How do people mount their polarising filters ?

[Storyline]

I have got a set of ND filters and read some advice to get some that were polarised which sounded sensible especially as most of my video will be taken around water.
Before mounting one I tried to find the 'active' part of the filter when at 90 degrees to the sun but it is so small I found it near impossible. This coupled with the fact that our aircraft are flying at various incidences to the sun leave my experience of PL on dSLR cameras irrelevant

So how do most people use them - surely it isn't just trusting to luck that you have it right ....

 

[gnirtS]

I have got a set of ND filters and read some advice to get some that were polarised which sounded sensible especially as most of my video will be taken around water.
Before mounting one I tried to find the 'active' part of the filter when at 90 degrees to the sun but it is so small I found it near impossible. This coupled with the fact that our aircraft are flying at various incidences to the sun leave my experience of PL on dSLR cameras irrelevant

So how do most people use them - surely it isn't just trusting to luck that you have it right ....

You're right - polarisers only work for very specific angles of light to subject and need to be set up exactly right for that prior to the flight so for MOST peoples method of flying and recording they're fairly useless.

Before a flight i take my sunglasses off (they're polarised....) face the direction i know i want to take the shot from, gradually rotate the filter until the sky darkens or reflections disappear. Then look at the writing on the side of the filter to see its orientation.
I then fit it on the drone at that exact orientation. Then take off, fly, take the photos i want.
Turn the drone, no effect any more, different subject angle, no more effect etc.

For video you need to know exactly what shot you want. Worst case, if you rotate the drone with a PL on you're going to get a drastically different exposure for bits of the sky depending on which area is being polarised at the time. If you use manual exposure this is really obvious.
Also with stills, wide panoramas and 360s will have light/dark areas of sky due to them so dont use it for that.

Polarisers and ND filters seem to be misunderstood a lot amongst drone users. Most done even realise they need to setup prior to the flight and keep the exact angles in the air.
Also remember polarisers have no effect directly into or away from a light source so people using them to take photos of sunsets and so on aren't actually using them for anything.

They're REALLY handy tools but need specific planning of the shot before flight, careful pre-flight adjustment and fitting then the knowledge if you deviate from those angles its not going to do anything. So its all about knowing what you want before flying.

 

[Mossiback]

On a SLR camera the polarizing filter has a mark on it that you basically just rotate until it is pointed toward the sun. When the mark is on the top of the filter the polarizing filter is set horizontally. My MP PolarPro filters had no mark so I had to make my own. While wearing polarized sunglasses, look through your filter and rotate until the most light is blocked out, then mark the filter rim at the 3 or 9 o'clock position. When you mount the filter with the mark on the top or bottom of the camera lens it is mounted with the polarizing effect set horizontal. This is where I set mine if I do not have a particular shot angle worked out ahead of time.

 

[gnirtS]

All the CPLs i have have writing on the side bezel (polar pro, NDxx-PL) or whatever. This typically covers most of the outside of the filter. So after setting it visually i just look at it and go "The P of Pro is at 12 o'clock" or whatever then fit it on the drone that way.

 

[Storyline]

Thanks for all the really useful info. This is all so new to me but I have realised one thing that gnirtS mentioned and that is I need to plan my shots. I have never taken video so at the moment I am just going up and filming and then I imagined I would just edit the footage into something. I need to decide what I am planning to achieve, then I can plan the shots I need and set the camera up accordingly which should make things easier.

 

[Storyline]

All the CPLs i have have writing on the side bezel (polar pro, NDxx-PL) or whatever. This typically covers most of the outside of the filter. So after setting it visually i just look at it and go "The P of Pro is at 12 o'clock" or whatever then fit it on the drone that way.

I have the Polar pro filters and as you say they have writing top and bottom so it should be easy to mount them when I have used the sunglasses technique.

 

[Mossiback]

I have the Polar pro filters and as you say they have writing top and bottom so it should be easy to mount them when I have used the sunglasses technique.

