an interesting test found http://members.aol.com/olympusom/lenstests/default.htm
Tokina AT-X 90mm f/2.5 Macro OM-1 with mirror lockup Vignetting = B @ F/2.5, A- @ f/4 Distortion = None Aperture Center Corner f/2.5 B- C f/4 B C+ f/5.6 C B- f/8 C+ B- f/11 B B- f/16 B+ B+ f/22 B+ B+ f/32 B- B Notes: Moderate contrast with lack of resolution. Vivitar Series 1 90mm f/2.5 Macro OM-1 with mirror lockup Vignetting = A- Distortion = none Aperture Center Corner f/2.5 B- C f/4 B B+ f/5.6 B+ A- f/8 A- A- f/11 B+ B f/16 B B f/22 B B Notes: High contrast image. VS1 is high contrast and the other is moderate contast more A- appears than the tokina just found it interesting
