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Author Topic: Help Understanding Vignetting With a Circular Polarizer  (Read 1285 times)

mpower

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Help Understanding Vignetting With a Circular Polarizer
« on: June 05, 2017, 08:47:46 pm »

Hi all, I've attached a landscape shot from Peru by me. I am here to ask specifically why it has so much vignetting.

Equipment: Nikon F5; Nikkor 20mm f2.8 (non-D); Kodak Ektar E100VS (freezer kept); Amazon Basics MC Circular Polaizer (turned to max effect).

I've tried it out back at home (with a lamp, lol) and yes, the CP definitely causes the vig seen in the photo when mounted on that lens.

My question is, would a better-grade CP (such as Nikon) have less or no vignetting? Or is it something that happens because of using a CP on a 20mm wide?

Thanks all,

Matt
« Last Edit: June 05, 2017, 08:59:00 pm by mpower »
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Alan Klein

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #1 on: June 05, 2017, 10:02:03 pm »

The polarizing is most with light at a 90 degree angle to the sun.  So what happens, it's darkest at 90 degrees and lightens as you move away from the 90 degree angle.  Rotating the filter will lessen the polarizing effect as well as the gradient effect. (you'll notice that saturation decreases and increases as does elimination of the reflections off of foliage.  It's not just the sky that is effected.)

Also, you'll see the most  gradient with wide angle lenses because you are shooting so much of the sky.  With zoom lenses, the effect won't be as noticeable because your angle of view is much smaller so the gradient is less for any smaller portion of the sky.

The manufacturer of polarizing filter has no effect as far as the problem you are describing.  Good luck.

Alan Klein

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #2 on: June 05, 2017, 10:06:12 pm »

In reviewing your photo.,it seems like the sun is behind you.  So the darkest part of the sky is around 90 degrees to the sun. That shows at the top of your photo.  The sky gets lighter as it moves towards the horizon because the angle is increasing from 90 degree max to around 180 degree minimum polarizing effect.  I hope this all makes sense.

Alan Klein

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #3 on: June 05, 2017, 10:09:01 pm »

What I try to do is watch the effect as I rotate the filter.  You may often find that maximum polarizing is too much.  That a lighter approach provides a nicer picture without the effect being too noticeable to the viewer.  It's sort of like adding salt to your food. You don't want to overdo it. Just enough to bring out the food's natural flavor. 

mpower

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #4 on: June 05, 2017, 10:14:49 pm »

Alan, yes the sun was mostly behind me. Your posts are very informative (I'm returning to Peru in two months) and If I think I've got your advice right, it might be, "Don't turn it up to 11 for every shot!"
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Alan Klein

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #5 on: June 05, 2017, 10:40:48 pm »

I glad I could help. 

francois

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Re: Help Understanding Vignetting With a Circular Polarizer
« Reply #6 on: June 06, 2017, 08:59:43 am »

There's a short article here on Luminous Landscape about polarizers: https://luminous-landscape.com/polarizers/
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Francois
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