Nikon: bullet points after using circular polarizer and Cokin system

I have a Nikon D750 camera with a lens that has a focal length of 24-70 mm and a lens diameter of 72 mm. I bought a circular polarizer and filters from the Cokin P system with a wide angle filter holder. But there are some bullets at 24 mm. What system should I buy to remove bullets? Is the P system small and should I use XL? Cokin system with circular polarizer.

Cokin system without polarizer.

The first photo is with a Cokin filter and circular polarizer.
and the second photo is a Cokin filter without circular polarizer

Polarizer: Is the Cokin 173 filter just a back CPL?

Is the Cokin 173 filter just a back CPL?

No. The effect is similar to mounting your polarizer back, but much more pronounced in the Varicolor filter.

This is what my Hoya HD CPL looks like at polarization angles of 0 ° and 90 °, when it is oriented for proper mounting (male threads towards the camera):

  • Note that this is NOT a variable ND filter. In the image on the right, the filter darkens the light because the light source is polarized (it comes from an LCD screen, which uses polarization to control the light output).

Circular polarizer, 0 ° rotation, mounted correctlyCircular polarizer, 90 ° rotation, mounted correctly
Hoya circular polarizer, normal orientation, at 0 ° (left) and 90 ° polarization (right)

When you turn the polarizer backwards, this is how it looks, again at polarization angles of 0 ° and 90 °.

  • Note that the automatic white balance of my iPhone tried to adjust to the color change in both images. The left bluish mold of the polarizer is actually more pronounced than shown. You can see the yellow LCD monitor outside the CPL. The image on the left should have a cooler color temperature. Similarly, the yellow tone of the right image should be slightly heated (the monitor is a little more blue than normal outside of CPL view).

Circular polarizer, 0 ° rotation, reverse mountCircular polarizer, 90 ° rotation, reverse mount
Hoya circular polarizer, reverse mounting orientation, 0 ° (left) and 90 ° (right) polarization

I don't have the Cokin Varicolor, but I have the Singh-Ray Gold-N-Blue polarizer (same effect). Here is the Gold-N-Blue filter at 0 ° and 90 °, oriented for correct mounting:

Gold-N-Blue Singh-Ray polarizer, 0 ° rotation, mounted correctlyGold-N-Blue Singh-Ray polarizer, 90 ° rotation, mounted correctly
Singh-Ray Gold-N-Blue polarizer, normal orientation, at 0 ° (left) and 90 ° (right) polarization

Here is the Gold-N-Blue oriented for reverse mounting:

Gold-N-Blue Singh-Ray polarizer, 0 ° rotation, reverse mountGold-N-Blue Singh-Ray polarizer, 90 ° rotation, reverse mount
Singh-Ray Gold-N-Blue polarizer, reverse mounting orientation, at 0 ° (left) and 90 ° (right) polarization

I couldn't tell the difference between the Singh-Ray Gold-N-Blue filter mounted on front and back. But the degree of effect between Gold-N-Blue and a reverse mounted CPL is significant.

  • Also keep in mind that in real life, the effect of Gold-N-Blue (and Varicolor, I suppose) is not so pronounced to turn the world into Denver Broncos colors, or to make it look like a Michel Bay color film . Blue and gold / orange are extremely saturated here because the color-separated light of the LCD is already polarized (by definition being an LCD monitor).

Aerial photography: why does a polarizer lead to these strange images above the clouds?

A sheet of glass or plastic will typically have internal stresses. For glass and some transparent plastics, these lead to the birefringence patterns you see, when you make light (partially) polarized in them and then you see them through a polarizing filter. You can test this by using two polarizing filters, one in front and one behind, or holding the object in front of an LCD monitor and placing a filter in front. If your filter came in a clear case, it could be a good test object. You can find more information on the subject by looking for "polarizer" and "stress", "stress analysis" or "birefringence". In fact, the Wikipedia article on birefringence has a lot of information and some examples of images.

In its case, the sky provides a partially polarized light source, the airplane window produces the birefringence patterns and the polarizing filter makes them visible to the camera.