It will be easier to mark them. My set of three PolarPro filters all have the orientation to the printing at different angles. Given the importance of correct orientation it astounds me that they do not come with the orientation marked.

 

[gnirtS]

It will be easier to mark them. My set of three PolarPro filters all have the orientation to the printing at different angles. Given the importance of correct orientation it astounds me that they do not come with the orientation marked.

Because orientation changes and thats the problem. Reflection vs direct light and so on.
The "correct" orientation is going to depend on angle between light source and subject and will change depending on if youre dealing with reflected or direct light etc so there is no one size fits all set "markings". As with a proper CPL on a camera, it needs constant adjusting as you move.

 

[Mossiback]

Because orientation changes and thats the problem. Reflection vs direct light and so on.
The "correct" orientation is going to depend on angle between light source and subject and will change depending on if youre dealing with reflected or direct light etc so there is no one size fits all set "markings". As with a proper CPL on a camera, it needs constant adjusting as you move.

You are right, you need to set the filter for the proper angle. You cannot do that unless you know where "horizontal" is on the filter. Marking it at horizontal makes it easier to set the angle for the shot. SLR polarizing filters have this mark on them so you can rotate it while on the camera, pointing the mark toward the sun.

 

[gnirtS]

Not a single one of my DSLR filters have such a mark because it doesn't actually work. You need to do it visually, by looking through the filter and rotating until you see the effect kick in. And THATS you angle. And it can vary by any number of degrees when dealing with reflections.

Quite simply, knowing where horizontal and vertical is doesn't help when you're dealing with changing light angles and reflection angles.

This is worded by someone else far better than i could:

The effect of a polarizing filter is determined not only by the position of the filter in relation to the horizon or ground, but is also dependent upon the angle(s) of the light illuminating the scene. Imagine you are shooting outdoors in bright sunlight. To get a similar effect when the sun is low on the horizon to your left as when the sun is low on the horizon to your right requires a different position of the filter. When the sun is higher overhead would require yet another position. When the sun is behind you and above requires a different position than when the sun is above and in front.

Thats also why polarised sun glasses dont always have optimum polarisation (especially again around reflected light) and you tilt your head to get the effect stronger and so on.
The only way to set up a CPL is to get at the correct angle, look through it and rotate. Markings dont do anything.

Direct light its not too inaccurate (but far from perfect). But a lot of the use of a polariser is to eliminate reflections. This completely changes the angle of light hitting the filter meaning that mark which you've previously used to align for direct sunlight no longer has any use.

 

[Mossiback]

Not a single one of my DSLR filters have such a mark because it doesn't actually work...The only way to set up a CPL is to get at the correct angle, look through it and rotate. Markings dont do anything...

I don't want to keep debating this, but all of my DSLR polarizers are marked with a small dot. Of course it really is not needed for a hand-held camera because you can easily rotate while looking through the lens to get the desired effect. This is not possible to do when the camera is flying. If your filter is marked to show horizontal orientation you can mount it with the mark set to the best guess for the shot. The mark at least gives you a starting point.

 

[gnirtS]

If your filter is marked to show horizontal orientation you can mount it with the mark set to the best guess for the shot. The mark at least gives you a starting point.

You can, or you can toss a coin. Just as much chance as being correct. The only way to actually do it is by doing it by eye with the lighting conditions replicated, ideally looking at the same target.
The horizontal markers do nothing, thats why most manufacturers dont put them on and absolutely nobody says to use them.

 

[Storyline]

This is what mystified me as my only experience is on a stills camera where the filter has its sweet spot relative to the angle of the sun at that moment in time vs your position to the sun. If you want maximum polarising effect you have to shoot in the direction where it is most effective (does that make sense . As you zoom around the sky this must be constantly changing. On the other hand the effect of eliminating reflection from water when wearing polarising sunglasses seems to be at all times - have to find out more !

