MALE AND FEMALE GOLDFINCHES, GREEN, MICHIGAN, MAY 13, 2015
Pentax-F* 300mm f4.5 plus Pentax HD 1.4x teleconverter (420mm)
Top: 1/400 sec. f6.7
Bottom: 1/250 sec. f6.7
The birds were in deep shade, so I opened the aperture on the F* 300 to the full f4.5 (the teleconverter results in loss of one f/stop, resulting in f/6.7 on the camera). The results were pleasingly sharp.