Minolta Celtic 200mm f4
The Celtic series was Minolta's bargain option. While build quality was excellent image
quality was inferior to Rokkor lenses.
At f4 the 200mm f4 produces low contrast and soft images, which have a substantial amount of chromatic abberration.
At f5.6 it tightens up. Chromatic abberation is greatly reduced though still present. Sharpness is more than acceptable and contrast is excellent. See the tree comparioson. Unfortunately, bokeh fringing is pronounced at all usable apertures. See the mossy rock.
f5.6 - ISO 800
notice blue shift
f4 - ISO 800
f4 (left) - f5.6 (right) - ISO 800