95mm ND1000 Filter 10 Stops ND, Solid Neutral Density Lens Filter Multi-Coated Optical Glass Neutral Grey ND with Multi-Resistant Coating Nano-Xcel series

SKU: KF01.1365

A
Yes, there are threads on both sides (I just tried), which can be useful for adding a polarizer. However, you can just as easily have the K&F ND1000 filter stacked onto the inner filter. 
A
Yes you can, I just tested this by screwing on a 82mm polarizer filter. But keep in mind: 1) This can easily cause vignetting with wide angle lenses; 2) colour shifts because of camera sensor reciprocity failure as well as any colour casts inherent to the second filter. 3) Slight resolution and contrast losses. 
A
Canon has at least 7 different 50mm lenses. You need to look on your lens to see what filter size it takes. It'll be written on the lens at the front, beside this symbol: Ø. 
Guess you like products