The shoemaker's ball

Unfortunately, your assumption is wrong.

The incident light is focussed onto a smaller area because of the round shape of the ball. If you tried to illuminate the whole room, you would have to spread the incident light.

Certainly you have already tried to read with weak light and you had to exert yourself very hard. Nowadays, we simply adjust our lamps to the desired lighting, in former times one used a simple, physical trick. To work with weak light, which shone from the sun on the work bench, one installed a shoemaker's ball. With the help of such a ball the weak light was bundled, so the craftsman also had a light area for work during twilight.

In what way did the shoemaker's ball have to be installed to achieve the effect in the best way?

a) The shoemaker's ball was installed as closely as possible to the window. In the ideal case on the window sill. Here most of the light reaches the room which can be collected and transmitted by the ball.

b) The shoemaker's ball had to be installed in such a way that it was located in a straight line between the workplace and the incident light. Thus the position of the ball is within the ray path of the light.

c) It was installed as closely as possible to the working material. This was the best way to use its light.