Canon FD 100mm f/2.8 S.S.C. breech mount
Canon F-1 w/ mirror and diaphragm prefire

Vignetting: A- @ f/2.8, A thereafter
Distortion: slight pincushion

Aperture Center Corner
f/2.8    B      B-
f/4      B+     B
f/5.6    B+     B
f/8      B      B-
f/11     B+     B
f/16     B      B-
f/22     B      B-

Notes:
moderate contrast at all focal lengths

Canon FD 100mm f/2.8 S.S.C. breech mount with Canon 2x-A Teleconverter (breech mount)
Canon F1 w/ mirror and diaphragm prefire, same 100mm lens as above

Vignetting: A at all apertures
Distortion: pincushion

Aperture Center Corner
f/2.8 (5.6) C   D
f/4 (8)     B-  C
f/5.6 (11)  B-  C+
f/8 (16)    B   C+
f/11 (22)   B   B-
f/16 (32)   B-  C+
f/22 (44)   C+  C

Notes:
moderately low contrast at f/2.8 (effectively f/5.6);
moderate contrast at f/4 (8) through f/8 (16) and f/16(32) to f/22 (45);
moderately high at f/11 (22).
This is not a recommended combination, since the 2x-B is intended for use with this lens.

Canon FD 100mm f/2.8 S.S.C. breech mount with Canon 2x-B Teleconverter (breech mount)
Canon F1 w/ mirror and diaphragm prefire, same 100mm lens as above

Vignetting: A- @ f/2.8, A thereafter
Distortion: none

Aperture Center Corner
f/2.8 (5.6) B-  C+
f/4 (8)     B   B-
f/5.6 (11)  B+  B
f/8 (16)    B   B-
f/11 (22)   B   B-
f/16 (32)   B-  B-
f/22 (44)   B-  B-

Notes:
moderately low contrast at f/2.8 (effectively f/5.6) and f/22 (45),
moderate contrast at f/4 (8) through f/16 (32).

Canon FD 100mm f/2.8 S.S.C breech mount with Vivitar 2X Macro Focusing Teleconverter
Canon F1 w/ mirror and diaphragm prefire

Vignetting: none
Distortion: none

Aperture Center Corner
f/2.8 (5.6) B-  C
f/4 (8)     B+  B
f/5.6 (11)  A-  B
f/8 (16)    A-  B+
f/11 (22)   B+  B+
f/16 (32)   B   B
f/22 (44)   C+  C+

Notes:
moderately low contrast at f/2.8 (effectively f/5.6),
moderate contrast at f/16 (32) and f/22 (45),
moderately high contrast at f/4 (8) through f/11 (22).