can see from the shadows, the sun is not directly behind the camera (its off to the side about 30 degress) and is relatively low to the horizon (long shadows). This means that the portion of the sky behind the upper portions of the monument is closer to 90 degress from the sun than it is 180 degress, hence some noticable polarization effect. You'll note, in the sample pictures, that near the horizon there is little polarization effect as that portion of the sky is much more nearly as 180 degree angle (there's probably some addition aerial haze that is also contributing to the lessened effect).

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dwig
nikonian in paradise (KW, FL)
Current: CP8400, CP950
Retired: F, ELw
Usedto's: F, F2, F3, Nikkormat FTn, 20 f/3.5, 35 f/1.4, 45GN, 55 f/3.5 Micro, 105 f/4 Micro, 300 f/4.5, 180w f/5.6 for 4x5
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bclaff</b>donator_silver
Member since 26-Oct-04
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31-Mar-05, 03:03 PM (GMT+2)
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4. "RE: Circular polarizer example with back to the sun"
In response to message #3
 
   David,

I don't know what protractor you used to get your 30 degree figure. (Remember, I was there.)
Perhaps you can explain why the black footlight in the foreground doesn't seem to have a shadow.

It certainly wasn't "high noon" but at 2:05pm the sun was not particulary low in the sky.

It's certainly true that when we give out our 0, 90, 180 degree advice we disregard that it is a three dimensional problem and that the sun has elevation. Surely, for photographs directly into the sun something stronger than a polarizer is required except at sunrise/sunset when a polarizer would spoil the effect. And photographs with the sun directly behind are quite rare except for those times you are immortalizing your shadow. So 0 and 180 aren't practical cases.

Bottom line: look through the lens and trust what you see. If the polarizer has the desire effect then fine; otherwise take it off (or at least remember that you're losing light for no effect).

Playfully,
Bill

Visit me, info and galleries at: Nikon Photos and Information


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BJNichollsdonator_silver
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31-Mar-05, 10:01 PM (GMT+2)
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5. "RE: Circular polarizer example with back to the sun"
In response to message #4
 
   Isn't that why we put up with the hassles of an SLR viewfinder and the bulk/complexity of SLR bodies?


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dwig
Member since 30-May-04
365 posts
31-Mar-05, 11:46 PM (GMT+2)
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6. "RE: Circular polarizer example with back to the sun"
In response to message #4
 
   Perhaps I'm mis-reading the shadow of the tree that seems to be off to the photographer's right.

Either way both your point about trusting the view through the polarizer (naked eye or through the camera) _and_ my point about the upper portions of the picture not being near the 180 degree point at true.

Depending on where you were, and assuming standard time and not daylight savings time, the sun could have been anywhere between ~25 and nearly 40 degrees from it high point at 2:00pm. From your pictures, its obvious that it was low enough to cast shadows, but high enough and your lens was wide enough that the upper portion of the picture is not near the "180 degress from the sun" position. Had you been shooting more near sunset, the horizon behind the monument would be more nearly 180 from the sun and the sky behind the monument would show less effect although it would still show some if the lens used is as wide as it seems (~24-28mm on film, or the equv on digital)

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dwig
nikonian in paradise (KW, FL)
Current: CP8400, CP950
Retired: F, ELw
Usedto's: F, F2, F3, Nikkormat FTn, 20 f/3.5, 35 f/1.4, 45GN, 55 f/3.5 Micro, 105 f/4 Micro, 300 f/4.5, 180w f/5.6 for 4x5
-----


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briantilleymoderator
Member since 26-Jan-03
2783 posts
01-Apr-05, 10:41 AM (GMT+2)
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7. "RE: Circular polarizer example with back to the sun"
In response to message #6
 
  
I think we're all saying basically the same thing here

The old adage, about polarisers only being really effective with the sun off to the right or left, is a decent rule of thumb but in reality things are more complex. The sun's elevation, as well as the vertical angle of the camera/lens, also influence the effect obtained.

Brian
Welsh Nikonian - "exiled" to England

Find out more about me at the:
Nikonians Team pages


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