Last chapter in the 800mm saga, the seller offered a substantial discount if I kept the lens, so I decided to keep it if it was truly sharp corner to corner, and it is! if you nail focus it is sharpest fully open.
So it will stay with me after all.
I accept the uneven lower left corner illumination, at this level with same vivid processing as the pics above. Glass is pristine so no idea what causes this.
