Tiffen filters are manufactured using ColorCore technology, a closely guarded proprietary process that entails permanently laminating the filter material in between two pieces of optical glass that are ground flat to tolerances of a ten-thousandth of an inch, then mounting them in precision metal rings.
The ColorCore process allows Tiffen to control the color and density of Tiffen filters, and the characteristics of special effects filters with much greater accuracy than typical dyed-in-the-mass filters, which usually exhibit color and density variations. When Tiffen filters are ground and polished, the Colorcore is unaffected, so color and density remain uniform. Indeed, when you hold a group of Tiffen filters of the same type against a white sheet of paper, they all look identical -- because they are! Try this with or competitor's filters and you're likely to see slight variations. Maybe that's why most top Hollywood motion picture studios rely on Tiffen filters for their multimillion-dollar productions, or why Tiffen can custom-make an exact replacement for them if one breaks on the job. That's consistency and excellence - two pretty good reasons why, when it comes to filters, you should rely on Tiffen too.
Polarizing Filters provide color and contrast enhancement. Reflected light often shows up as whitish glare that washes out color in an image. A Polarizer corrects this problem producing deep, dramatically blue skies. It also removes glare from non-metallic surfaces, such as windows and water. Color saturation in general, especially outdoors, can be improved significantly.
Note: A Circular Polarizer has the same effect as a standard Rotating Linear Polarizer and is used on cameras with beam splitting metering systems commonly found on auto-focus SLR's (for most 35mm auto-focus cameras see your camera manual).