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Always Use PL Filters?

darioism

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Hey all,

I was shopping for ND and PL filters for my Mavic and came across the Polar Pro line. Looks like they have a few options for filters, with different stops and with or without polarization. However, I'm wondering why one wouldn't just get all polarized filters and use them any time you need an ND filter? If anything they can only make the image look better. And if you don't want polarization for some reason, just turn it 90 degrees to "disable" it and make it just an ND filter.

In other words, what's the downside to a polarizer filter which would result in a company selling polarized and non-polarized ND filters of the same value?

ND8/PL + 90 degrees = ND8 ?

Thanks in advance.
 
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From my understanding go PL's the effect changes on the angle tot he sun, so depending on the shot you are trying to take, you will have some polarisation creep into the footage if you are flying at different angles to the sun with multiple shots
 
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As above, polarisation angle is very specific, it needs an exact adjustment on the filter itself (to within a few degrees) and needs the light source to subject angle in flight to also be pretty much identical to get any real polarisation. Yaw the drone a few degrees can make the difference from polarising to none at all. We're not talking 90 degrees on the drone or filter here, we're talking 3-5 degrees.
Polarisation also only really works with the light source at 90 degrees to the camera (so sun left or sun right, not in front or behind).

As well as being impractical for video flying (installing, aligning and then keeping the drone at that exact angle) it can make panning shots look weird if you go into a zone of polarisation and back out etc.
For stills you still have the problem of having to exactly align it preflight and align the drone during flight but also if you're doing wide angle shots, particularly ones with a lot of sky in you end up with dark and light patches in the sky corresponding to areas of polarisation and areas without. Even a 3 shot vertical panorama is more than enough to demonstrate this.

Polarisers have their use for sure but its a very specific use and not really useful all the time (and can be detrimental). Most people don't seem to understand how they work or appreciate the pre-flight alignment needed and the fact that in flight they have to keep angles identical for it to do anything at all.
 
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Thank you for the responses. I am familiar with polarized filters and how to use them. But I'm not sure I stated the question properly.

Why is there an option to buy a non-polarized ND filter?

The way I see it, a polarized ND will either make the shot look better, or have zero effect on the shot, essentially making it just an ND filter. So why would anyone spend twice as much to get just an ND? Is there any benefit to using a non-polarized ND?
 
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You seem not to have read the post before yours.

The ND you can keep on anytime light calls for it. PL needs specific extra care and is not a good thing in all cases.
 
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The way I see it, a polarized ND will either make the shot look better, or have zero effect on the shot, essentially making it just an ND filter.

Lets try it again. You mean no bad effects OTHER than causing light/dark patches due to uneven polarisation on wide scenes or as the drone turns or large changes in exposure for the same reason (so flickering or just a nightmare to manage on manual exposure).
 
I am regularly using a PL filter for flying over water. I know its optical axis for reducing reflections on the water surface and know that I have to turn it for 90° for reducing reflections on windows. If I turn it to somewhat between it has almost no visible effect. So, if I would buy new ND filters I would always buy them combined with PL now and adjust them dependent on mission. I guess I will almost never run into a situation where the PL part would become to a disadvantage against a pure ND filter.
 
To give an example of uneven polarisation on the sky, there's one attached. Its a 3 shot vertical panorama stitched, manual exposure. Id forgotten to remove the CPL before the flight.
You can clearly see the dark patch of sky on the right hand side that then lightens again as you get away from it. A photo ruined as you can't see the patches on a screen down below. It also shows how narrow the band of effective polarisation is as a side effect.
You'll get similar sky colour changes on panning videos and so on as well.
 

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    DJI_0652-Pano.jpg
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Ah, I understand now. I'm used to shooting stills but I see what you mean about panning shots. Thanks everyone!
 
As above, polarisation angle is very specific, it needs an exact adjustment on the filter itself (to within a few degrees) and needs the light source to subject angle in flight to also be pretty much identical to get any real polarisation. Yaw the drone a few degrees can make the difference from polarising to none at all. We're not talking 90 degrees on the drone or filter here, we're talking 3-5 degrees.
Polarisation also only really works with the light source at 90 degrees to the camera (so sun left or sun right, not in front or behind).

As well as being impractical for video flying (installing, aligning and then keeping the drone at that exact angle) it can make panning shots look weird if you go into a zone of polarisation and back out etc.
For stills you still have the problem of having to exactly align it preflight and align the drone during flight but also if you're doing wide angle shots, particularly ones with a lot of sky in you end up with dark and light patches in the sky corresponding to areas of polarisation and areas without. Even a 3 shot vertical panorama is more than enough to demonstrate this.

Polarisers have their use for sure but its a very specific use and not really useful all the time (and can be detrimental). Most people don't seem to understand how they work or appreciate the pre-flight alignment needed and the fact that in flight they have to keep angles identical for it to do anything at all.

Kudos, to this beautiful explaination. Makes it very clear why to use PL and ND as seperate filters. Thanks for sharing.
 
@darioism This is a massive oversimplification, but the main use of polarized filters on the drone is to reduce/eliminate surface reflection on water. The polarization can be used to enhance video in general, but the problems are well discussed above.
 
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