My Cavision mattebox that once fit perfectly snug over my 14x lens on my HD100 now hovers around a much smaller Canon FD lens. How do you guys adapt mattboxes down to these little lenses? It is rail mounted, but there's a ton of room between the outside of the lens and the inside of the box.

My Cavision mattebox that once fit perfectly snug over my 14x lens on my HD100 now hovers around a much smaller Canon FD lens. How do you guys adapt mattboxes down to these little lenses? It is rail mounted, but there's a ton of room between the outside of the lens and the inside of the box.

I carve a foam insert that covers up most of the extra room. It's not a perfect fit, but it basically blocks the light.

I use step up rings on my Cavision matte box. Since most of my Nikon lenses are 52mm, I have a 52-58 stepup ring and a 58-82mm stepup ring.

I use step up rings on my Cavision matte box. Since most of my Nikon lenses are 52mm, I have a 52-58 stepup ring and a 58-82mm stepup ring.

Ah! Off to the local camera shop for me. Thanks!