The Sigma 58mm WR (Water Repellent) 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.

A 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 multi-coated to eliminate internal ghosting and reflections. An anti-static coating serves to limit the accumulation of static electricity, making dust particles easier to remove or preventing them from adhering to the filter. Additionally, a water-repellent coating results in an improved beading effect when in contact with water, as well as oil, for greater cleaning efficiency while enhancing scratch resistance.
Sigma WR Circular Polarizer filters are constructed from optical glass with a black rim. Set within an aluminum-alloy filter ring that can be rotated in order to adjust the intensity of the polarization effect, the glass provides increased clarity as well as color fidelity while the black rim further ensures that reflections do not occur along the filter's edge.

1.25 to 1.4x Filter Factor    +0.3 to 0.5 Stops    Helps to Eliminate Reflections and Glare    Reduces Haze in Landscapes    Greater Color and Tonal Saturation    Black-Rimmed Optical Glass, Multi-Coated    Water, Oil, Static, Scratch Resistant    Slim Aluminum-Alloy Filter Ring    58mm Front Filter Threads    Knurled Front Edge, Plastic Case

Helps to reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface.

Polarizing filters arrange, and filter, directionally polarized light perpendicularly to the reflected light, allowing for the absorption of much of the light.

Clears up haze in distant landscapes and provides more saturated, vivid colors.

Strongest effect when used at a 90° angle from the sun.

Circular polarizers are ideal for use with digital cameras and autofocus lenses where a linear polarizer will often disrupt auto exposure and focus features.

Multi-coated to help eliminate internal ghosting and reflections.

Anti-static coating serves to limit the accumulation of static electricity, making dust particles easier to remove or preventing them from adhering to the filter.

Water repellent coating results in an improved beading effect when in contact with water, as well as oil, for greater cleaning efficiency while enhancing scratch resistance.

1.25 to 1.4x filter factor reduces exposure by 0.3 to 0.5 stops.

Constructed from clear, optical glass with a black rim which further ensures that reflections do not occur along the filter's edge.

Slim, aluminum-alloy filter ring helps to prevent vignetting and is durable while remaining lightweight.

Filter ring can be rotated to adjust the intensity of the polarization effect.

Knurled front edges provide a more textured grip when mounting or removing it from a lens.

58mm front filter threads allow for use with other filters.

Plastic filter case for storage and transport.

Related Questions and Answers

Q: 1. What is the light transmission of this?

A: Sigma does not have any published specifications for light transmission of this CPL (which I believe is typical because most CPLs have filter factors in a range) but does advertise a 30% increased transmission over their competitors' CPLs. This filter does have a 0.3-0.5 stop reduction of light, which equates to a theoretical numerical transmission of 81.2% (at 0.3 stops) to 70.7% (at 0.5 stops), the formula being 100% multiplied by half to the power of 0.3 and 0.5.

Q: 2. Will this work with a Lee Foundation Holder or a Cokin Z-Pro holder?

A: Unfortunately no, this filter will not work. Those filter systems require square or rectangular filters.

Q: 3. Different Hoya Circular Polarizer Filters (NXT, HD2, etc) have different filter factors. Is the polarizing effect independent of that factor? Or to state it a different way, does the filter have two effects - polarizing & neutral density? So would a CP filter with a lower (smaller) filter factor be just as effective at the polarizing effect as one with a larger (bigger) filter factor?

A: That is actually a great question. My main experience is with B&W HTC polarizers and the Hoya HD3's. The Hoya HD3 has become my favorite polarizer because it is so bright and easy to use. I'm not sure if the degree of polarization is the same because of the extra brightness, but it works SO well that it does not seem to matter if there is a small loss in any way. Also, the HD3 goes very nicely from warm to cool as you rotate it which is very useful. When I go back to my B&W polarizer it works well only on bright days when there is a lot of light - so to put it bluntly, the HD3 will spoil you in every way and is worth the money.

Q: 4. i have bought a sigma 77 mm polarized circular filter . I returned the first one after 3 days as I found small scratches on the glass and have now found considerable more scratches on the second after only three months prompting me to think that the quality of the glass or polarizing finish is not up to par . I am finicky about how and what I clean my filter with , and how I store my camera , so I know that what ever has caused the scratches can not be that significant , but maybe the glass is not as hard / strong as it should be. Can,t seem to find any specs on the grade or hardness of the glass used for these filters. Any body have any ideas ?

A: It is best if the filter comes with scratches to contact B&H customer service.Customer Service, can emailed at ord-status@a href= http://bhphotovideo.com, target= _blank bhphotovideo.com,/a or call them after 9am EST at: 800.221.5743 or 212.239.7765. Or you can talk to them in Chat.

Q: 5. Can the included 46mm filter (glass only) in this Sigma Circular Polarizer Holder BH #SIAP2900 - MFR #AP2900 be replaced with another 46mm curcular glass polarizer?

A: No, the Sigma filter is specific to the holder.

Q: 6. Does this filter work with the normal lens caps, or does it require a slip-on cap?

A: As the Hoya 77mm HD3 Circular Polarizer Filter has 77mm front filter threads, yes, you may use a standard snap-on 77mm lens cap on the front of the filter.

Q: 7. I've purchased this but when I rotate it I see no difference in the image. I bought this to remove reflections from windows but they remain just as strong as when I don't have the filter on. Am I doing something wrong?

A: The light needs to be at least partially polarized for a polarizer like this to work. If you are looking straight at the window and trying to remove reflections from behind you will see the least effect. You can experiment by putting yourself and the reflection you want to remove at an angle to the glass and you should start seeing more of an effect. You should find it is quite sensitive to the angle of reflection.

Q: 8. Will this work with the LEE Filters 105mm Accessory Front Thread Adapter Ring &H # LEFARPFK105?

A: yes, it will fit perfectly on the LEE Filters 105mm Accessory Front Thread Adapter Ring.

Q: 9. How thick is the frame?

A: The HD3 Cir/Pol filter is 5mm thick.

Q: 10. Is this a rotating filter for different darkness or is it just a straight one color?

A: A polarizing filter helps eliminate reflections, from shiny surfaces such as water, glass, etc. One can control unwanted reflections by rotating the filter to minimize or even eliminate reflections. This filter has no effect on colors.