It's a bit pointless to test, say, the big superteles - it's pretty obvious that they're perfect from the get go. The Otus types are probably the same story - but if someone offers to lend you one to test, it'd be nice to see the results (that might even be construed as "reference" in the focal length range).
I think that the Sigma 85mm Art could be considered a reference lens for 5DSR tests by the way. It succeeds in making most (all?) other lenses - even the brand spankin' new Canon 35mm f/1.4 II - look horrible.
I think that the Sigma 85mm Art could be considered a reference lens for 5DSR tests by the way. It succeeds in making most (all?) other lenses - even the brand spankin' new Canon 35mm f/1.4 II - look horrible.