ND vs ND/PL

[russtanner6]

I'm new to both this website and the world of Mavic drones. I've had several Phantoms over the years.

I'm sure this topic has been discussed before, but maybe someone can give me a quick rundown.

I just bought these filters (based on a friend's recommendation): https://www.amazon.com/Polar-Filters-Filters-Cinema-Vivid-Collection (ND/PL). What is the main difference between these and straight ND filters? Do I need to buy ND filters also?

 

[jbishop129]

PL means polarized. The lens is 'circular polarized' or CPL as we refer to it in the photography world. You will want to thread on the filter, then rotate it to the desired angle of polarization. You often want to use a CPL when shooting near water, to cut out the harsh reflections. You often get more vivid colors as well.

 

[russtanner6]

PL means polarized. The lens is 'circular polarized' or CPL as we refer to it in the photography world. You will want to thread on the filter, then rotate it to the desired angle of polarization. You often want to use a CPL when shooting near water, to cut out the harsh reflections. You often get more vivid colors as well.

Thanks. Does having a CPL ever cause problems (something a straight ND filter would solve)?

 

[BaNZ]

I have the problem where I'm using the incorrect filter and destroying my good footage. So it really sucks if you don't pick the right ones.

 

[russtanner6]

I have the problem where I'm using the incorrect filter and destroying my good footage. So it really sucks if you don't pick the right ones.

What's an example of where you used the wrong filter?

 

[jbishop129]

Generally no, however there are some stylistic choices where it matters. For example, think of a scene where you see someone sitting on the train, and it is shot from outside the window. You see the reflection of what the train is passing by... Trees, buildings, etc...reflected in the window. With a CPL, you eliminate that, and would just see the person. Sometimes you want that reflection, and if you do its generally an aesthetic choice. Hope this helps!

 

[russtanner6]

Generally no, however there are some stylistic choices where it matters. For example, think of a scene where you see someone sitting on the train, and it is shot from outside the window. You see the reflection of what the train is passing by... Trees, buildings, etc...reflected in the window. With a CPL, you eliminate that, and would just see the person. Sometimes you want that reflection, and if you do its generally an aesthetic choice. Hope this helps!

That makes sense. Thanks. I probably need to play around with it. Putting the stylistic considerations aside, are the ND properties of a polarizing filter the same as a regular ND filter (in other words, are the reasons you would use an ND filter also accomplished with a polarizing ND filter)?

 

[jbishop129]

Yes thats correct. An ND/PL is literally the same as stacking a Polarizing filter on top of an ND filter. It just adds the polarization. Generally in the DSLR camera world, you would actually stack those filters, threading one on top of the other. With drones, especially a small one like the Mavic Air, you cant realistically stack the filters, so they make ones like this that are generally used together. I'd personally love to have a UV filter in there too, but that's a whole different discussion

 

[russtanner6]

Yes thats correct. An ND/PL is literally the same as stacking a Polarizing filter on top of an ND filter. It just adds the polarization. Generally in the DSLR camera world, you would actually stack those filters, threading one on top of the other. With drones, especially a small one like the Mavic Air, you cant realistically stack the filters, so they make ones like this that are generally used together. I'd personally love to have a UV filter in there too, but that's a whole different discussion

Awesome. Thanks. Do you know of any good YouTube tutorials on how to decide which type of filter to use?

 

[jbishop129]

I dont have a YouTube video, but here's an example of a shot I took recently, using an ND64 on my Mavic Air, so I could "Active Track" the car, and run a super low shutter speed (1/2 sec), giving that nice motion blur on the foreground:
Joe Bishop on Instagram: “Vetted #MotionBlur #Vette #Corvette #Arizona #Phoenix #PHX”

Dig around my Instagram, you'll find a few other examples, with our Range Rover and Tesla as well. It's something really fun to do with drone photography!

 

[gnirtS]

One thing nobody is mentioning here and one thing it seems on here a lot of people dont understand is how a CPL works and how to use it.
If you just stick it on the lens, unless you get very very lucky, the polarisation effect will be zero. For polarisation to work the filter has to be adjusted before fitting (best by looking at it and rotating) and fitted at that exact angle onto the lens.
Then it'll work provided the angle between light source and subject does not change - ie the drone points at the same angle the polariser was set at. If you rotate the drone, point it in a different direction, fly it to the other side, switch from landscape to portrait or anything else there'll be no polarisation effect. CPLs will not do anything if the light source is directly behind or in front either.

Most people dont adjust the things and go around thinking they're using polarising whilst actually not doing so.
The downside for video on this very specific method are typical drone shots such as an orbit or anything involving rotation will introduce different amounts of polarisation as it rotates so you get a strange, visible shift in color and reflections seen during the shoot.
For photos if you're doing panoramic shots you'll see clear light/dark areas in the sky as the field of view is wide enough to have no and full polarisation in the same shot.

For photos CPLs are great as you can set up the angle and shot prior to takeoff and get it. For video, as you typically move around more and alter those angles, they're not anywhere near as useful.

 

[jbishop129]

@gnirtS You're absolutely right, and thanks for taking the time to spell that out. As a photographer I often forget that not everyone knows how to properly use CPL's. Much like if you say "hey go to the store and get me some bananas", to someone who has no idea how to drive a car, there's some serious details missing in the request!

Back to your point, I had not thought about the impacts of CPL when you're changing directions as you mention, which is also completely correct. Orbiting around a POI with a CPL on is going to give some very weird footage, especially if what you're shooting has a lot of glass, surrounding water, etc. In those shots, you'd either just scrap the CPL and just use and appropriate ND, or, possibly, shoot the same shot several times with a repeatable waypoint flight pattern, adjusting the CPL angle, and deal with those clips in post. Though I think that'd probably result in a train-wreck, I've never tried that before. Hmmm... maybe I'll try that just to see what gives.