How Filters Work
What It Does
When you here the word “Polarized” many negative things come to mind, well it’s the same in photography polarized light is something you don’t want and a Hoya Circular Polarizer filter can improve your photography.
Circular polarizing filters allow photographers to achieve creative, in-camera, effects not possible after the image is created. A polarizing filter simply filters out unwanted reflections from non-metallic surfaces such as water and glass in addition to light reflecting off moisture and pollution in the atmosphere. By rotating the filter you can select just the right amount of filtration needed to achieve the creative effect. This results in bluer skies, greener leaves, reduced or eliminated reflections, and greater clarity in your final image.
Darken Blue Sky – Sunlight becomes polarized by traveling through moisture and pollution in the atmosphere, a circular Polarizing filter blocks that light from entering your camera yielding clearer deeper blue skies with better contrast in the clouds.
Remove reflections – reflected light from not metallic surfaces is polarized and a circular polarizer can reduce or eliminate these reflection depending on the angle of your camera to the reflection.
Water – when photographing around water a circular polarizer and reduce the reflection to for deeper colors and to see more of what is beneath the surface.
Foliage – Leaves have a shiny side that is generally facing up or out, this shine can reflect a lot of light reducing the color saturation of the plant. A cicualr polarizer reduced the shine and allows the leaves natural colors to be seen and captured. This applies to days that are sunny or cloudy.
Glass – We’ve all seen lots of reflections off windows and other glass. A circular polarizer reduces or removes the reflections to see what is on the other side. Something that cannot be done later in any editing software.
Paint – Taking a photo of a house or car? Most paints are shinny and reflect more light then needed, which in turn lightens or washes out their color. A
How it works
Filters out Polarized Light
Polarized light is light who’s rays have been scattered due to pollution, moisture in the atmosphere and reflection. A circular polarizer filter only allows light rays that are traveling in one direction to enter the lens. This is how the Circular polarizer works it’s magic.
Here is a diagram of how a simple linear polarizer works.
The Hoya Circular Polarizers are actually made up of a piece of high quality optical glass followed by a linear polarizing film, this film, which is actually a micro screen, filters out the scatters light rays and only passes light moving in one linear direction. Modern camera meters and auto focus systems can have problems reading light moving linearly is a quarter wave plate is added behind the polarizing film to send the light into the lens in a circular pattern. This circularly polarized light will not interfere with any camera metering or auto focus systems.
Keep in mind that when any kind of light is filtered out, polarized or not, there is a reduction in exposure. That is how the circular polarizer darkens blue skies, it reduces the amount of light coming from the sky into the camera. That is why when a circular polarizer is rotated the shutter speed or aperture will change.
HRT vs. Standard
Standard high-quality circular polarizing film will reduce the amount of light entering the camera by 1.5-2.5 stops. HRT, or High Rate Transparency (High Transparency) polarizing film is both thinner and uses a slightly different material to filter out polarized light. The visual effect is the same and the benefit is that instead of the standard 1.5-25 stop light reduction, a High Transparency circular polarizer only reduced the light by 2/3-1 2/3 stops.