Philips Koninck, 'An Extensive Landscape with a Road by a River', 1655

A strong diagonal path leads from the bottom right of this painting into the middle distance. Standing in front of this large picture it almost feels as though you could clamber down onto it, stroll past the shepherd playing his pipe and follow on the heels of the walker towards the courting couple. When you look closely at these figures, however, you realise that they are not painted to scale. The man walking is further away from us than the shepherd, so should be smaller than him, not bigger. And the two figures a little further down the road are much smaller than they should be.

It is hard to believe that a painter as skilled as Philips Koninck would have made such basic errors of scale by mistake. Instead, what he seems to be doing is experimenting with optical effects, using a deliberate strategy to try to replicate the way our eyes work when we gaze into the distance. Because we can’t focus on an entire panorama at once the eye must either relax altogether, so that everything is slightly blurred, or focus on the detail at a certain point in the distance, so that some of what we see will be clear and the rest slightly fuzzy.

As well as making the walking man in the middle ground more prominent so that he catches our eye, Koninck has painted the landscape around him in a more detailed way. At this distance, the leaves on the trees and shrubs, the sheep and the buildings are carefully articulated. In contrast, the foreground nearest us is suggested with broader brush strokes, as are the fields and buildings in the further distance. The blurring is especially noticeable on the top edge of the bank just below the middle figure. In a real view, there would be a sudden change in the depth of field at this point; if focusing beyond the bank, the top of it would inevitably blur into our peripheral vision.

It’s an innovative technique, but Koninck, who made many large paintings of extensive landscapes, also took a more conventional approach to creating a sense of the vast open space before us. Apart from that diagonal line in the foreground, little distracts the eye from the series of ripple-like horizontals formed by the hedges, fields, patches of water and distant hills. There are no vertical lines, and there is nothing to frame the edges of the panorama. Viewed from such a long, slanting angle, the horizontals seem to run towards us like a series of low waves spreading out from the long flat horizon. Meanwhile, from the same horizon, the clouds billow up towards us at a similar angle, though one which sweeps slightly across the picture from right to left.

The location of this view has not been identified and, like many landscape paintings of the time, it may well be imaginary.