How to install neutral filter for the fish-eye lens?

Dear List:
I am practicing taking HDR images of the window in the day-lit room. I use Canon EOS 6D with a SIGMA 8mm f/3.5 EX DG fisheye lens.When the sun occurs in the view, I am suggested to put a Koda
neutral density filter 3 between the camera and the lens before taking an image. But the issue is that I don’t know how to install the filter as the filter is square and large. What is the solution to this problem?
Any suggestion is appreciated. Thank you !

Hi Lee,

The back of the lens (which faces the camera when the lens is attached) has a slot that you can slide the filter into. You will need scissors to cut the filter down to a size that will fit into the slot.


Hello Nathaniel:
Thank you very much for your reply. But I am a little concerned about the glass filter(not Koda) which is fragile using the scissors. Perhaps the Koda neutral density filter 3 is not glass and easy to cut?

Hi Lee,

The Kodak Wratten filters are plastic squares and easily cut down to size. Last I purchased some, they were a bit hard to find however.


Hi Alstan,
Thanks for your reply. How do you purchase the filters ? I haven’t find any website which sells new ones except the used. Can you share some information about it? Besides, is there any alternative to Kodak of the same material ?

I ordered them through an ‘optics’ website. I don’t have much more guidance than that unfortunately – this was several years ago.

Hi Alstan,
I have found a website that sells the filters. I plan to cut a circle with the scissors.