 

[Storyline]

It would be useful if Polar pro (who seem to be the market leaders) would at least put a simple scale ring round the filter so when you have found the sweet spot for the shot you want you could mount it on the gimble more easily. The thing is so tiny that any variance must make a difference.
A bit off topic but another thing they could do is improve the case which comes with some of their filters. When I got my set of three they came with a nice little box but when I got my single 32 it came with a near useless pouch which even when closed with its drawstring allowed the filter to drop out. That actually cost on a per filter basis considerably more than the set of three so a little plastic box is not too much to ask for imo

 

[Thwyllo]

I have five DSLR CPLs and only one has a white dot - which if you used it, is meant to point at the source of the light you want to polarize.

As @gnirtS says, the whole point of a DSLR (and SLRs for that matter) is that you don't **** about adjusting filters separately, you just tweak them while you're looking through the viewfinder - that way you see exactly what you're getting.

So my question is (and I don't use them so I don't know how they're mounted) why not adjust them while pointing the drone in the general direction you want to take your shot and turn the filter while looking at the camera feed on your phone/tablet? Takes away the guesswork, although it will still only be any good in one fairly narrow and static field of view.

 

[Storyline]

.....
So my question is (and I don't use them so I don't know how they're mounted) why not adjust them while pointing the drone in the general direction you want to take your shot and turn the filter while looking at the camera feed on your phone/tablet? Takes away the guesswork, although it will still only be any good in one fairly narrow and static field of view.

The problem with this is that it is impossible to rotate them once mounted on the camera as they go on with a very snug fit. It may be possible to offer them up to the lens the wrong way round and rotate them that way but it would be difficult and also I am not sure if they are circular or not. If not they would not work the wrong way round. Anyway, best not just type about it I should really get the Mavic out and have a go ! (only problem is that we have thick cloud here)
Think I will send an email to Polar pro and ask them. I will put their reply on this thread .....

 

[Thwyllo]

So hang on, a DSLR polarising filter sits and rotates in its own mount - is it not the same for these drone-specific versions?

I'm assuming it doesn't really matter if they are linear or circular - circular are more relevant to DSLR technology because they obviate metering errors that can arise because of the prism mirror. Linear are actually better and cheaper, and your comments about mounting them implies that's what these are, which makes the prices being charged for them by some suppliers pretty crappy frankly.

EDIT: I was wrong; their writeups say they're CPLs not linear. So I revert to my earlier suggestion... It's messy but literally hold them in front of the camera, pointing at the direction you want to film or photograph, while viewing the camera feed and their effect ought to be visible.

If you can pat your head at the same time you win extra points....

 

[Storyline]

Thwyllo, in theory it should be possible but I know from experience with my dSLR that in sub-optimum conditions it can be difficult to see the sweet spot so on the Mavic it would be near impossible but I will try !

 

[JoBri]

just rotate until it is pointed toward the sun.

 

[gnirtS]

So my question is (and I don't use them so I don't know how they're mounted) why not adjust them while pointing the drone in the general direction you want to take your shot and turn the filter while looking at the camera feed on your phone/tablet? Takes away the guesswork, although it will still only be any good in one fairly narrow and static field of view.

My only fear doing that is just how weak, fragile and floppy the MP gimbal is.
I did attempt it and found it difficult to adjust - if its own tight enough to not fall off trying to rotate it was twisting or moving the gimbal. I only ever fit and remove filters with the gimbal clamp on and drone powered off as its so delicate.
Yes it'd be the best method in theory for doing it but in practice its surprisingly fiddly and ive got doubt it wont break something.

On my CPL there is enough writing on the edges to get the alignment good enough when fitting with a bit of practice.

Edit:- and no they dont have a separate rotation part. Im guessing due again to the weak gimbal they're VERY sensitive to extra weight and a COG shift and would likely throw up a gimbal error.
Even not-so-good NDs that are a tiny bit heavier than others cause a gimbal error on startup.