I'm the proud owner of the Lester A . Dine version created for Dentist
This lens almost defies the imagination in its sharpness & dimensions
I also own the Vivitar 90 - 180 Macro as well & Vivitar 90 2.5
The Kiron 105 & Vivitar 90 are pretty close but I prefer the Kiron
When I need some zooming range for Flowers etc I go to the Vivitar
90 - 180 f 4.5 which is pretty fast but this lens ways almost 3lbs
Usually when I take this lens out it's the only I'll carry 4 the day
I have no problem stopping this lens down but diopter must be right.
Manual Focus is more difficult but my pictures are far better now.
I used to own more AF but only 2 of 20 + are Af