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DJI. Polarising effect of P4P filter.
1096 12 2017-2-15
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liningiv
Second Officer
Flight distance : 329409 ft
United Kingdom
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Polarising effect.
I'm not using any form of filters for my still photographs but I'm noticing the effect of what looks like polarisation of the sky on many of my panoramas.


At 90 degrees to the sun the blue of the sky gets progressively darker and more saturated, just the sort of effect that a polarising filter will give. Is there some form of polarising effect from the standard filter on the front of the P4P lens?


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2017-2-15
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Alyn Walsh
lvl.2
Flight distance : 91407 ft
Ireland
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Nice Shot!
2017-2-15
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piowoc73
lvl.4
United States
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Which software did you use to stitch the panorama together? Any other post processing? Do you see the polarization effect in the single shots used for the panorama?
2017-2-15
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liningiv
Second Officer
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piowoc73 Posted at 2017-2-15 14:10
Which software did you use to stitch the panorama together? Any other post processing? Do you see the polarization effect in the single shots used for the panorama?

This is present in all the photos I used for this shot.
In a single image you see a very gradual change in saturation, but these panoramas cover more than 180 degrees, so the sky goes from virtually white near the sun, which is understandable to quite blue 90 degrees from the sun then very unsaturated at 180 degrees to the sun, exactly how a polarising lens would render the scene.
There is post processing in the sky, but that is graduated filter with exposure set to -1.5, but this still shows the unevenness in the sky.
2017-2-16
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piowoc73
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United States
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I assume you shot it in raw, with no effects applied in the app (saturation, hue, etc.).  For me it looks like the PL effect has been generated by the software you used for stitching the pano, but I may be wrong. Here is how you could check it: remove the front UV protection filter from the camera and shoot the same pano at the same spot and the same time of the day.
2017-2-16
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liningiv
Second Officer
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Fair idea, but 2 problems:
I won't be flying without that filter on to protect the lens.
And I was asked to stop flying in this place due to National Byelaws.
Still I got my images, and I can replace the sky with a far more interesting one from a different location.  thanks for the suggestions '73.
2017-2-16
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Cabansail
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Australia
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liningiv Posted at 2017-2-16 13:28
Fair idea, but 2 problems:
I won't be flying without that filter on to protect the lens.
And I was asked to stop flying in this place due to National Byelaws.

I am confused. In the OP you say that you are not using any filter at all. Then in this last post you say that you will not fly without a filter to protect the lens. So which is it?

I am assuming that the sky near the horizon is lighter due to some sort of mist which will give that graduated effect. Then when the saturation is pushed up it is emphasised.
2017-2-16
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liningiv
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Cabansail Posted at 2017-2-16 18:50
I am confused. In the OP you say that you are not using any filter at all. Then in this last post you say that you will not fly without a filter to protect the lens. So which is it?

I am assuming that the sky near the horizon is lighter due to some sort of mist which will give that graduated effect. Then when the saturation is pushed up it is emphasised.

There is a screw on filter on the front of all the Phantom 3 and 4 cameras.
"73 suggested that I remove the standard UV filter fitted to my P4P camera to find out if this is causing the effect.  I simply said that I would not fly without that filter fitted.
The polarising effect I am talking about is from right to left where the sky goes from almost white to blue 90 degrees away from the sun, then back to nearly white at 180 degrees from the sun, so it is not mist, but is typical of the effect of a polarising filter.
2017-2-17
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DJI-Jamie
DJI team
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United States
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Do you use manual or auto exposure?
2017-2-18
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piowoc73
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United States
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Hi,

I checked yesterday and it looks like the polarization effect of the stock UV filter is very weak, or almost non-existent for my P4P. I didn't do any panoramas yet, but for a single wide angle shot the sky looks natural, especially in DNG format. If you shoot JPG then the contrast and saturation are obviously pushed up, so it looks a bit different. The only remedy I could think about would be to try some other UV filters for P4P and see if they help. Obviously nobody would recommend flying without some protection on the lens
2017-2-20
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liningiv
Second Officer
Flight distance : 329409 ft
United Kingdom
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DJI-Jamie Posted at 2017-2-18 23:03
Do you use manual or auto exposure?

All taken in manual, 1/500 f5.6 ISO 100.
I am aware, after creating panoramas for more than 10 years, that the proximity to the sun will affect the brightness of the sky but the gradual saturation of the blue sky going from very light to dark then back to light over 180 degrees is normally a charachteristic of polarising the sky.

It is not a big problem but just wondered if anyone elese is noticing this.

The P4P is in my humble opinon the best camera in the sky, for the price, in the world right now, and by a looo-----ooong way.
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2017-2-20
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lienbacher
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Austria
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I am quite certain the issue you are having is of pure photographic non technical nature. The stock UV filter definitely does NOT polarize. It really is nothing but a piece of glass with bad coating. If you ever shoot against the sun remove it, the ghosting it causes is terrible. The DJI ND-Filters are much better coated! I decided for myself to not use it anymore. There is a second filter-glass right after the UV filter. I disassembled the lens and found that it does not have any optic characteristics at all, its really just a small thin also not brutally well coated piece of glass, so there is secondary protection for your lens.

But to your problem. You are shooting in high a huminity area. The closer your shot gets to the sun the brighter the water particles in the air become. It looks like polarizing, but it really is nothing but weather. If you check visibilty, you can hardly see further than 2-3km, everthing past that becomes fogged up. That's it.

Also making a living from photography for more than 10 years.
2017-2-23
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liningiv
Second Officer
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United Kingdom
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lienbacher Posted at 2017-2-23 12:42
I am quite certain the issue you are having is of pure photographic non technical nature. The stock UV filter definitely does NOT polarize. It really is nothing but a piece of glass with bad coating. If you ever shoot against the sun remove it, the ghosting it causes is terrible. The DJI ND-Filters are much better coated! I decided for myself to not use it anymore. There is a second filter-glass right after the UV filter. I disassembled the lens and found that it does not have any optic characteristics at all, its really just a small thin also not brutally well coated piece of glass, so there is secondary protection for your lens.

But to your problem. You are shooting in high a huminity area. The closer your shot gets to the sun the brighter the water particles in the air become. It looks like polarizing, but it really is nothing but weather. If you check visibilty, you can hardly see further than 2-3km, everthing past that becomes fogged up. That's it.

Thanks for your input lienbacker, and I can understand what you are saying, but if you look opposite the sun, the sky is getting less saturated again, and this is what led me to believe it is polarising.
2017-2-24
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