Every photographer should have a circular polarizer. It removes glare from reflective surfaces such as water, glass and canvas. In the examples above and below I adjusted the polarizer to maximum effect, then turned it until there was little or no effect. The difference is substantial. The glare in the image below would be very difficult/impossible to address in post processing.
When buying filters you want to look for a well crafted product with a sturdy but minimal filter ring. It doesn’t take much for a filter to extend into the field of view and cause vignetting. The filters for Vu are constructed from German shott glass with beautifully machined threads in low-profile housings.
The effect is clearly visible through the camera, so you know when you have the filter properly oriented. Polarization works optimally at 90 degrees to the light source. So if you are shooting straight ahead and the sun is to your right at 90 degrees you should be able to get substantial polarizing effect. As you recompose moving more in line with the sun the effectiveness of polarizing will decrease. By the time you are aimed directly in-line with the sunbathe effectiveness is almost gone completely. If you have ever tried to polarize on overcast days, you probably noticed that no matter how you turned the adjusting ring, there was little or no change. cause polarization is so dependent upon the directionality of the light, overcast conditions result in the light being diffused or scattered to such an extent that there is no directional light to be polarized.
Some days it helps to be a MAC Group dealer. I needed to hold several different devices steady safely at one time. The laptop sits on a Kupo Laptop Table. The Nikon D4 is on a Induro BHL3s Ball Head mated to an Induro GLT304 Stealth Carbon Fiber Tripod equipped with a MCG23 geared center column. The iPhone 6+ is being supported by a Induro BHL2s paired with an Induro CT505 Carbon Fiber Trpod also with a geared center column. I thought it was an ingenious way to shoot video from the photographer’s point of view.