Tamron SP 80-200mm f/2.8 ED
OM-4T with mirror and diaphragm prefire

@ 80mm
Distortion: Very slight barrel
Aperture Center Corner Vignetting Contrast
f/2.8    A-     B-     A-         high
f/4      A-     A-     A          mod. high
f/5.6    A      A-     A          mod. high
f/8      A+     A      A          high
f/11     A      A      A          mod. high
f/16     A      A      A          mod. high
f/22     A-     A-     A          moderate
f/32     B      B      A          moderate

@ 120mm
Distortion: None
Aperture Center Corner Vignetting Contrast
f/2.8    B-     B-     B          mod. high
f/4      A-     B+     A          mod. high
f/5.6    B+     B+     A          mod. high
f/8      B+     B+     A          mod. high
f/11     A-     A-     A          high
f/16     A      A-     A          mod. high
f/22     B+     B+     A          mod. high
f/32     B      B      A          mod. high

@ 200mm
Distortion: Moderate pincushion
Aperture Center Corner Vignetting Contrast
f/2.8    B      B      B          mod. high
f/4      A-     B+     A-         mod. high
f/5.6    B+     B+     A          mod. high
f/8      B+     B+     A          mod. high
f/11     A-     A-     A          high
f/16     A-     B+     A          high
f/22     B+     B      A          high
f/32     B      B-     A          mod. high
Notes: Exceptionally easy to focus (using a 2-4 screen) at all focal lengths. 80mm focal length performance rivals the best of prime lenses.

Tamron SP 80-200mm f/2.8 ED IF with Tamron SP 2X Teleconverter
OM-4T with mirror and diaphragm prefire

@ 300mm
Distortion: Slight pincushion
Aperture    Center Corner Vignetting Contrast
f/2.8 (5.6) C      D      A-         med. low
f/4 (8)     B-     C      A-         med. low
f/5.6 (11)  B-     B-     A          med. low
f/8 (16)    B      C+     A          medium
f/11 (22)   B      B-     A          medium
f/16 (32)   B-     B-     A          med. low
f/22 (45)   C+     C+     A          medium
f/32 (64)   D      C-     A          med. low

@ 400mm
Distortion: None
Aperture    Center Corner Vignetting Contrast
f/2.8 (5.6) C*     C-*    A-*        very low*
f/4 (8)     C      C-     A          medium
f/5.6 (11)  B      C+     A          medium
f/8 (16)    B-     C+     A          med. low
f/11 (22)   B      B-     A          medium
f/16 (32)   C+     C+     A          med. low
f/22 (45)   C-     C-     A          med. low
f/32 (64)   Not determined
Notes: * = provisional grade, extremly overexposed slide.