The FotodioX WonderPana FreeArc Core Unit for Sigma 20mm Art Lensis compatible with the FotodioX WonderPana 145, FreeArc, and Absolute filter holder systems. It helps to reduce reflections as well as 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.

The FotodioX 145mm Circular Polarizer Filter is constructed from optical glass for clarity as well as color fidelity and features lightweight, aluminum-alloy filter rings. A rear filter ring connects to a compatible filter holder while four brass knobs along the side of the front filter ring allow the filter glass to be easily rotated. This provides the ability to achieve the desired degree of polarization even if another filter is placed in front of the FotodioX 145mm Circular Polarizer Filter.

For Sigma 20mm f/1.4 DG HSM Art    WonderPana FreeArc Core Unit    Use with WonderPana 6.6" Holder Bracket    With Bracket, Holds 6.6" Wide Filters    Holds up to Two 6.6" Wide Filters    Combine a 6.6" Wide and a 145mm Filter    145mm Solid Neutral Density 3.0 Filter    1000x Filter Factor, 10-Stop    145mm Circular Polarizer Filter    Helps to Eliminate Reflections and Glare

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.

1.25 to 8x filter factor reduces exposure by 0.3 to 3 stops.

Constructed from optical glass for clarity.

Lightweight, aluminum-alloy filter rings along with four brass side knobs allow the filter glass to be easily rotated. The desired effect can be easily achieved even if another filter is placed directly in front.

Filter pouch included for storage and transport.

Related Questions and Answers

Q: 1. I have the Nikon D750 and want to see if anyone has used this Sigma lens with that camera and if they are fully compatible?

A: Thank you for your interest in Sigma products. The 20mm f/1.4 DG HSM Art Lens for Nikon F is compatible with the Nikon D750.

Q: 2. Can this filter holder work with the Rokinon DSX 14mm cinema lens ?

A: No, the FotodioX WonderPana 145 Core Unit Kit for Rokinon/Samyang AF 14mm f/2.8 RF/FE does not fit the Rokinon DSX 14mm cinema lens.

Q: 3. is this a weather sealed lens?

A: The 20mm f/1.4 is not weather sealed, no.

Q: 4. Is the 20mm 1.4 manual focus powered by wire? or is it real manual focus?

A: The focus adjustment ring is fully mechanical, not electromechanical/by-wire. Note that the lens provides auto-focus as well.

Q: 5. Can I stack both filters and will it cause vignetting?

A: Yes, it will but only at very wide apertures

Q: 6. what is the focal length on the GH4 paired with the Metabones 0.64X?

A: I am using it on a Nikon 750 so I don't have a clue. I do know this is no small lens and I always wonder about pairing lenses like these with smaller cameras. Nice piece of glass anyway. Have fun !! Gregg

Q: 7. What pouch fits this lens?

A: Sigma 20mm f/1.4 DG HSM Art Lens for Canon EF dimensions are 3.57 x 5.11" / 90.7 x 129.8 mm. This lens comes with it's own padded case in the box. If you prefer a neoprene lens pouch the following option will fit the lens with the lenshood on reverse. LensCoat LensPouch (Medium Wide, Black) BH #LELCLPMWBK • MFR #LCLPMWBK https://bhpho.to/3Vhexeb

Q: 8. How does the image quality of this lens compare to that of Nikon 20mm 1.8?

A: This lens has a much better image quality overall then the 1.8 version from Nikon. It really does produce a spectacular image that will wow you. Sigma really nailed the Art series. I am a loyal Nikon shooter and this is the only non Nikon lens in my bag, but very glad I bought it.

Q: 9. Does this lens have image stabilization?

A: Yes... I use a Sony A7ii with this lens and it is compatible with Sonys image Stabilization.

Q: 10. Does it have image stabilization

A: No image stabilization.