If I remember the issue, Modern Photography tested the 90mm f/2.5 Vivitar Series 1 when it first came out and declared it to be the sharpest lens it had ever tested. I have the 90/2.5 Series 1 lens in Canon FD mount. Over time I have accumulated many other Canon mount macro lenses in this range. These include two Vivitar 100/2.8 (22XXX...), three versions of the Cosina-made 100/3.5: Vivitar, ProMaster and Phoenix and two other lenses which can be used on the Canon FD cameras. These are the Tamron 90/2.5 SP (2nd verison) and a 100/4 Canon FLM bellows lens. All of these are good lenses. My favorite is still the 90/2.5 Series 1 but I am mostly using one of the 100/2.8 Vivitars and one of the 100/3.5 Cosina-made lenses. The 100/2.8 will reach 1:1 without additional extension and the 100/3.5 lenses are nice and light. I would say that the 100/2.8 has more modern coating than the older 90/2.5 Series 1. The rokkorfiles website tested the 100/3.5MC Rokkor macro lens against the newer f/4 model and found the f/4 lens to be slightly better. I also have many macro lenses in Minolta mount but I don't have either of these Rokkors. My 100/4 Bellows Rokkor-X is supposed to have the same formula as the 100/4 with the focusing mount. It is a very good lens but not as convenient for many purposes as my other Minolta mount macro lenses with focusing mounts.