Potter, Paulus: The Wolfhound (1650)

Educational illustrations of contraceptive devices used to include a 50p piece, lying among the caps, coils and condoms, "for scale". This naturally encouraged jokes about the coin's own prophylactic uses. But a 50p wasn't a bad choice as a scale marker. The seven-sided coin is a familiar object, of fixed dimensions, and unlike circular coins, it only comes in one size. There's no mistaking how big it's meant to be.

Scale in paintings is a more complicated, and often more elusive, matter. There are issues of distance and issues of viewpoint to be factored in. We assume that familiar objects are of normal dimensions. We try to make things fit together. But sometimes the artists don't want the relative sizes of things to be decisively fixed. They want to let in a bit of free play and possibility.

Paulus Potter's The Wolfhound is one of the great dog portraits. Like other dog portraits, it shows an ambivalent attitude. It admires the dog both for its domestication and its independence. The dog occupies the frame, commands the scene. No humans are in view to master or upstage it. It is a surrogate human itself. It stands in a presentation pose, in formal profile, in front of its (man-made and artist-signed) house.

But unlike a human portrait, the "sitter" here is chained into its position – the dark links of the chain discreetly but clearly indicated. This bred, trained animal is still a wild beast that must be restrained, and the picture suggests that it lives by itself, on the edge of the land, away from human habitation, supplied with chunks of raw meat (one lies at its feet). It is on watch, looking out of the picture. It is probably a guard dog.

It may also be a monster. Not only are there no bigger humans in view, there is nothing in the picture to establish a definite scale. The solitary hound stands outside its kennel, but such wooden structures come in all sizes. The kennel could be as big as a barn. There's the piece of meat at its feet, but the size of a cut can vary, too. This one might be half a cow. Even the bits of sprouting vegetation can be seen as tall nettles and cow-parsley, not small shrubs.

So turn to the background scene. Again, no clear scale is established. We can see the far bank of a river, a cow drinking, a wood, a settlement with a church, and all these things may be assumed to be normal-sized. But how near or far are they? What we can't see is how the ridge on which the dog stands relates to the river beyond, or how wide that river is. There is no continuous terrain between foreground and background, just a jump. Their distance and their relative scale become unjudgeable. Old films use this jump trick when they want a little model castle, set in front of a real landscape, to look big and real, too. The dog benefits from a similar "special effect". For all we can tell, it could be as big as a horse, or a house.

Crucially, the viewpoint is low. The horizon lies at the level of the hound's leg joints. We're looking up at it. And if we imagine that in this picture, as in many pictures, the viewpoint corresponds to the eye-level of a human standing on the ground, then the dog would be a colossus.

True, it is all a matter of what can be imagined. Literally, the artist hasn't forced or falsified the evidence at all. This could be a realistic image of a normal wolfhound standing in a normal world. It's just that the scene fails to provide any reliable scale markers, and then – with its low viewpoint – it offers a hint as to the creature's gigantic stature. But it's only a hint. This dog could still be normal, and simply viewed somewhat from below.

Metaphorically, on the other hand, the message is clear. This viewpoint makes the dog tower over the horizon, the steeple, the bird in flight. We're to feel that it keeps guard and watch over this domain. Its head is high in the sky. Its nose is keenly in the air.

And see how the fur of the head suddenly darkens, directly against the bright white of the clouds. It makes the hound's profile as sharp as a cut-out silhouette. It becomes the point of maximum tonal contrast in the picture. The sharpness stresses the watchdog's poise, alertness, sensitivity, The darkness gives it an edge of menace.

The artist

Paulus Potter (1625-54) was a specialist, as were many Dutch artists of the 17th-century. Some did landscapes, some still lifes. Potter painted animals, mainly farm animals. In his short life (he died of tuberculosis) he became the most accomplished animalier of his age. A close observer of animal behaviour, he established cows, horses and dogs as subjects deserving of individual depiction, their forms often silhouetted against an open sky. In the 19th century, his life-sized image of a young bull, which looks a bit twee now, was considered one of the star exhibits of Dutch art.