The Hoya Alpha Circular Polarizer Filter helps to reduce reflections and glare by filtering out light that has
become polarized due to reflection from a non-metallic surface. The
light from the sun naturally becomes partially polarized due to
reflecting off electrons in air molecules, causing the light to scatter
into what appears as haze. A polarizing filter arranges, and filters,
this directionally polarized light perpendicularly to the reflected
light, allowing for the absorption of much of this light. This results
in a noticeable reduction of glare and reflections from non-metallic
surfaces and an increase in the saturation of skies and foliage.
circular polarizer only differs from a linear polarizer in that it
contains a quarter wave plane in addition to the linear polarizing
filter. The addition of this quarter wave plane is to circularly
polarize the linearly polarized light for the use of auto focus and
exposure functions. Due to how the light is broken down and filtered
with a linear polarizer, auto focus and exposure accuracy become skewed
during use. When the light becomes circularly polarized, it permits the
use of these functions.
This filter is non-coated and has
approximately 96% average light transmission. It is constructed from
optical glass and precision milled aluminum frames.