The exercise is to determine the presence and direction of implied lines within a shot be they eye-lines or lines of direction – or both. They are, I think, usually present when there is some form of action or interaction is being photographed.
Like a lot photographs these two ask the viewer to make his or her own decisions on them including where the implied lines are. The implied lines in the bullfight shot are the circular movement of the bull around the matador as indicated by the scuff marks on the stadium floor. Secondly is the implied eyeline of the matador, by necessity, watching the bull. In the second shot there is again an implied line of direction this time of the lead animal towards the right of the frame reinforced by the angle of its movement, There is also an implied eyeline, and possibly a two way one, with the lead animal and the man. not as strong is the possible eyeline between the second animal and either the man or, more likely because of the angle of the head, the lead animal.
This is a sort of double implied line, both forward and reverse. On the one hand the main walker implies a line leading out of the bottom left hand corner of the frame while, on the other, the row of cars take you back into it up to the top right.
Taken at Stowe I like the eye-line from one of its monuments to another. Its not, necessarily a straight line but borders firstly of the columns and secondly of the plants lead the viewer to the far off monument .
The eye-line is fairly obvious here, with the camera and the shadow emphasising it, but there is, arguably, an implied line of sight in the gap between the chairs
Although the face is not visible the obvious interpretation of the shot is that the figure is watching the starting line. Shot at a Rallycross meeting at Lydden Hill, Kent
Here there are three line extensions. The viewer knows that, ordinarily the cars would follow the curve of the track, In this case therefore its possible to extrapolate three lines based on the position of the cars in the photo. Again taken at Lydden Hill.
As with previous exercises there is almost a subliminal instinct to take shots with these eye-lines or lines of direction as they are an important aspect of composition. The shot of the press photographer above for instance without the starting grid of cars in the distance would not, I think be as compositionally strong, Similarly the shot of the three cars would be weaker without some of the frame to go into.