To avoid dark corners, K&F Concept ND2-ND400 filters are designed in ultra-wide construction so the front side of the ND filter is one size larger than the camera lens. It is recommended to use a lens hood of a larger size. 

First, K&F Concept ND2-ND400 lens filter allows changing shutter speed based on the effect you want with the best sensibility and the same aperture. Second, K&F Concept ND2-ND400 lens filter allows creating a blurred background with a large aperture while the shutter speed remains the same. Third, K&F Concept ND2-ND400 lens filter is designed to prevent overexposure and maintain image purity and quality at the same time. *Like a zoom lens, the variable nd filters are suitable for multiple shooting situations. If you're looking for perfect image quality, a fixed ND filter is recommended. 

K&F Concept ND2-ND400 lens filter controls the amount of the light that enters into camera lens with two sets of polarizing glass of high transparency. 

From 1-5 stops, there will be a slight X cross for lens under 24mm. An X cross will appear at the highest stop and can be removed by rotating the filter ring, which is a normal situation instead of a quality issue. 

Tested with Nikon Z 7 and Nikor 14-30mm Sline, dark corners are not obvious for 14mm and no dark corners for 16mm. 

67mm should also be stenciled on the front edge of the lens somewhere. If so, then you should be good to go. It should be on the lens because a lens cap can be lost or broken. 

Look on the lens and it will tell you the size of the filter required,. 

Depends on what you mean by direct sunlight. If you mean the filter pointed directly at the sun, and you are worried about lens flare, well it wont stop that. But if you mean using it out in bright bright sunlight all around, then it works great. I'm a member of the Longview Film Club. We shoot indie short films, and use these for all of lenses and cameras. It's a must when shooting outside under almost any conditions. Makes it possible to get nice Depth of Field even on a sunny day. 

Si amigo si funciona con el sigma 16mm f1.4 porque el diámetro del anillo es de 67 igual. 

Not exactly sure about that lens, but don’t get this version, if you does fit. Get the their no “x” version that they offer for that lens. Not sure why this sell this Style when they offer a better one. Found that out the hard way.