In transparent tape, long polymer molecules are stretched parallel to the length of the tape. Light polarized parallel to the stretch of the molecules travels through the tape more slowly than light polarized perpendicular to the stretch.

When a second piece of polarizer is placed over the tape and rotated, it transmits different colors at different angles. This accounts for the color combinations you see at a given angle, and for the changes in color as the polarizer is rotated (click to enlarge diagram below).

A denser filter, like a 6-stop or 10-stop will allow the photographer to select even slower shutter speeds for increased motion blur:

What is planepolarized lightin Chemistry

The thicker the tape is, the more out of step the components will become, and the greater the change in the polarization will be. If, for example, the two waves recombine after one has been delayed by one-half a wavelength, the direction of polarization of the light will be rotated by 90 degrees.

Vignetting is determined by the amount of light fall off toward the outer edges of your lens. The wider the lens you choose and the longer the exposure time you have, the more vignetting can occur. Poorly designed and manufactured filters will increase the amount of unwanted vignetting. A quality filter will either have no color shift at all, or, at the very least, have predictable results.

Circularlypolarized light

The colors you see here result from differences in the speed of polarized light as it travels through the transparent tape.

When polarized light enters the tape, its direction of polarization will probably not line up with the length of tape. If the light is polarized in a direction that does not line up, its direction of polarization will be resolved into two perpendicular components. One of these components will be parallel to the length of the tape, and one will be perpendicular.

Linearlypolarized light

Using transparent tape and polarizing material, you can make and project beautifully colored patterns reminiscent of abstract or geometric stained-glass windows. Rotating the polarizer as you view the patterns makes the colors change. With a little creativity, you can also create colorful renditions of objects or scenes.

Almost all ND filters have some sort of color shift. When an image is produced that has a green color cast, it is often the result of a poorly designed filter. On the other hand, when infrared (IR) light penetrates the camera sensor, the resulting image can have a magenta cast.

Plane-polarizedlightexamples

Neutral Density (ND) filters reduce the intensity of all wavelengths, or colors, of light equally from entering the camera, in measured amounts. This allows the photographer more control in selecting shutter speed and aperture combinations in a variety of conditions.

Polarization oflightnotes PDF

There are several variables including weather, time of day, ambient light, etc... that will determine which neutral density filter is appropriate for the occasion. It is up to the photographer to select the right shutter speed and corresponding filter to make an otherwise ordinary shot something more powerful.

Variable ND filters are essentially two polarizers placed together with one plane preventing a fixed amount of light and the other rotating to prevent incremental amounts of light from entering the camera.

Color shift is amplified by low-quality materials, poor manufacturing, and ignoring the infrared band of the light spectrum.

A note about the tape used in this Snack: Before you buy large quantities of transparent tape, test the brand you're buying by placing a strip of the tape between two pieces of polarizing material. For convenience, you can actually stick the tape to one of the polarizers, and then rotate the other polarizer against it. If the tape changes from dark to light, or vice versa, you can use it in this Snack. If the tape remains the same shade of darkness when you rotate the polarizer, it won't work here.

Polarizedand unpolarizedlight

The liquid crystal displays (LCDs) on most computer monitors and laptop screens polarize the light that comes from them. You can verify this by looking at a LCD screen through one of your polarizers. You can try this Snack by putting tape directly on a LCD screen. The tape will look clear, but you can reveal the mosaic any time by looking at the screen through a polarizer.

Planepolarized lightenantiomers

Variable ND filters can be advantageous to the photographer on the go. Carrying a set of fixed ND filters and constantly changing fixed filters can be cumbersome and time-consuming. With a variable ND, the photographer can just rotate the filter like a polarizer to get the desired effect.

White light is made up of light of all different colors, or wavelengths. Since the index of refraction of the tape is different for each color of light, each color has its own unique pair of speeds as it passes through the tape. The result is that the polarization of each color is changed by a different amount for a given thickness of tape.

Polarized lightmeaning

Fixed ND filters come in a range of densities to meet the needs of the photographer and the conditions they might be shooting in. A lighter density filter, like a 3-stop, will allow the photographer to select a shutter speed 3 stops slower:

Every material has an index of refraction, which is the ratio of the speed of light in a vacuum to the speed of light in the material. Light travels through the tape you used in this demonstration at two different speeds. (Materials with this property are called birefringent, which is derived from the Greek words for “doubly refracting.”)

The waves that compose these two components are initially in step with each other. But as they travel at different speeds through the tape, they go out of step—that is, the crest of one wave no longer lines up with the crest of the other. When these out-of-step light waves emerge from the tape on the other side, they recombine, making light with a polarization different from that of the original light.

Fixed ND filters, also referred to as solid ND filters, have coating(s) evenly distributed across the frame of the filter. The density of the filter is predetermined.