Quote Originally Posted by dodphotography View Post
do you think there is a noticeable difference between the C and newer KL version?
Just to clarify, there was never a K/L version made in RB mount (mechanical shutter) - only a Sekor-C version. The Sekor-Z version for the RZ system appears to be optically identical (based on studying all the optical diagrams I could find) simply with an electronic shutter. As Ed said, it may have revised coatings (though the flare-resistance of the C version is extraordinary already, difficult to improve upon!)