The 138mm Schneider Unmounted ND Circular Polarizer Filter is a filter that combines a solid neutral density effect and a circular polarizer effect within a single glass surface. The solid neutral density effect provides an exposure reduction of 3 stops. Its 0.9 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than would normally be required. By slowing your exposure time or increasing your aperture, you are able to control depth of field and convey movement more easily.

Along with this filter's solid neutral density effect is a circular polarizer effect that is simultaneously applied to help 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 138mm Unmounted Neutral Density 0.9 Circular Polarizer Filter is constructed from water white glass for increased optical clarity as well as color fidelity. It is 138mm in diameter and unmounted for use in third-party or custom filter holders.

0.9 Optical Density    Non-Coated, Water White Glass    Unmounted Solid Neutral Density Filter    For Third-Party or Custom Holders    Darkens Entire Image    Allows Reduced Shutter Speed    Allows Wider Aperture    Integrated Circular Polarizer Effect    Helps to Eliminate Reflections and Glare    138mm Diameter, Filter Pouch

0.9 neutral density filter effect darkens the image, allowing you to photograph with a longer shutter speed or wider aperture than normally required and is combined with a circular polarizing effect to help reduce reflections and glare by filtering out light that has become polarized due to reflection from a non-metallic surface

8x filter factor provides a reduction of 3 stops; neutral density filter effect allows you to control depth of field and convey movement more easily

Polarizing filter effect arranges, and filters, 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 polarizing 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

Constructed from water white glass for increased optical clarity

Non-coated

Unmounted for use in third-party or custom filter holders for film and television cameras

Padded pouch included for storage and transport

Related Questions and Answers

Q: 1. Does this produce an X-Pattern at max ND?

A: It does at just beyond max, I just back it off a tiny bit and it's fine. The ND range is large enough that if you need to go beyond max, it's a sign that adjusting the ISO a touch might be a good idea.

Q: 2. Why does it say 86mm and 82mm?

A: The rear filter thread is 82mm and the front thread is 86mm.

Q: 3. Can you stack PolarPro ND filters?

A: The PolarPro 82mm ND1000 QuartzLine Solid Neutral Density 3.0 and Circular Polarizer Filter (10-Stop) have front filter threads, so you could stack them with other filters.

Q: 4. Can I put it on a sigma 30 mm lens?

A: In theory you could with a step down ring, but you'll get vignetting on the edges. I'd recommend getting the correct 52mm filter.

Q: 5. Can you turn the polorizer the entire way off on this filter?

A: The polarizing effect on the K&F Concept Nano-X ND2-32 Variable Fader & Circular Polarizer HD Green Coated Waterproof Anti-Scratch Japan Optics Filter (77mm) can be reduced, but not turned off.

Q: 6. What lens cap will fit this 77mm filter?

A: You may use any 77mm lens cap. Here are some examples https://www.bhphotovideo.com/c/product/806450-REG/Sensei_lc77_77mm_Center_Pinch_Snap_On.html or https://www.bhphotovideo.com/c/product/850508-REG/Sony_ALC_F77S_ALC_F77S_77mm_Front_Lens.html

Q: 7. I have a Canon 24-105mm f4L(77mm). I already have a 77mm protective filter on it; with threads, so I can stack another filter. What size ND filter should I order?

A: Protective filters have the same size front and rear threads so a 77mm variable ND would be recommended.

Q: 8. Does it have hard stops?

A: It is smooth. Most variable ND filters are smooth so make the transition smoother in video.

Q: 9. What can I use as a front cap for this item (dont tell me Schneider 86mm Push-On Cap because it does NOT fit)?

A: This Sigma LCF-86 III 86mm Lens Cap is compatible with the Genustech 82mm Variable Neutral Density and Circular Polarizer Filter. https://www.bhphotovideo.com/c/product/1168370-REG

Q: 10. Do these filters have cross polarization X?

A: No, they don't.