With my Spark I used a fixed (not circular) polarizing filter and the sky was uniform in color when taking spheres (tiny planets).  With my MA2 I got a circular polarizing filter(CPL) and have noticed lack of uniformity in the sky color...one area always being much darker.  I have seen they make ND/PL filters...do these rotate like the CPL or are they fixed liked my Spark was??? I primarily use the polarizing filter to reduce glare on water or foliage and have also found it makes colors more vivid/brilliant.  Am I using the CPL in the wrong situations???

Yep, polarises will make the blues and greens more vivid

Nice looking tiny planet.

Nice looking tiny planet.

Nice

That's a weird image, lol, school days diagrams of shooting a canon at the top of an EXTREMELY tall mountain come to mind

The polarizer is working as they do.  You will get the most polarizing effect about 90% from the sun (which is about right in your photo), and almost no effect pointing at the sun.  Polarizers shouldn't really be used in wide angle shots as you will get the effect as in your photo.  Just search for "using a polarizer" and you should be able to get some good tips on using one.

Ron

Am I using the CPL in the wrong situations???
A polariser is more trouble than it's worth on a drone and will give a horrible blotchy sky in a panorama.

Just to clarify something, you seem to be under the impression that "circular" in "circular polarizer" refers to either the shape of the filter or its ability to rotate. This is not the case.

The simplest type of polarizing filter to make is a "linear polarizer." When made for traditional cameras (not drones), a linear polarizing filter is still round, and still rotates to select the angle of polarization. The light coming through a linear polarizer is (wait for it) linearly polarized. This was fine for a long time, but once cameras got sensors for autoexposure and autofocus, polarized light started causing problems because those sensors could be more sensitive to some polarizations than others. Therefore, "circular polarizers" were developed, which put a quarter-wave plate behind the polarizing material, to convert the linearly polarized light to circularly polarized light, which does not affect the camera sensors.

You can't easily tell a circular polarizer from a linear polarizer just by looking at it (except by the markings printed on it). Circular polarizers used to be "premium" because of the extra layer, but I would guess almost all polarizing filters sold now are circular polarizers.

mph6563 Posted at 7-16 07:03
Just to clarify something, you seem to be under the impression that "circular" in "circular polarizer" refers to either the shape of the filter or its ability to rotate. This is not the case.

The simplest type of polarizing filter to make is a "linear polarizer." When made for traditional cameras (not drones), a linear polarizing filter is still round, and still rotates to select the angle of polarization. The light coming through a linear polarizer is (wait for it) linearly polarized. This was fine for a long time, but once cameras got sensors for autoexposure and autofocus, polarized light started causing problems because those sensors could be more sensitive to some polarizations than others. Therefore, "circular polarizers" were developed, which put a quarter-wave plate behind the polarizing material, to convert the linearly polarized light to circularly polarized light, which does not affect the camera sensors.

So when I see a PolarPro filter that says ND8/PL it's still a rotating type filter (CPL)???

Rustic17 Posted at 7-16 07:10
So when I see a PolarPro filter that says ND8/PL it's still a rotating type filter (CPL)???

ND8/PL is a rotating type filter, yes. And it will give weird results in most situations when shooting panoramas. Same goes for VNDs.

Rustic17 Posted at 7-16 07:10
So when I see a PolarPro filter that says ND8/PL it's still a rotating type filter (CPL)???

The whole point that I was trying to make was that  "rotating" and "circular polarizer (CPL)" are two unrelated things. A linear polarizer can rotate, and a circular polarizer can be fixed.

mph6563 Posted at 7-16 07:24
The whole point that I was trying to make was that  "rotating" and "circular polarizer (CPL)" are two unrelated things. A linear polarizer can rotate, and a circular polarizer can be fixed.

I'm no expect at this but I'd expect a circular polarizer to actually be fixed, and that the more traditional Linear polarizers would have a rotating mount.

mph6563 Posted at 7-16 07:24
The whole point that I was trying to make was that  "rotating" and "circular polarizer (CPL)" are two unrelated things. A linear polarizer can rotate, and a circular polarizer can be fixed.

Gotcha...thanks!!!

Smashey1 Posted at 7-16 08:31
I'm no expect at this but I'd expect a circular polarizer to actually be fixed, and that the more traditional Linear polarizers would have a rotating mount.

I have a Freewell CPL and it rotates.

Smashey1 Posted at 7-16 08:31
I'm no expect at this but I'd expect a circular polarizer to actually be fixed, and that the more traditional Linear polarizers would have a rotating mount.

No, that's not the case. A circular polarizing filter has a sheet of linear polarizer at the front of the filter, and a quarter-wave plate behind it to "undo" the polarization before it hits the camera's focal plane and sensors. The polarizing material still needs to be correctly aligned with the scene, just like it would for a linear polarizing filter, and therefore most polarizing filters (whether linear or circular) have a rotating mount.

mph6563 Posted at 7-16 09:03
No, that's not the case. A circular polarizing filter has a sheet of linear polarizer at the front of the filter, and a quarter-wave plate behind it to "undo" the polarization before it hits the camera's focal plane and sensors. The polarizing material still needs to be correctly aligned with the scene, just like it would for a linear polarizing filter, and therefore most polarizing filters (whether linear or circular) have a rotating mount.

Yeah...I'm most familiar with my Spark and it's PL filter just clipped over the lens with no rotation.

Rustic17 Posted at 7-16 08:44
I have a Freewell CPL and it rotates.

Got the same, does what it's supposed to.

Looks great.
And that is the exact thing PL filters do.
And also why you can't use them for pano's.
Or at least, you need to monitor the skies very closely.