Carl zeiss Jena Biotar 75mm f1.5 is notorious for having different color aberation at different aperture settings under varying lighting conditions.

Solution: shoot custom white balance, or photograph a black/gray/white card at same settings as for picture, or use ExpoDisc.

1) Adjust camera exposure settings

2) Shoot black/gray/white card(coloraid.de or WhiBal)

3) Eye-dropper white from card in gimp ufraw plugin

4) Set "Corrections", "Black Point", in gimp ufraw plugin

5) In gimp, jpeg mode, set "Levels", black/gray/white eye-dropper from coloraid.de color chart.

6) Save levels and quit color chart

7) Load image in gimp ufraw-plugin, ufraw loads last white balance.

8) In gimp jpeg mode, load Levels from file

9) Ad hoc settings: saturate 5 clicks, contrast 3 clicks in gimp jpeg mode, sharpen, unsharp mask