When it comes to enhancing images, a circular polarizer is probably the oldest trick in the book. It can change a pale sky to a deep blue one, turn foliage into a luminous super-green, light up autumn colours, saturate rainbows and even make water look crystal clear. The added contrast, saturation and clarity that a polarizer can give to images is nothing short of magic and every photographer should have one in their bag.
Contrary to its name, a polarising filter does not polarise light; it filters out polarised light. Light from the sun is polarised when it bounces off any non-metallic reflective surface like water, foliage or various air particulates. Polarised light robs images of colour, clarity and contrast and is in many situations undesirable. A polarizing filter removes this 'damaged' light and ensures that only unpolarised light reaches the camera sensor to produce a sharp, saturated and contrast-rich image.
For this reason, a polarizing filter is a very popular tool for any photographer, but especially for landscape photographers.
NiSi's PRO Nano HUC polarisers are made from top of the range optical pro glass, mounted in a brass ring and treated with a cutting edge water-repellant and scratch-resistant nano-coating. Brass threads don't jam nearly as easily aluminium.
What is the difference between a linear and circular polariser? Digital cameras' AF systems are not compatible with linear polarizers. When the world was transitioning from film to digital, linear vs. circular was a big debate, but it no longer is. For photographic purposes, you can assume that any polariser on the market nowadays is circular and not linear.