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martijn86's avatar

Filters: What does tiffens "SR" stand for?

Asked by martijn86 (393points) June 26th, 2009

Apart from tiffens liniear, circular, warm and low light polarizers, they offer “Polarizer SR”, which is only slightly more expensive then circular. But what is it? What does “SR” stand for?

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3 Answers

Harp's avatar

The “SR” stands for “Self-Rotating”. In other words, the mount allows you to turn the filter to adjust the polarization angle.

martijn86's avatar

Thanks, Self-Rotating makes sence, but isn’t that just what circular does?

Harp's avatar

Circular polarizers actually have two elements through which the light passes: first, a linear polarizer, then a quarter-wave plate. Most modern autofocus systems and internal light meters don’t function well with linear-polarized light; the quarter-wave plate takes that linear-polarized light from the first element and converts it to circularly polarized. The final result in the picture is very similar. Circular polarizers are just about making your camera’s electronics function properly.

“Self-rotating” is a designation that can apply to either linear or circular polarizing filters. It’s the style of mount. This distinguishes it from a drop-in mount, where you screw a separate filter holder onto the lens and drop in the filter disks.

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