A polarization filter or polarizing filter for short, only lets light through from one vibration level. Normal daylight and artificial light consists of rays of light that oscillate on all levels. On non-metallic surfaces, however, the light that oscillates perpendicular to it is reflected more strongly. If the polarizing filter is then set at a 90° angle, these light components are darkened. This effect can reduce reflections on glass, water surfaces and other smooth surfaces.
This also makes leaf green appear more intense and the sky takes on a darker blue color. This effect is most intense when the sun is at an angle of 90° to the picture section, aligned directly against or with the sun; the polarizing filter has little effect. With strong wide-angle lenses that depict a large angular range, the effect can therefore vary in intensity in the depicted part of the sky, which is occasionally annoying.
A distinction must still be made between linear and circular polarizing filters Canon Control Ring Mount Adapter EF-EOS R, but it would lead too far here to explain this difference further. Ultimately, however, circular polarizing filters are used almost exclusively in photography at the moment. If you are interested, there are further details, for example, on Wikipedia.
The image above is taken from the same position as the one shown above with the ND-3 filter. Incidentally, post-processing in Light room was the same for both images. But this time I used a polarizing filter (B&W Käsemann). The exposure time was now only 1/80 second. In comparison, you can clearly see that the green of the leaves appears much more intense, the sky shows a somewhat more intense blue, the clouds are structured more clearly and the waves on the water are now clearly visible.
I use the polarizing filter very often for landscape and city shots with a clear sky.
Back to Mount Adapter Drop-In
Why did I buy this adapter now? As a long-time Canon photographer, I now have a very large inventory of Canon EF lenses, which I would like to use on my new mirrorless Canon EOS R5 for the time being. I also want to keep using my trusty Canon Control Ring Mount Adapter For R3 and it can only be used with EF lenses. Some of these EF lenses are also not yet available for the new RF mount. Canon was aware of this fact when presenting the EOS-R system and has therefore opened up the possibility of continuing to use the existing EF lenses via EF-RF adapters.
In contrast to third-party solutions such as Sigma (MC-11) for Sony alpha cameras, Canon R cameras even support EF lenses natively. Therefore, the performance remains at least on the same level as the Canon DSLR housings. Some lenses, like my TS-E 17mm or the 85mm f/1.2L II, work even better on the EOS R5 than before. You can find more information about this in my review of the Canon EOS R5 .
Comparison of filter types
In the picture above I have placed the two filter types next to each other. The screw filter on the right is a high-quality, multi-coated model from B&W Käsemann * with a 77mm thread. If you compare the gray values in the picture above, you can already see that the screw filter absorbs a little more light than the drop-in filter. Since both filters are on a white background and the incident light therefore passes through the filters twice, they appear darker here than in transmitted light.
Since many lenses have different filter diameters, you need several filter sizes or you have to adapt larger filters with adapter rings, which mean a lot of fiddling. The lens hoods often no longer fit either.
I have used a very high quality 77mm filter (B&W Käsemann) that fits my Canon Control Ring Mount Adapter For R5 from 16-200mm.
Even with the same filter diameters, the filters also have to be changed when changing the lens or you need several of them, which costs a lot of money. There are also some lenses that do not offer the option of using screw filters due to protruding front lenses, or that have such a large filter diameter that the filters are disproportionately large and expensive.
This currently applies to 3 lenses for me: the TS-E 17mm, my Sam yang 14mm and my Sigma DG OS HSM 60-600mm (with 105mm filter diameter!). With wide-angle lenses, you could use filter holders that are attached in front of the lens, but these are also very bulky, expensive and difficult to assemble.