Layman terms: Not CRC, this is an error in judgment. Fits nicely on a Nikon DSLR camera. I own the Nikon Reflex-Nikkor C 500mm F/8 lens and this Nikon 500mm F/8 N version was sent to me to be sold. In hindsight more time should've been given but instead I tested this lens without any help from any sources so that I could not be manipulated into anyones opinion. I made a quick comparison to what I own and with basic understanding of this lens, I made a quick judgement. The only advantage I have found is that with this newer version, the Nikon Reflex-Nikkor 500mm F/8 N lens is that you can shoot closer to your subject.