I tried using phi to make the yellow circle, instead of the 0.5 that Bill used, and found that the first version (second image) is a little less well-balanced in comparison with the original. The second version, however, (last image) I think is pretty successful. The smaller the circle, the more the text box comes up – which is what you’d want on a poster. The image would still be seen first from a distance.
I’m assuming Bill was making a geometrical representation of a Zulu shield with his image (the words ‘negerkunst’ and ‘sudafrikas’ are a clue straight away). The smaller version of the circle, then, would perhaps make more sense. It gives the image more space and is clearly smaller than the text box – avoiding any conflict between the two shapes.
No idea why the colours are faded on this screen but if you click on the image, it’s better.