Canon MP-E 65/2.8, anyone?
Originally Posted by dynachrome
There's another artificial but somewhat useful and widely adopted dichotomy: photography at magnifications <= 1:1 is closeup photography, at magnifications > 1:1 is photomacrography. If you buy this, lenses for use above 1:1 are macro lenses, regardless of mounting hardware.
All lenses are optimized for relatively limited ranges of magnifications. Some types, usually but not always fairly symmetrical, hold their optimizations well, if not perfectly, at all distances.
Funny, the handful of 100/6.3 Luminars I've used are not in M39x26tpi and neither is my 100/6.3 Neupolar, a somewhat better lens.
Moral of this post? If you're going to lay down the law, be right.