Never one to test gear fairly, my first move with the 350mm Telyt-R was to attach the APO 2x and head out the door under moderate to good light to shoot test targets with the SL2-S. There’s no profile for any R lens with a teleconverter attached, and the profile for the 800mm doesn’t activate IBIS on the SL2-S. Actually, the morning exercise was as much a test of me as it was of the lens.
Center sharpness is as good as any lens I’ve ever used in in the 600-800mm FL range, better than most. The difference between wide open and stopping down, even with the extender, is observable but not worth quibbling about.
Although my hit rate was good with decent shutter speeds (>=1/1.5FL), I could see fuzzy edges in the finest details in most shots taken at anything slower. That’s on me, not on the lens.
Pairing the lens alone with the CL for a too-short afternoon walk, it appeared that feather details are not as evident at middle and farther distances as with APO glass. BUT—and this is a BIG “but”—it has the Mandler look in spades (it was one of his last designs), something I can see in the shots, but which defies description. Unlike the 280mm APO, the effective FL on the CL is within my “sweet spot” range for general birding.
A couple of weeks will tell the full story about this lens, but unless something changes I think the CL has found a new playmate.